| Arizona Plants Checklist 2008 | |||
| Data Source: USDA, NRCS. 2008. The PLANTS Database (http://plants.usda.gov, 3 February 2008).
National Plant Data Center, Baton Rouge, LA 70874-4490 USA. |
|||
| Scientific Name | Common Name | Family | |
| A | |||
| Abies | fir | Pinaceae | |
| Abies concolor | white fir | Pinaceae | |
| Abies concolor var. concolor | white fir | Pinaceae | |
| Abies lasiocarpa | subalpine fir | Pinaceae | |
| Abies lasiocarpa var. arizonica | corkbark fir | Pinaceae | |
| Abies lasiocarpa var. lasiocarpa | subalpine fir | Pinaceae | |
| Abronia | sand verbena | Nyctaginaceae | |
| Abronia angustifolia | purple sand verbena | Nyctaginaceae | |
| Abronia elliptica | fragrant white sand verbena | Nyctaginaceae | |
| Abronia fragrans | snowball sand verbena | Nyctaginaceae | |
| Abronia nana | dwarf sand verbena | Nyctaginaceae | |
| Abronia nana var. nana | dwarf sand verbena | Nyctaginaceae | |
| Abronia villosa | desert sand verbena | Nyctaginaceae | |
| Abronia villosa var. aurita | desert sand verbena | Nyctaginaceae | |
| Abronia villosa var. villosa | desert sand verbena | Nyctaginaceae | |
| Abutilon | Indian mallow | Malvaceae | |
| Abutilon abutiloides | shrubby Indian mallow | Malvaceae | |
| Abutilon incanum | pelotazo | Malvaceae | |
| Abutilon malacum | yellow Indian mallow | Malvaceae | |
| Abutilon mollicomum | Sonoran Indian mallow | Malvaceae | |
| Abutilon palmeri | Palmer's Indian mallow | Malvaceae | |
| Abutilon parishii | Parish's Indian mallow | Malvaceae | |
| Abutilon parvulum | dwarf Indian mallow | Malvaceae | |
| Abutilon reventum | yellowflower Indian mallow | Malvaceae | |
| Abutilon theophrasti | velvetleaf | Malvaceae | |
| Abutilon thurberi | Thurber's Indian mallow | Malvaceae | |
| Acacia | acacia | Fabaceae | |
| Acacia angustissima | prairie acacia | Fabaceae | |
| Acacia angustissima var. shrevei | Shreve's prairie acacia | Fabaceae | |
| Acacia angustissima var. suffrutescens | prairie acacia | Fabaceae | |
| Acacia angustissima var. texensis | prairie wattle | Fabaceae | |
| Acacia constricta | whitethorn acacia | Fabaceae | |
| Acacia constricta var. constricta | whitethorn acacia | Fabaceae | |
| Acacia constricta var. paucispina | whitethorn acacia | Fabaceae | |
| Acacia farnesiana | sweet acacia | Fabaceae | |
| Acacia greggii | catclaw acacia | Fabaceae | |
| Acacia greggii var. greggii | catclaw acacia | Fabaceae | |
| Acacia millefolia | milfoil wattle | Fabaceae | |
| Acacia neovernicosa | viscid acacia | Fabaceae | |
| Acacia redolens | bank catclaw | Fabaceae | |
| Acalypha | copperleaf | Euphorbiaceae | |
| Acalypha californica | California copperleaf | Euphorbiaceae | |
| Acalypha mexicana | Mexican copperleaf | Euphorbiaceae | |
| Acalypha neomexicana | New Mexico copperleaf | Euphorbiaceae | |
| Acalypha ostryifolia | pineland threeseed mercury | Euphorbiaceae | |
| Acalypha phleoides | shrubby copperleaf | Euphorbiaceae | |
| Acamptopappus | goldenhead | Asteraceae | |
| Acamptopappus sphaerocephalus | rayless goldenhead | Asteraceae | |
| Acamptopappus sphaerocephalus var. hirtellus | rayless goldenhead | Asteraceae | |
| Acamptopappus sphaerocephalus var. sphaerocephalus | rayless goldenhead | Asteraceae | |
| Acer | maple | Aceraceae | |
| Acer glabrum | Rocky Mountain maple | Aceraceae | |
| Acer glabrum var. diffusum | Rocky Mountain maple | Aceraceae | |
| Acer glabrum var. glabrum | Rocky Mountain maple | Aceraceae | |
| Acer glabrum var. neomexicanum | New Mexico maple | Aceraceae | |
| Acer grandidentatum | bigtooth maple | Aceraceae | |
| Acer grandidentatum var. grandidentatum | bigtooth maple | Aceraceae | |
| Acer grandidentatum var. sinuosum | canyon maple | Aceraceae | |
| Acer negundo | boxelder | Aceraceae | |
| Acer negundo var. arizonicum | Arizona boxelder | Aceraceae | |
| Acer negundo var. interius | boxelder | Aceraceae | |
| Achillea | yarrow | Asteraceae | |
| Achillea millefolium | common yarrow | Asteraceae | |
| Achillea millefolium var. alpicola | common yarrow | Asteraceae | |
| Achillea millefolium var. occidentalis | western yarrow | Asteraceae | |
| Achnatherum | needlegrass | Poaceae | |
| Achnatherum aridum | Mormon needlegrass | Poaceae | |
| Achnatherum bloomeri | Poaceae | ||
| Achnatherum eminens | southwestern needlegrass | Poaceae | |
| Achnatherum hymenoides | Indian ricegrass | Poaceae | |
| Achnatherum lemmonii | Lemmon's needlegrass | Poaceae | |
| Achnatherum lemmonii var. lemmonii | Lemmon's needlegrass | Poaceae | |
| Achnatherum lettermanii | Letterman's needlegrass | Poaceae | |
| Achnatherum lobatum | littleawn needlegrass | Poaceae | |
| Achnatherum nelsonii | Columbia needlegrass | Poaceae | |
| Achnatherum nelsonii ssp. dorei | Dore's needlegrass | Poaceae | |
| Achnatherum nelsonii ssp. nelsonii | Columbia needlegrass | Poaceae | |
| Achnatherum occidentale | western needlegrass | Poaceae | |
| Achnatherum occidentale ssp. pubescens | pubescent western needlegrass | Poaceae | |
| Achnatherum parishii | Parish's needlegrass | Poaceae | |
| Achnatherum parishii var. parishii | Parish's needlegrass | Poaceae | |
| Achnatherum perplexum | New Mexico needlegrass | Poaceae | |
| Achnatherum pinetorum | pine needlegrass | Poaceae | |
| Achnatherum robustum | sleepygrass | Poaceae | |
| Achnatherum speciosum | desert needlegrass | Poaceae | |
| Achyronychia | achyronychia | Caryophyllaceae | |
| Achyronychia cooperi | onyxflower | Caryophyllaceae | |
| Acleisanthes | trumpets | Nyctaginaceae | |
| Acleisanthes longiflora | angel's trumpets | Nyctaginaceae | |
| Aconitum | monkshood | Ranunculaceae | |
| Aconitum columbianum | Columbian monkshood | Ranunculaceae | |
| Aconitum columbianum ssp. columbianum | Columbian monkshood | Ranunculaceae | |
| Aconitum infectum | Arizona monkshood | Ranunculaceae | |
| Acourtia | desertpeony | Asteraceae | |
| Acourtia nana | dwarf desertpeony | Asteraceae | |
| Acourtia thurberi | Thurber's desertpeony | Asteraceae | |
| Acourtia wrightii | brownfoot | Asteraceae | |
| Acroptilon | hardheads | Asteraceae | |
| Acroptilon repens | hardheads | Asteraceae | |
| Actaea | baneberry | Ranunculaceae | |
| Actaea arizonica | Arizona bugbane | Ranunculaceae | |
| Actaea rubra | red baneberry | Ranunculaceae | |
| Actaea rubra ssp. arguta | red baneberry | Ranunculaceae | |
| Adenophyllum | dogweed | Asteraceae | |
| Adenophyllum cooperi | Cooper's dogweed | Asteraceae | |
| Adenophyllum porophylloides | San Felipe dogweed | Asteraceae | |
| Adenophyllum porophyllum | poreleaf dogweed | Asteraceae | |
| Adenophyllum wrightii | Wright's dogweed | Asteraceae | |
| Adiantum | maidenhair fern | Pteridaceae | |
| Adiantum aleuticum | Aleutian maidenhair | Pteridaceae | |
| Adiantum capillus-veneris | common maidenhair | Pteridaceae | |
| Aegilops | goatgrass | Poaceae | |
| Aegilops cylindrica | jointed goatgrass | Poaceae | |
| Aegilops tauschii | Tausch's goatgrass | Poaceae | |
| Aegopogon | relaxgrass | Poaceae | |
| Aegopogon tenellus | fragilegrass | Poaceae | |
| Aeluropus | Poaceae | ||
| Aeluropus littoralis | Poaceae | ||
| Aeschynomene | jointvetch | Fabaceae | |
| Aeschynomene villosa | hairy jointvetch | Fabaceae | |
| Agastache | giant hyssop | Lamiaceae | |
| Agastache breviflora | Trans-Pecos giant hyssop | Lamiaceae | |
| Agastache micrantha | white giant hyssop | Lamiaceae | |
| Agastache pallida | pale giant hyssop | Lamiaceae | |
| Agastache pallidiflora | Bill Williams Mountain giant hyssop | Lamiaceae | |
| Agastache pallidiflora ssp. pallidiflora | Bill Williams Mountain giant hyssop | Lamiaceae | |
| Agastache pallidiflora ssp. pallidiflora var. gilensis | Bill Williams Mountain giant hyssop | Lamiaceae | |
| Agastache pallidiflora ssp. pallidiflora var. greenei | Bill Williams Mountain giant hyssop | Lamiaceae | |
| Agastache pallidiflora ssp. pallidiflora var. pallidiflora | Bill Williams Mountain giant hyssop | Lamiaceae | |
| Agastache rupestris | threadleaf giant hyssop | Lamiaceae | |
| Agastache wrightii | Sonoran giant hyssop | Lamiaceae | |
| Agave | agave | Agavaceae | |
| Agave ajoensis | Agavaceae | ||
| Agave americana | American century plant | Agavaceae | |
| Agave americana ssp. americana | American century plant | Agavaceae | |
| Agave americana ssp. americana var. expansa | American century plant | Agavaceae | |
| Agave arizonica | Arizona century plant | Agavaceae | |
| Agave chrysantha | goldenflower century plant | Agavaceae | |
| Agave delamateri | Tonto Basin century plant | Agavaceae | |
| Agave deserti | desert agave | Agavaceae | |
| Agave deserti ssp. simplex | desert agave | Agavaceae | |
| Agave murpheyi | Murphey's century plant | Agavaceae | |
| Agave palmeri | Palmer's century plant | Agavaceae | |
| Agave parryi | Parry's agave | Agavaceae | |
| Agave parryi ssp. parryi | Parry's agave | Agavaceae | |
| Agave parviflora | smallflower century plant | Agavaceae | |
| Agave phillipsiana | Grand Canyon century plant | Agavaceae | |
| Agave schottii | Schott's century plant | Agavaceae | |
| Agave schottii var. schottii | Schott's century plant | Agavaceae | |
| Agave schottii var. treleasei | Trelease's century plant | Agavaceae | |
| Agave toumeyana | Toumey's century plant | Agavaceae | |
| Agave toumeyana var. bella | Toumey's century plant | Agavaceae | |
| Agave toumeyana var. toumeyana | Toumey's century plant | Agavaceae | |
| Agave univittata | McKelvey's century plant | Agavaceae | |
| Agave utahensis | Utah agave | Agavaceae | |
| Agave utahensis var. kaibabensis | Kaibab agave | Agavaceae | |
| Agave utahensis var. utahensis | Utah agave | Agavaceae | |
| Ageratina | snakeroot | Asteraceae | |
| Ageratina herbacea | fragrant snakeroot | Asteraceae | |
| Ageratina lemmonii | Lemmon's snakeroot | Asteraceae | |
| Ageratina paupercula | Santa Rita snakeroot | Asteraceae | |
| Ageratina rothrockii | Rothrock's snakeroot | Asteraceae | |
| Ageratina wrightii | Wright's snakeroot | Asteraceae | |
| Ageratum | whiteweed | Asteraceae | |
| Ageratum corymbosum | flat-top whiteweed | Asteraceae | |
| Agoseris | agoseris | Asteraceae | |
| Agoseris aurantiaca | orange agoseris | Asteraceae | |
| Agoseris aurantiaca var. purpurea | orange agoseris | Asteraceae | |
| Agoseris glauca | pale agoseris | Asteraceae | |
| Agoseris glauca var. dasycephala | pale agoseris | Asteraceae | |
| Agoseris glauca var. glauca | pale agoseris | Asteraceae | |
| Agoseris glauca var. laciniata | false agoseris | Asteraceae | |
| Agoseris heterophylla | annual agoseris | Asteraceae | |
| Agoseris heterophylla var. heterophylla | annual agoseris | Asteraceae | |
| Agrimonia | agrimony | Rosaceae | |
| Agrimonia gryposepala | tall hairy agrimony | Rosaceae | |
| Agrimonia striata | roadside agrimony | Rosaceae | |
| Agropyron | wheatgrass | Poaceae | |
| Agropyron desertorum | desert wheatgrass | Poaceae | |
| Agrostis | bentgrass | Poaceae | |
| Agrostis elliottiana | Elliott's bentgrass | Poaceae | |
| Agrostis exarata | spike bentgrass | Poaceae | |
| Agrostis gigantea | redtop | Poaceae | |
| Agrostis idahoensis | Idaho bentgrass | Poaceae | |
| Agrostis scabra | rough bentgrass | Poaceae | |
| Agrostis stolonifera | creeping bentgrass | Poaceae | |
| Ailanthus | ailanthus | Simaroubaceae | |
| Ailanthus altissima | tree of heaven | Simaroubaceae | |
| Albizia | albizia | Fabaceae | |
| Albizia julibrissin | silktree | Fabaceae | |
| Aletes | Indian parsley | Apiaceae | |
| Aletes macdougalii | MacDougal's Indian parsley | Apiaceae | |
| Aletes macdougalii ssp. macdougalii | MacDougal's Indian parsley | Apiaceae | |
| Aletes sessiliflorus | sessileflower Indian parsley | Apiaceae | |
| Alhagi | alhagi | Fabaceae | |
| Alhagi maurorum | camelthorn | Fabaceae | |
| Aliciella | Polemoniaceae | ||
| Aliciella hutchinsifolia | desert pale gilia | Polemoniaceae | |
| Aliciella latifolia | broad-leaf gilia | Polemoniaceae | |
| Aliciella latifolia ssp. latifolia | broadleaf gilia | Polemoniaceae | |
| Aliciella leptomeria | sand gilia | Polemoniaceae | |
| Aliciella lottiae | Lott's gilia | Polemoniaceae | |
| Aliciella subacaulis | pinyon gilia | Polemoniaceae | |
| Aliciella subnuda | coral gilia | Polemoniaceae | |
| Aliciella triodon | coyote gilia | Polemoniaceae | |
| Alisma | water plantain | Alismataceae | |
| Alisma gramineum | narrowleaf water plantain | Alismataceae | |
| Alisma subcordatum | American water plantain | Alismataceae | |
| Alisma triviale | northern water plantain | Alismataceae | |
| Allenrolfea | allenrolfea | Chenopodiaceae | |
| Allenrolfea occidentalis | iodinebush | Chenopodiaceae | |
| Allionia | windmills | Nyctaginaceae | |
| Allionia choisyi | annual windmills | Nyctaginaceae | |
| Allionia incarnata | trailing windmills | Nyctaginaceae | |
| Allionia incarnata var. incarnata | trailing windmills | Nyctaginaceae | |
| Allionia incarnata var. nudata | trailing windmills | Nyctaginaceae | |
| Allionia incarnata var. villosa | trailing windmills | Nyctaginaceae | |
| Allium | onion | Liliaceae | |
| Allium acuminatum | tapertip onion | Liliaceae | |
| Allium atrorubens | darkred onion | Liliaceae | |
| Allium atrorubens var. atrorubens | darkred onion | Liliaceae | |
| Allium atrorubens var. cristatum | darkred onion | Liliaceae | |
| Allium bigelovii | Bigelow's onion | Liliaceae | |
| Allium bisceptrum | twincrest onion | Liliaceae | |
| Allium bisceptrum var. palmeri | aspen onion | Liliaceae | |
| Allium cernuum | nodding onion | Liliaceae | |
| Allium cernuum var. neomexicanum | New Mexican nodding onion | Liliaceae | |
| Allium cernuum var. obtusum | nodding onion | Liliaceae | |
| Allium geyeri | Geyer's onion | Liliaceae | |
| Allium geyeri var. geyeri | Geyer's onion | Liliaceae | |
| Allium geyeri var. tenerum | bulbil onion | Liliaceae | |
| Allium glandulosum | gland onion | Liliaceae | |
| Allium gooddingii | Goodding's onion | Liliaceae | |
| Allium kunthii | Kunth's onion | Liliaceae | |
| Allium macropetalum | largeflower onion | Liliaceae | |
| Allium nevadense | Nevada onion | Liliaceae | |
| Allium parishii | Parish's onion | Liliaceae | |
| Allium plummerae | Tanners Canyon onion | Liliaceae | |
| Allophyllum | false gilyflower | Polemoniaceae | |
| Allophyllum gilioides | dense false gilyflower | Polemoniaceae | |
| Allophyllum gilioides ssp. gilioides | dense false gilyflower | Polemoniaceae | |
| Almutaster | alkali marsh aster | Asteraceae | |
| Almutaster pauciflorus | alkali marsh aster | Asteraceae | |
| Alnus | alder | Betulaceae | |
| Alnus incana | gray alder | Betulaceae | |
| Alnus incana ssp. tenuifolia | thinleaf alder | Betulaceae | |
| Alnus oblongifolia | Arizona alder | Betulaceae | |
| Alopecurus | foxtail | Poaceae | |
| Alopecurus aequalis | shortawn foxtail | Poaceae | |
| Alopecurus aequalis var. aequalis | shortawn foxtail | Poaceae | |
| Alopecurus arundinaceus | creeping meadow foxtail | Poaceae | |
| Alopecurus carolinianus | Carolina foxtail | Poaceae | |
| Alopecurus geniculatus | water foxtail | Poaceae | |
| Alopecurus geniculatus var. geniculatus | water foxtail | Poaceae | |
| Aloysia | beebrush | Verbenaceae | |
| Aloysia gratissima | whitebrush | Verbenaceae | |
| Aloysia gratissima var. schulziae | whitebrush | Verbenaceae | |
| Aloysia wrightii | Wright's beebrush | Verbenaceae | |
| Alternanthera | joyweed | Amaranthaceae | |
| Alternanthera caracasana | washerwoman | Amaranthaceae | |
| Amaranthus | pigweed | Amaranthaceae | |
| Amaranthus acanthochiton | greenstripe | Amaranthaceae | |
| Amaranthus albus | prostrate pigweed | Amaranthaceae | |
| Amaranthus blitoides | mat amaranth | Amaranthaceae | |
| Amaranthus caudatus | love-lies-bleeding | Amaranthaceae | |
| Amaranthus crassipes | spreading amaranth | Amaranthaceae | |
| Amaranthus crassipes var. crassipes | spreading amaranth | Amaranthaceae | |
| Amaranthus cruentus | red amaranth | Amaranthaceae | |
| Amaranthus fimbriatus | fringed amaranth | Amaranthaceae | |
| Amaranthus hybridus | slim amaranth | Amaranthaceae | |
| Amaranthus hypochondriacus | Prince-of-Wales feather | Amaranthaceae | |
| Amaranthus obcordatus | Trans-Pecos amaranth | Amaranthaceae | |
| Amaranthus palmeri | carelessweed | Amaranthaceae | |
| Amaranthus powellii | Powell's amaranth | Amaranthaceae | |
| Amaranthus powellii ssp. powellii | Powell's amaranth | Amaranthaceae | |
| Amaranthus pringlei | Pringle's amaranth | Amaranthaceae | |
| Amaranthus retroflexus | redroot amaranth | Amaranthaceae | |
| Amaranthus torreyi | Torrey's amaranthus | Amaranthaceae | |
| Amaranthus tucsonensis | Amaranthaceae | ||
| Amaranthus venulosus | fringed amaranth | Amaranthaceae | |
| Amaranthus viridis | slender amaranth | Amaranthaceae | |
| Amaranthus watsonii | Watson's amaranth | Amaranthaceae | |
| Amaranthus wrightii | Wright's amaranth | Amaranthaceae | |
| Ambrosia | ragweed | Asteraceae | |
| Ambrosia acanthicarpa | flatspine bur ragweed | Asteraceae | |
| Ambrosia ambrosioides | ambrosia leaf bur ragweed | Asteraceae | |
| Ambrosia artemisiifolia | annual ragweed | Asteraceae | |
| Ambrosia artemisiifolia var. elatior | annual ragweed | Asteraceae | |
| Ambrosia canescens | hairy ragweed | Asteraceae | |
| Ambrosia confertiflora | weakleaf bur ragweed | Asteraceae | |
| Ambrosia cordifolia | Tucson bur ragweed | Asteraceae | |
| Ambrosia deltoidea | triangle bur ragweed | Asteraceae | |
| Ambrosia dumosa | burrobush | Asteraceae | |
| Ambrosia eriocentra | woolly fruit bur ragweed | Asteraceae | |
| Ambrosia ilicifolia | hollyleaf bur ragweed | Asteraceae | |
| Ambrosia psilostachya | Cuman ragweed | Asteraceae | |
| Ambrosia tomentosa | skeletonleaf bur ragweed | Asteraceae | |
| Ambrosia trifida | great ragweed | Asteraceae | |
| Ambrosia trifida var. texana | Texan great ragweed | Asteraceae | |
| Ambrosia trifida var. trifida | great ragweed | Asteraceae | |
| Amelanchier | serviceberry | Rosaceae | |
| Amelanchier pumila | dwarf serviceberry | Rosaceae | |
| Amelanchier utahensis | Utah serviceberry | Rosaceae | |
| Amelanchier utahensis var. covillei | Coville's serviceberry | Rosaceae | |
| Amelanchier utahensis var. utahensis | Utah serviceberry | Rosaceae | |
| Ammannia | redstem | Lythraceae | |
| Ammannia auriculata | eared redstem | Lythraceae | |
| Ammannia coccinea | valley redstem | Lythraceae | |
| Ammannia robusta | grand redstem | Lythraceae | |
| Ammi | ammi | Apiaceae | |
| Ammi majus | large bullwort | Apiaceae | |
| Ammocodon | ammocodon | Nyctaginaceae | |
| Ammocodon chenopodioides | goosefoot moonpod | Nyctaginaceae | |
| Ammoselinum | sandparsley | Apiaceae | |
| Ammoselinum giganteum | western sandparsley | Apiaceae | |
| Amoreuxia | yellowshow | Bixaceae | |
| Amoreuxia gonzalezii | Santa Rita mountain yellowshow | Bixaceae | |
| Amoreuxia palmatifida | Mexican yellowshow | Bixaceae | |
| Amorpha | false indigo | Fabaceae | |
| Amorpha californica | California false indigo | Fabaceae | |
| Amorpha californica var. californica | California false indigo | Fabaceae | |
| Amorpha fruticosa | desert false indigo | Fabaceae | |
| Amphipappus | chaffbush | Asteraceae | |
| Amphipappus fremontii | Fremont's chaffbush | Asteraceae | |
| Amphipappus fremontii ssp. spinosus | Fremont's chaffbush | Asteraceae | |
| Amsinckia | fiddleneck | Boraginaceae | |
| Amsinckia menziesii | Menzies' fiddleneck | Boraginaceae | |
| Amsinckia menziesii var. intermedia | common fiddleneck | Boraginaceae | |
| Amsinckia tessellata | bristly fiddleneck | Boraginaceae | |
| Amsinckia tessellata var. tessellata | bristly fiddleneck | Boraginaceae | |
| Amsonia | bluestar | Apocynaceae | |
| Amsonia grandiflora | Arizona bluestar | Apocynaceae | |
| Amsonia jonesii | Jones' bluestar | Apocynaceae | |
| Amsonia kearneyana | Kearney's bluestar | Apocynaceae | |
| Amsonia longiflora | tubular bluestar | Apocynaceae | |
| Amsonia longiflora var. longiflora | tubular bluestar | Apocynaceae | |
| Amsonia palmeri | Palmer's bluestar | Apocynaceae | |
| Amsonia peeblesii | Peebles' bluestar | Apocynaceae | |
| Amsonia tomentosa | woolly bluestar | Apocynaceae | |
| Amsonia tomentosa var. stenophylla | woolly bluestar | Apocynaceae | |
| Amsonia tomentosa var. tomentosa | woolly bluestar | Apocynaceae | |
| Anagallis | pimpernel | Primulaceae | |
| Anagallis arvensis | scarlet pimpernel | Primulaceae | |
| Anagallis arvensis ssp. arvensis | scarlet pimpernel | Primulaceae | |
| Anagallis minima | chaffweed | Primulaceae | |
| Anaphalis | pearly everlasting | Asteraceae | |
| Anaphalis margaritacea | western pearly everlasting | Asteraceae | |
| Andropogon | bluestem | Poaceae | |
| Andropogon gerardii | big bluestem | Poaceae | |
| Andropogon glomeratus | bushy bluestem | Poaceae | |
| Andropogon glomeratus var. pumilus | bushy bluestem | Poaceae | |
| Andropogon hallii | sand bluestem | Poaceae | |
| Androsace | rockjasmine | Primulaceae | |
| Androsace occidentalis | western rockjasmine | Primulaceae | |
| Androsace septentrionalis | pygmyflower rockjasmine | Primulaceae | |
| Androsace septentrionalis ssp. glandulosa | pygmyflower rockjasmine | Primulaceae | |
| Androsace septentrionalis ssp. puberulenta | pygmyflower rockjasmine | Primulaceae | |
| Androsace septentrionalis ssp. subulifera | pygmyflower rockjasmine | Primulaceae | |
| Androstephium | funnel lily | Liliaceae | |
| Androstephium breviflorum | pink funnel lily | Liliaceae | |
| Anemone | anemone | Ranunculaceae | |
| Anemone cylindrica | candle anemone | Ranunculaceae | |
| Anemone multifida | Pacific anemone | Ranunculaceae | |
| Anemone multifida var. multifida | Pacific anemone | Ranunculaceae | |
| Anemone multifida var. stylosa | Pacific anemone | Ranunculaceae | |
| Anemone tuberosa | tuber anemone | Ranunculaceae | |
| Anemone tuberosa var. tuberosa | tuber anemone | Ranunculaceae | |
| Anemopsis | yerba mansa | Saururaceae | |
| Anemopsis californica | yerba mansa | Saururaceae | |
| Anethum | dill | Apiaceae | |
| Anethum graveolens | dill | Apiaceae | |
| Angelica | angelica | Apiaceae | |
| Angelica pinnata | small-leaf angelica | Apiaceae | |
| Anisacanthus | desert honeysuckle | Acanthaceae | |
| Anisacanthus thurberi | Thurber's desert honeysuckle | Acanthaceae | |
| Anisocoma | anisocoma | Asteraceae | |
| Anisocoma acaulis | scalebud | Asteraceae | |
| Anoda | anoda | Malvaceae | |
| Anoda abutiloides | Indian anoda | Malvaceae | |
| Anoda crenatiflora | thicket anoda | Malvaceae | |
| Anoda cristata | crested anoda | Malvaceae | |
| Anoda lanceolata | lanceleaf anoda | Malvaceae | |
| Anoda pentaschista | field anoda | Malvaceae | |
| Anoda reticulata | netted anoda | Malvaceae | |
| Anoda thurberi | Arizona anoda | Malvaceae | |
| Antennaria | pussytoes | Asteraceae | |
| Antennaria marginata | whitemargin pussytoes | Asteraceae | |
| Antennaria media | Rocky Mountain pussytoes | Asteraceae | |
| Antennaria microphylla | littleleaf pussytoes | Asteraceae | |
| Antennaria parvifolia | small-leaf pussytoes | Asteraceae | |
| Antennaria rosea | rosy pussytoes | Asteraceae | |
| Antennaria rosea ssp. arida | rosy pussytoes | Asteraceae | |
| Antennaria rosea ssp. confinis | rosy pussytoes | Asteraceae | |
| Antennaria rosea ssp. pulvinata | pulvinate pussytoes | Asteraceae | |
| Antennaria rosulata | Kaibab pussytoes | Asteraceae | |
| Anthemis | chamomile | Asteraceae | |
| Anthemis cotula | stinking chamomile | Asteraceae | |
| Antheropeas | easterbonnets | Asteraceae | |
| Antheropeas lanosum | white easterbonnets | Asteraceae | |
| Antheropeas wallacei | woolly easterbonnets | Asteraceae | |
| Anthriscus | chervil | Apiaceae | |
| Anthriscus caucalis | bur chervil | Apiaceae | |
| Anulocaulis | ringstem | Nyctaginaceae | |
| Anulocaulis leiosolenus | southwestern ringstem | Nyctaginaceae | |
| Anulocaulis leiosolenus var. leiosolenus | southwestern ringstem | Nyctaginaceae | |
| Apacheria | apacheria | Crossosomataceae | |
| Apacheria chiricahuensis | apachebush | Crossosomataceae | |
| Apera | silkybent | Poaceae | |
| Apera interrupta | dense silkybent | Poaceae | |
| Aphanostephus | dozedaisy | Asteraceae | |
| Aphanostephus ramosissimus | plains dozedaisy | Asteraceae | |
| Aphanostephus ramosissimus var. humilis | plains dozedaisy | Asteraceae | |
| Apiastrum | apiastrum | Apiaceae | |
| Apiastrum angustifolium | mock parsley | Apiaceae | |
| Apium | celery | Apiaceae | |
| Apium graveolens | wild celery | Apiaceae | |
| Apium graveolens var. dulce | wild celery | Apiaceae | |
| Aplectrum | Adam and Eve | Orchidaceae | |
| Aplectrum hyemale | Adam and Eve | Orchidaceae | |
| Apocynum | dogbane | Apocynaceae | |
| Apocynum androsaemifolium | spreading dogbane | Apocynaceae | |
| Apocynum cannabinum | Indianhemp | Apocynaceae | |
| Apocynum floribundum | Apocynaceae | ||
| Apodanthera | apodanthera | Cucurbitaceae | |
| Apodanthera undulata | melon loco | Cucurbitaceae | |
| Aquilegia | columbine | Ranunculaceae | |
| Aquilegia chrysantha | golden columbine | Ranunculaceae | |
| Aquilegia chrysantha var. chrysantha | golden columbine | Ranunculaceae | |
| Aquilegia chrysantha var. rydbergii | Rydberg's golden columbine | Ranunculaceae | |
| Aquilegia coerulea | Colorado blue columbine | Ranunculaceae | |
| Aquilegia coerulea var. pinetorum | Colorado blue columbine | Ranunculaceae | |
| Aquilegia desertorum | desert columbine | Ranunculaceae | |
| Aquilegia elegantula | western red columbine | Ranunculaceae | |
| Aquilegia longissima | longspur columbine | Ranunculaceae | |
| Aquilegia micrantha | Mancos columbine | Ranunculaceae | |
| Aquilegia micrantha var. micrantha | Mancos columbine | Ranunculaceae | |
| Aquilegia triternata | Chiricahua Mountain columbine | Ranunculaceae | |
| Arabis | rockcress | Brassicaceae | |
| Arabis drummondii | Drummond's rockcress | Brassicaceae | |
| Arabis fendleri | Fendler's rockcress | Brassicaceae | |
| Arabis fendleri var. fendleri | Fendler's rockcress | Brassicaceae | |
| Arabis glabra | tower rockcress | Brassicaceae | |
| Arabis gracilipes | Flagstaff rockcress | Brassicaceae | |
| Arabis hirsuta | hairy rockcress | Brassicaceae | |
| Arabis hirsuta var. pycnocarpa | creamflower rockcress | Brassicaceae | |
| Arabis holboellii | Holboell's rockcress | Brassicaceae | |
| Arabis holboellii var. pinetorum | Holboell's rockcress | Brassicaceae | |
| Arabis lignifera | desert rockcress | Brassicaceae | |
| Arabis pendulina | rabbit ear rockcress | Brassicaceae | |
| Arabis pendulina var. pendulina | rabbit ear rockcress | Brassicaceae | |
| Arabis perennans | perennial rockcress | Brassicaceae | |
| Arabis pulchra | beautiful rockcress | Brassicaceae | |
| Arabis pulchra var. gracilis | beautiful rockcress | Brassicaceae | |
| Arabis pulchra var. pallens | beautiful rockcress | Brassicaceae | |
| Arabis sparsiflora | sicklepod rockcress | Brassicaceae | |
| Arabis sparsiflora var. sparsiflora | sicklepod rockcress | Brassicaceae | |
| Arabis tricornuta | Rincon Mountain rockcress | Brassicaceae | |
| Aralia | spikenard | Araliaceae | |
| Aralia humilis | Arizona spikenard | Araliaceae | |
| Aralia racemosa | American spikenard | Araliaceae | |
| Aralia racemosa ssp. bicrenata | American spikenard | Araliaceae | |
| Arbutus | madrone | Ericaceae | |
| Arbutus arizonica | Arizona madrone | Ericaceae | |
| Arceuthobium | dwarf mistletoe | Viscaceae | |
| Arceuthobium abietinum | fir dwarf mistletoe | Viscaceae | |
| Arceuthobium apachecum | Apache dwarf mistletoe | Viscaceae | |
| Arceuthobium blumeri | southwestern white pine dwarf mistletoe | Viscaceae | |
| Arceuthobium divaricatum | pinyon dwarf mistletoe | Viscaceae | |
| Arceuthobium douglasii | Douglas-fir dwarf mistletoe | Viscaceae | |
| Arceuthobium gillii | Huachuca Mountain dwarf mistletoe | Viscaceae | |
| Arceuthobium microcarpum | western spruce dwarf mistletoe | Viscaceae | |
| Arceuthobium vaginatum | pineland dwarf mistletoe | Viscaceae | |
| Arceuthobium vaginatum ssp. cryptopodum | pineland dwarf mistletoe | Viscaceae | |
| Arctium | burdock | Asteraceae | |
| Arctium minus | lesser burdock | Asteraceae | |
| Arctomecon | bearpoppy | Papaveraceae | |
| Arctomecon californica | California bearpoppy | Papaveraceae | |
| Arctostaphylos | manzanita | Ericaceae | |
| Arctostaphylos patula | greenleaf manzanita | Ericaceae | |
| Arctostaphylos pringlei | Pringle manzanita | Ericaceae | |
| Arctostaphylos pringlei ssp. pringlei | Pringle manzanita | Ericaceae | |
| Arctostaphylos pungens | pointleaf manzanita | Ericaceae | |
| Arctostaphylos uva-ursi | kinnikinnick | Ericaceae | |
| Arenaria | sandwort | Caryophyllaceae | |
| Arenaria aberrans | Mt. Dellenbaugh sandwort | Caryophyllaceae | |
| Arenaria aculeata | prickly sandwort | Caryophyllaceae | |
| Arenaria congesta | ballhead sandwort | Caryophyllaceae | |
| Arenaria congesta var. subcongesta | loosehead sandwort | Caryophyllaceae | |
| Arenaria eastwoodiae | Eastwood's sandwort | Caryophyllaceae | |
| Arenaria eastwoodiae var. adenophora | Eastwood's sandwort | Caryophyllaceae | |
| Arenaria eastwoodiae var. eastwoodiae | Eastwood's sandwort | Caryophyllaceae | |
| Arenaria fendleri | Fendler's sandwort | Caryophyllaceae | |
| Arenaria fendleri var. brevifolia | Fendler's sandwort | Caryophyllaceae | |
| Arenaria fendleri var. fendleri | Fendler's sandwort | Caryophyllaceae | |
| Arenaria fendleri var. porteri | Porter's sandwort | Caryophyllaceae | |
| Arenaria fendleri var. tweedyi | Tweedy's sandwort | Caryophyllaceae | |
| Arenaria lanuginosa | spreading sandwort | Caryophyllaceae | |
| Arenaria lanuginosa ssp. saxosa | spreading sandwort | Caryophyllaceae | |
| Arenaria macradenia | Mojave sandwort | Caryophyllaceae | |
| Arenaria macradenia ssp. ferrisiae | Ferris' sandwort | Caryophyllaceae | |
| Arenaria macradenia ssp. macradenia | Mojave sandwort | Caryophyllaceae | |
| Arenaria macradenia ssp. macradenia var. macradenia | Mojave sandwort | Caryophyllaceae | |
| Argemone | pricklypoppy | Papaveraceae | |
| Argemone arizonica | Arizona pricklypoppy | Papaveraceae | |
| Argemone corymbosa | Mojave pricklypoppy | Papaveraceae | |
| Argemone corymbosa ssp. arenicola | Mojave pricklypoppy | Papaveraceae | |
| Argemone corymbosa ssp. corymbosa | Mojave pricklypoppy | Papaveraceae | |
| Argemone gracilenta | Sonoran pricklypoppy | Papaveraceae | |
| Argemone munita | flatbud pricklypoppy | Papaveraceae | |
| Argemone munita ssp. argentea | flatbud pricklypoppy | Papaveraceae | |
| Argemone munita ssp. rotundata | flatbud pricklypoppy | Papaveraceae | |
| Argemone ochroleuca | pale Mexican pricklypoppy | Papaveraceae | |
| Argemone pleiacantha | southwestern pricklypoppy | Papaveraceae | |
| Argemone pleiacantha ssp. ambigua | southwestern pricklypoppy | Papaveraceae | |
| Argemone pleiacantha ssp. pleiacantha | southwestern pricklypoppy | Papaveraceae | |
| Argentina | silverweed | Rosaceae | |
| Argentina anserina | silverweed cinquefoil | Rosaceae | |
| Argyrochosma | false cloak fern | Pteridaceae | |
| Argyrochosma incana | hairy false cloak fern | Pteridaceae | |
| Argyrochosma jonesii | Jones' false cloak fern | Pteridaceae | |
| Argyrochosma limitanea | southwestern false cloak fern | Pteridaceae | |
| Argyrochosma limitanea ssp. limitanea | southwestern false cloak fern | Pteridaceae | |
| Argyrochosma limitanea ssp. mexicana | southwestern false cloak fern | Pteridaceae | |
| Argythamnia | silverbush | Euphorbiaceae | |
| Argythamnia adenophora | glandular silverbush | Euphorbiaceae | |
| Argythamnia brandegeei | Sonoran silverbush | Euphorbiaceae | |
| Argythamnia brandegeei var. intonsa | Sonoran silverbush | Euphorbiaceae | |
| Argythamnia claryana | desert silverbush | Euphorbiaceae | |
| Argythamnia cyanophylla | Charleston Mountain silverbush | Euphorbiaceae | |
| Argythamnia lanceolata | narrowleaf silverbush | Euphorbiaceae | |
| Argythamnia mercurialina | tall silverbush | Euphorbiaceae | |
| Argythamnia mercurialina var. mercurialina | tall silverbush | Euphorbiaceae | |
| Argythamnia neomexicana | New Mexico silverbush | Euphorbiaceae | |
| Argythamnia serrata | Yuma silverbush | Euphorbiaceae | |
| Aristida | threeawn | Poaceae | |
| Aristida adscensionis | sixweeks threeawn | Poaceae | |
| Aristida arizonica | Arizona threeawn | Poaceae | |
| Aristida californica | California threeawn | Poaceae | |
| Aristida californica var. californica | California threeawn | Poaceae | |
| Aristida californica var. glabrata | Santa Rita threeawn | Poaceae | |
| Aristida divaricata | poverty threeawn | Poaceae | |
| Aristida havardii | Havard's threeawn | Poaceae | |
| Aristida longespica | slimspike threeawn | Poaceae | |
| Aristida longespica var. longespica | slimspike threeawn | Poaceae | |
| Aristida oligantha | prairie threeawn | Poaceae | |
| Aristida pansa | Wooton's threeawn | Poaceae | |
| Aristida purpurea | purple threeawn | Poaceae | |
| Aristida purpurea var. fendleriana | Fendler's threeawn | Poaceae | |
| Aristida purpurea var. longiseta | Fendler threeawn | Poaceae | |
| Aristida purpurea var. nealleyi | blue threeawn | Poaceae | |
| Aristida purpurea var. parishii | Parish's threeawn | Poaceae | |
| Aristida purpurea var. perplexa | purple threeawn | Poaceae | |
| Aristida purpurea var. purpurea | purple threeawn | Poaceae | |
| Aristida purpurea var. wrightii | Wright's threeawn | Poaceae | |
| Aristida schiedeana | single threeawn | Poaceae | |
| Aristida schiedeana var. orcuttiana | Orcutt's threeawn | Poaceae | |
| Aristida ternipes | spidergrass | Poaceae | |
| Aristida ternipes var. gentilis | spidergrass | Poaceae | |
| Aristida ternipes var. ternipes | spidergrass | Poaceae | |
| Aristolochia | dutchman's pipe | Aristolochiaceae | |
| Aristolochia watsonii | Watson's dutchman's pipe | Aristolochiaceae | |
| Arnica | arnica | Asteraceae | |
| Arnica chamissonis | Chamisso arnica | Asteraceae | |
| Arnica chamissonis ssp. foliosa | Chamisso arnica | Asteraceae | |
| Arnica chamissonis ssp. foliosa var. andina | Chamisso arnica | Asteraceae | |
| Arnica cordifolia | heartleaf arnica | Asteraceae | |
| Arrhenatherum | oatgrass | Poaceae | |
| Arrhenatherum elatius | tall oatgrass | Poaceae | |
| Arrhenatherum elatius var. elatius | tall oatgrass | Poaceae | |
| Artemisia | sagebrush | Asteraceae | |
| Artemisia annua | sweet sagewort | Asteraceae | |
| Artemisia biennis | biennial wormwood | Asteraceae | |
| Artemisia biennis var. biennis | biennial wormwood | Asteraceae | |
| Artemisia bigelovii | Bigelow sage | Asteraceae | |
| Artemisia campestris | field sagewort | Asteraceae | |
| Artemisia campestris ssp. borealis | field sagewort | Asteraceae | |
| Artemisia campestris ssp. borealis var. scouleriana | field sagewort | Asteraceae | |
| Artemisia campestris ssp. caudata | field sagewort | Asteraceae | |
| Artemisia cana | silver sagebrush | Asteraceae | |
| Artemisia cana ssp. viscidula | silver sagebrush | Asteraceae | |
| Artemisia carruthii | Carruth's sagewort | Asteraceae | |
| Artemisia dracunculus | tarragon | Asteraceae | |
| Artemisia filifolia | sand sagebrush | Asteraceae | |
| Artemisia franserioides | ragweed sagebrush | Asteraceae | |
| Artemisia frigida | prairie sagewort | Asteraceae | |
| Artemisia lindleyana | Columbia River wormwood | Asteraceae | |
| Artemisia ludoviciana | white sagebrush | Asteraceae | |
| Artemisia ludoviciana ssp. albula | white sagebrush | Asteraceae | |
| Artemisia ludoviciana ssp. ludoviciana | white sagebrush | Asteraceae | |
| Artemisia ludoviciana ssp. mexicana | white sagebrush | Asteraceae | |
| Artemisia ludoviciana ssp. redolens | white sagebrush | Asteraceae | |
| Artemisia ludoviciana ssp. sulcata | white sagebrush | Asteraceae | |
| Artemisia nova | black sagebrush | Asteraceae | |
| Artemisia pygmaea | pygmy sagebrush | Asteraceae | |
| Artemisia tridentata | big sagebrush | Asteraceae | |
| Artemisia tridentata ssp. tridentata | basin big sagebrush | Asteraceae | |
| Artemisia tridentata ssp. wyomingensis | Wyoming big sagebrush | Asteraceae | |
| Arundo | giant reed | Poaceae | |
| Arundo donax | giant reed | Poaceae | |
| Asanthus | brickellbush | Asteraceae | |
| Asanthus squamulosus | Mule Mountain brickellbush | Asteraceae | |
| Asclepias | milkweed | Asclepiadaceae | |
| Asclepias albicans | whitestem milkweed | Asclepiadaceae | |
| Asclepias angustifolia | Arizona milkweed | Asclepiadaceae | |
| Asclepias asperula | spider milkweed | Asclepiadaceae | |
| Asclepias asperula ssp. asperula | spider milkweed | Asclepiadaceae | |
| Asclepias asperula ssp. capricornu | antelopehorns | Asclepiadaceae | |
| Asclepias brachystephana | bract milkweed | Asclepiadaceae | |
| Asclepias cryptoceras | pallid milkweed | Asclepiadaceae | |
| Asclepias cryptoceras ssp. cryptoceras | pallid milkweed | Asclepiadaceae | |
| Asclepias cutleri | Cutler's milkweed | Asclepiadaceae | |
| Asclepias engelmanniana | Engelmann's milkweed | Asclepiadaceae | |
| Asclepias erosa | desert milkweed | Asclepiadaceae | |
| Asclepias glaucescens | nodding milkweed | Asclepiadaceae | |
| Asclepias hallii | Hall's milkweed | Asclepiadaceae | |
| Asclepias hypoleuca | mahogany milkweed | Asclepiadaceae | |
| Asclepias involucrata | dwarf milkweed | Asclepiadaceae | |
| Asclepias latifolia | broadleaf milkweed | Asclepiadaceae | |
| Asclepias lemmonii | Lemmon's milkweed | Asclepiadaceae | |
| Asclepias linaria | pineneedle milkweed | Asclepiadaceae | |
| Asclepias macrotis | longhood milkweed | Asclepiadaceae | |
| Asclepias nummularia | tufted milkweed | Asclepiadaceae | |
| Asclepias nyctaginifolia | Mojave milkweed | Asclepiadaceae | |
| Asclepias quinquedentata | slimpod milkweed | Asclepiadaceae | |
| Asclepias rusbyi | Rusby's milkweed | Asclepiadaceae | |
| Asclepias speciosa | showy milkweed | Asclepiadaceae | |
| Asclepias subulata | rush milkweed | Asclepiadaceae | |
| Asclepias subverticillata | horsetail milkweed | Asclepiadaceae | |
| Asclepias tuberosa | butterfly milkweed | Asclepiadaceae | |
| Asclepias tuberosa ssp. interior | butterfly milkweed | Asclepiadaceae | |
| Asclepias uncialis | wheel milkweed | Asclepiadaceae | |
| Asclepias uncialis ssp. ruthiae | Ruth's milkweed | Asclepiadaceae | |
| Asclepias uncialis ssp. uncialis | wheel milkweed | Asclepiadaceae | |
| Asclepias verticillata | whorled milkweed | Asclepiadaceae | |
| Asclepias viridiflora | green comet milkweed | Asclepiadaceae | |
| Asclepias welshii | Welsh's milkweed | Asclepiadaceae | |
| Asparagus | asparagus | Liliaceae | |
| Asparagus officinalis | garden asparagus | Liliaceae | |
| Aspicarpa | asphead | Malpighiaceae | |
| Aspicarpa hirtella | chaparral asphead | Malpighiaceae | |
| Asplenium | spleenwort | Aspleniaceae | |
| Asplenium adiantum-nigrum | black spleenwort | Aspleniaceae | |
| Asplenium dalhousiae | Countess Dalhousie's spleenwort | Aspleniaceae | |
| Asplenium exiguum | little spleenwort | Aspleniaceae | |
| Asplenium monanthes | singlesorus spleenwort | Aspleniaceae | |
| Asplenium palmeri | Palmer's spleenwort | Aspleniaceae | |
| Asplenium platyneuron | ebony spleenwort | Aspleniaceae | |
| Asplenium platyneuron var. platyneuron | ebony spleenwort | Aspleniaceae | |
| Asplenium resiliens | blackstem spleenwort | Aspleniaceae | |
| Asplenium septentrionale | forked spleenwort | Aspleniaceae | |
| Asplenium trichomanes | maidenhair spleenwort | Aspleniaceae | |
| Asplenium trichomanes ssp. trichomanes | maidenhair spleenwort | Aspleniaceae | |
| Astragalus | milkvetch | Fabaceae | |
| Astragalus acutirostris | sharpkeel milkvetch | Fabaceae | |
| Astragalus albulus | cibola milkvetch | Fabaceae | |
| Astragalus allochrous | halfmoon milkvetch | Fabaceae | |
| Astragalus allochrous var. allochrous | halfmoon milkvetch | Fabaceae | |
| Astragalus allochrous var. playanus | halfmoon milkvetch | Fabaceae | |
| Astragalus amphioxys | Crescent milkvetch | Fabaceae | |
| Astragalus amphioxys var. amphioxys | Crescent milkvetch | Fabaceae | |
| Astragalus amphioxys var. modestus | Crescent milkvetch | Fabaceae | |
| Astragalus amphioxys var. musimonum | Crescent milkvetch | Fabaceae | |
| Astragalus amphioxys var. vespertinus | Aladdin's slippers | Fabaceae | |
| Astragalus ampullarius | gumbo milkvetch | Fabaceae | |
| Astragalus argophyllus | silverleaf milkvetch | Fabaceae | |
| Astragalus argophyllus var. martinii | silverleaf milkvetch | Fabaceae | |
| Astragalus argophyllus var. panguicensis | silverleaf milkvetch | Fabaceae | |
| Astragalus argophyllus var. stocksii | silverleaf milkvetch | Fabaceae | |
| Astragalus aridus | annual desert milkvetch | Fabaceae | |
| Astragalus arizonicus | Arizona milkvetch | Fabaceae | |
| Astragalus beathii | Beath's milkvetch | Fabaceae | |
| Astragalus bisulcatus | twogrooved milkvetch | Fabaceae | |
| Astragalus bisulcatus var. bisulcatus | twogrooved milkvetch | Fabaceae | |
| Astragalus bisulcatus var. haydenianus | Hayden's milkvetch | Fabaceae | |
| Astragalus bisulcatus var. major | twogrooved milkvetch | Fabaceae | |
| Astragalus brandegeei | Brandegee's milkvetch | Fabaceae | |
| Astragalus calycosus | Torrey's milkvetch | Fabaceae | |
| Astragalus calycosus var. calycosus | Torrey's milkvetch | Fabaceae | |
| Astragalus calycosus var. scaposus | Torrey's milkvetch | Fabaceae | |
| Astragalus castaneiformis | chestnut milkvetch | Fabaceae | |
| Astragalus ceramicus | painted milkvetch | Fabaceae | |
| Astragalus ceramicus var. ceramicus | painted milkvetch | Fabaceae | |
| Astragalus chuskanus | San Juan milkvetch | Fabaceae | |
| Astragalus cobrensis | copper mine milkvetch | Fabaceae | |
| Astragalus cobrensis var. cobrensis | copper mine milkvetch | Fabaceae | |
| Astragalus cobrensis var. maguirei | Maguire's milkvetch | Fabaceae | |
| Astragalus coccineus | scarlet milkvetch | Fabaceae | |
| Astragalus coltonii | Colton's milkvetch | Fabaceae | |
| Astragalus coltonii var. moabensis | Moab milkvetch | Fabaceae | |
| Astragalus crassicarpus | groundplum milkvetch | Fabaceae | |
| Astragalus crassicarpus var. cavus | groundplum milkvetch | Fabaceae | |
| Astragalus cremnophylax | sentry milkvetch | Fabaceae | |
| Astragalus cremnophylax var. cremnophylax | sentry milkvetch | Fabaceae | |
| Astragalus cremnophylax var. hevronii | sentry milkvetch | Fabaceae | |
| Astragalus cremnophylax var. myriorrhaphis | sentry milkvetch | Fabaceae | |
| Astragalus crotalariae | Salton milkvetch | Fabaceae | |
| Astragalus desperatus | rimrock milkvetch | Fabaceae | |
| Astragalus desperatus var. conspectus | rimrock milkvetch | Fabaceae | |
| Astragalus desperatus var. desperatus | rimrock milkvetch | Fabaceae | |
| Astragalus didymocarpus | dwarf white milkvetch | Fabaceae | |
| Astragalus didymocarpus var. dispermus | dwarf white milkvetch | Fabaceae | |
| Astragalus egglestonii | Eggleston's milkvetch | Fabaceae | |
| Astragalus emoryanus | Emory's milkvetch | Fabaceae | |
| Astragalus emoryanus var. emoryanus | Emory's milkvetch | Fabaceae | |
| Astragalus endopterus | sandbar milkvetch | Fabaceae | |
| Astragalus ensiformis | pagumpa milkvetch | Fabaceae | |
| Astragalus ensiformis var. ensiformis | pagumpa milkvetch | Fabaceae | |
| Astragalus episcopus | bishop's milkvetch | Fabaceae | |
| Astragalus episcopus var. episcopus | bishop's milkvetch | Fabaceae | |
| Astragalus episcopus var. lancearius | bishop's milkvetch | Fabaceae | |
| Astragalus eremiticus | hermit milkvetch | Fabaceae | |
| Astragalus eurylobus | Needle Mountain milkvetch | Fabaceae | |
| Astragalus flavus | yellow milkvetch | Fabaceae | |
| Astragalus flexuosus | flexile milkvetch | Fabaceae | |
| Astragalus flexuosus var. diehlii | Diehl's milkvetch | Fabaceae | |
| Astragalus flexuosus var. greenei | Greene's milkvetch | Fabaceae | |
| Astragalus fucatus | Hopi milkvetch | Fabaceae | |
| Astragalus geyeri | Geyer's milkvetch | Fabaceae | |
| Astragalus geyeri var. triquetrus | Geyer's milkvetch | Fabaceae | |
| Astragalus gilensis | Gila milkvetch | Fabaceae | |
| Astragalus hallii | Hall's milkvetch | Fabaceae | |
| Astragalus hallii var. fallax | Hall's milkvetch | Fabaceae | |
| Astragalus hartwegii | Hartweg's milkvetch | Fabaceae | |
| Astragalus holmgreniorum | Paradox milkvetch | Fabaceae | |
| Astragalus humistratus | groundcover milkvetch | Fabaceae | |
| Astragalus humistratus var. crispulus | groundcover milkvetch | Fabaceae | |
| Astragalus humistratus var. hosackiae | groundcover milkvetch | Fabaceae | |
| Astragalus humistratus var. humistratus | groundcover milkvetch | Fabaceae | |
| Astragalus humistratus var. humivagans | groundcover milkvetch | Fabaceae | |
| Astragalus humistratus var. sonorae | groundcover milkvetch | Fabaceae | |
| Astragalus humistratus var. tenerrimus | groundcover milkvetch | Fabaceae | |
| Astragalus hypoxylus | Huachuca Mountain milkvetch | Fabaceae | |
| Astragalus insularis | Cedros milkvetch | Fabaceae | |
| Astragalus insularis var. harwoodii | Harwood's milkvetch | Fabaceae | |
| Astragalus kentrophyta | spiny milkvetch | Fabaceae | |
| Astragalus kentrophyta var. coloradoensis | Colorado spiny milkvetch | Fabaceae | |
| Astragalus kentrophyta var. elatus | tall spiny milkvetch | Fabaceae | |
| Astragalus layneae | widow's milkvetch | Fabaceae | |
| Astragalus lentiginosus | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. ambiguus | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. australis | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. borreganus | Borrego milkvetch | Fabaceae | |
| Astragalus lentiginosus var. diphysus | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. maricopae | Maricopa milkvetch | Fabaceae | |
| Astragalus lentiginosus var. oropedii | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. palans | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. stramineus | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. trumbullensis | Fabaceae | ||
| Astragalus lentiginosus var. vitreus | freckled milkvetch | Fabaceae | |
| Astragalus lentiginosus var. wilsonii | Wilson's milkvetch | Fabaceae | |
| Astragalus lentiginosus var. yuccanus | yucca milkvetch | Fabaceae | |
| Astragalus lonchocarpus | rushy milkvetch | Fabaceae | |
| Astragalus magdalenae | satiny milkvetch | Fabaceae | |
| Astragalus magdalenae var. peirsonii | Peirson's milkvetch | Fabaceae | |
| Astragalus miser | timber milkvetch | Fabaceae | |
| Astragalus miser var. oblongifolius | timber milkvetch | Fabaceae | |
| Astragalus moencoppensis | Moenkopi milkvetch | Fabaceae | |
| Astragalus mokiacensis | Mokiak milkvetch | Fabaceae | |
| Astragalus mollissimus | woolly locoweed | Fabaceae | |
| Astragalus mollissimus var. bigelovii | woolly locoweed | Fabaceae | |
| Astragalus mollissimus var. mogollonicus | woolly locoweed | Fabaceae | |
| Astragalus mollissimus var. thompsoniae | woolly locoweed | Fabaceae | |
| Astragalus monumentalis | Monument Valley milkvetch | Fabaceae | |
| Astragalus monumentalis var. cottamii | Cottam's milkvetch | Fabaceae | |
| Astragalus monumentalis var. monumentalis | Monument Valley milkvetch | Fabaceae | |
| Astragalus newberryi | Newberry's milkvetch | Fabaceae | |
| Astragalus newberryi var. aquarii | Newberry's milkvetch | Fabaceae | |
| Astragalus newberryi var. blyae | Newberry's milkvetch | Fabaceae | |
| Astragalus newberryi var. castoreus | Newberry's milkvetch | Fabaceae | |
| Astragalus newberryi var. newberryi | Newberry's milkvetch | Fabaceae | |
| Astragalus nothoxys | sheep milkvetch | Fabaceae | |
| Astragalus nutriosensis | Apache milkvetch | Fabaceae | |
| Astragalus nuttallianus | smallflowered milkvetch | Fabaceae | |
| Astragalus nuttallianus var. austrinus | smallflowered milkvetch | Fabaceae | |
| Astragalus nuttallianus var. cedrosensis | turkeypeas | Fabaceae | |
| Astragalus nuttallianus var. imperfectus | turkeypeas | Fabaceae | |
| Astragalus nuttallianus var. micranthiformis | turkeypeas | Fabaceae | |
| Astragalus oophorus | egg milkvetch | Fabaceae | |
| Astragalus oophorus var. caulescens | egg milkvetch | Fabaceae | |
| Astragalus palmeri | Palmer's milkvetch | Fabaceae | |
| Astragalus pattersonii | Patterson's milkvetch | Fabaceae | |
| Astragalus pinonis | pinyon milkvetch | Fabaceae | |
| Astragalus pinonis var. atwoodii | Duane's milkvetch | Fabaceae | |
| Astragalus praelongus | stinking milkvetch | Fabaceae | |
| Astragalus praelongus var. lonchopus | stinking milkvetch | Fabaceae | |
| Astragalus praelongus var. praelongus | stinking milkvetch | Fabaceae | |
| Astragalus preussii | Preuss' milkvetch | Fabaceae | |
| Astragalus preussii var. laxiflorus | Preuss' milkvetch | Fabaceae | |
| Astragalus preussii var. preussii | Preuss' milkvetch | Fabaceae | |
| Astragalus recurvus | recurved milkvetch | Fabaceae | |
| Astragalus rusbyi | Rusby's milkvetch | Fabaceae | |
| Astragalus sabulonum | gravel milkvetch | Fabaceae | |
| Astragalus scopulorum | Rocky Mountain milkvetch | Fabaceae | |
| Astragalus sesquiflorus | sandstone milkvetch | Fabaceae | |
| Astragalus sophoroides | painted desert milkvetch | Fabaceae | |
| Astragalus straturensis | Pine Valley milkvetch | Fabaceae | |
| Astragalus striatiflorus | escarpment milkvetch | Fabaceae | |
| Astragalus subcinereus | Silver's milkvetch | Fabaceae | |
| Astragalus tephrodes | ashen milkvetch | Fabaceae | |
| Astragalus tephrodes var. brachylobus | ashen milkvetch | Fabaceae | |
| Astragalus tephrodes var. chloridae | ashen milkvetch | Fabaceae | |
| Astragalus tephrodes var. tephrodes | ashen milkvetch | Fabaceae | |
| Astragalus tetrapterus | fourwing milkvetch | Fabaceae | |
| Astragalus thurberi | Thurber's milkvetch | Fabaceae | |
| Astragalus titanophilus | limestone milkvetch | Fabaceae | |
| Astragalus toanus | Toano milkvetch | Fabaceae | |
| Astragalus toanus var. scidulus | Toano milkvetch | Fabaceae | |
| Astragalus troglodytus | creeping milkvetch | Fabaceae | |
| Astragalus vaccarum | Cow Spring milkvetch | Fabaceae | |
| Astragalus wingatanus | Fort Wingate milkvetch | Fabaceae | |
| Astragalus xiphoides | gladiator milkvetch | Fabaceae | |
| Astragalus zionis | Zion milkvetch | Fabaceae | |
| Astragalus zionis var. zionis | Zion milkvetch | Fabaceae | |
| Astrolepis | cloakfern | Pteridaceae | |
| Astrolepis cochisensis | Cochise scaly cloakfern | Pteridaceae | |
| Astrolepis cochisensis ssp. arizonica | Arizona scaly cloakfern | Pteridaceae | |
| Astrolepis cochisensis ssp. cochisensis | Cochise scaly cloakfern | Pteridaceae | |
| Astrolepis integerrima | hybrid cloakfern | Pteridaceae | |
| Astrolepis sinuata | wavy scaly cloakfern | Pteridaceae | |
| Astrolepis sinuata ssp. sinuata | wavy scaly cloakfern | Pteridaceae | |
| Astrolepis windhamii | Windham's scaly cloakfern | Pteridaceae | |
| Atamisquea | atamisquea | Capparaceae | |
| Atamisquea emarginata | vomitbush | Capparaceae | |
| Athyrium | ladyfern | Dryopteridaceae | |
| Athyrium filix-femina | common ladyfern | Dryopteridaceae | |
| Athyrium filix-femina ssp. cyclosorum | subarctic ladyfern | Dryopteridaceae | |
| Athysanus | sandweed | Brassicaceae | |
| Athysanus pusillus | common sandweed | Brassicaceae | |
| Atrichoseris | atrichoseris | Asteraceae | |
| Atrichoseris platyphylla | parachute plant | Asteraceae | |
| Atriplex | saltbush | Chenopodiaceae | |
| Atriplex acanthocarpa | tubercled saltbush | Chenopodiaceae | |
| Atriplex acanthocarpa ssp. acanthocarpa | tubercled saltbush | Chenopodiaceae | |
| Atriplex argentea | silverscale saltbush | Chenopodiaceae | |
| Atriplex argentea ssp. argentea | silverscale saltbush | Chenopodiaceae | |
| Atriplex argentea ssp. argentea var. argentea | silverscale saltbush | Chenopodiaceae | |
| Atriplex argentea ssp. argentea var. caput-medusae | stalked saltbush | Chenopodiaceae | |
| Atriplex argentea ssp. expansa | silverscale saltbush | Chenopodiaceae | |
| Atriplex asterocarpa | Chinle saltbush | Chenopodiaceae | |
| Atriplex canescens | fourwing saltbush | Chenopodiaceae | |
| Atriplex canescens var. angustifolia | fourwing saltbush | Chenopodiaceae | |
| Atriplex canescens var. canescens | fourwing saltbush | Chenopodiaceae | |
| Atriplex canescens var. linearis | thinleaf fourwing saltbush | Chenopodiaceae | |
| Atriplex confertifolia | shadscale saltbush | Chenopodiaceae | |
| Atriplex cuneata | valley saltbush | Chenopodiaceae | |
| Atriplex cuneata ssp. cuneata | valley saltbush | Chenopodiaceae | |
| Atriplex elegans | wheelscale saltbush | Chenopodiaceae | |
| Atriplex elegans var. elegans | wheelscale saltbush | Chenopodiaceae | |
| Atriplex elegans var. fasciculata | wheelscale saltbush | Chenopodiaceae | |
| Atriplex elegans var. thornberi | wheelscale saltbush | Chenopodiaceae | |
| Atriplex garrettii | Garrett's saltbush | Chenopodiaceae | |
| Atriplex griffithsii | Griffiths' saltbush | Chenopodiaceae | |
| Atriplex hymenelytra | desertholly | Chenopodiaceae | |
| Atriplex lentiformis | big saltbush | Chenopodiaceae | |
| Atriplex lentiformis ssp. lentiformis | big saltbush | Chenopodiaceae | |
| Atriplex navajoensis | Navajo saltbush | Chenopodiaceae | |
| Atriplex obovata | mound saltbush | Chenopodiaceae | |
| Atriplex pacifica | Davidson's saltbush | Chenopodiaceae | |
| Atriplex phyllostegia | leafcover saltweed | Chenopodiaceae | |
| Atriplex polycarpa | cattle saltbush | Chenopodiaceae | |
| Atriplex powellii | Powell's saltweed | Chenopodiaceae | |
| Atriplex prostrata | triangle orache | Chenopodiaceae | |
| Atriplex rosea | tumbling saltweed | Chenopodiaceae | |
| Atriplex saccaria | sack saltbush | Chenopodiaceae | |
| Atriplex semibaccata | Australian saltbush | Chenopodiaceae | |
| Atriplex serenana | bractscale | Chenopodiaceae | |
| Atriplex serenana var. serenana | bractscale | Chenopodiaceae | |
| Atriplex subspicata | saline saltbush | Chenopodiaceae | |
| Atriplex torreyi | Torrey's saltbush | Chenopodiaceae | |
| Atriplex wrightii | Wright's saltbush | Chenopodiaceae | |
| Avena | oat | Poaceae | |
| Avena barbata | slender oat | Poaceae | |
| Avena fatua | wild oat | Poaceae | |
| Avena sativa | common oat | Poaceae | |
| Ayenia | ayenia | Sterculiaceae | |
| Ayenia ardua | wingstem ayenia | Sterculiaceae | |
| Ayenia compacta | California ayenia | Sterculiaceae | |
| Ayenia filiformis | Trans-Pecos ayenia | Sterculiaceae | |
| Ayenia glabra | smooth ayenia | Sterculiaceae | |
| Ayenia insulicola | dwarf ayenia | Sterculiaceae | |
| Ayenia microphylla | dense ayenia | Sterculiaceae | |
| Azolla | mosquitofern | Azollaceae | |
| Azolla filiculoides | Pacific mosquitofern | Azollaceae | |
| Azolla mexicana | Mexican mosquitofern | Azollaceae | |
| B | |||
| Baccharis | baccharis | Asteraceae | |
| Baccharis bigelovii | Bigelow's false willow | Asteraceae | |
| Baccharis brachyphylla | shortleaf baccharis | Asteraceae | |
| Baccharis emoryi | Emory's baccharis | Asteraceae | |
| Baccharis neglecta | Rooseveltweed | Asteraceae | |
| Baccharis pteronioides | yerba de pasmo | Asteraceae | |
| Baccharis salicifolia | mule-fat | Asteraceae | |
| Baccharis sarothroides | desertbroom | Asteraceae | |
| Baccharis sergiloides | desert baccharis | Asteraceae | |
| Baccharis thesioides | Arizona baccharis | Asteraceae | |
| Baccharis wrightii | Wright's baccharis | Asteraceae | |
| Bacopa | waterhyssop | Scrophulariaceae | |
| Bacopa monnieri | herb of grace | Scrophulariaceae | |
| Bacopa rotundifolia | disk waterhyssop | Scrophulariaceae | |
| Bahia | bahia | Asteraceae | |
| Bahia absinthifolia | hairyseed bahia | Asteraceae | |
| Bahia absinthifolia var. absinthifolia | hairyseed bahia | Asteraceae | |
| Bahia absinthifolia var. dealbata | Dealbata's bahia | Asteraceae | |
| Bahia biternata | slimlobe bahia | Asteraceae | |
| Bahia dissecta | ragleaf bahia | Asteraceae | |
| Baileya | desert marigold | Asteraceae | |
| Baileya multiradiata | desert marigold | Asteraceae | |
| Baileya pauciradiata | laxflower | Asteraceae | |
| Baileya pleniradiata | woolly desert marigold | Asteraceae | |
| Balsamorhiza | balsamroot | Asteraceae | |
| Balsamorhiza hookeri | Hooker's balsamroot | Asteraceae | |
| Balsamorhiza hookeri var. hispidula | hairy balsamroot | Asteraceae | |
| Balsamorhiza sagittata | arrowleaf balsamroot | Asteraceae | |
| Barbarea | yellowrocket | Brassicaceae | |
| Barbarea orthoceras | American yellowrocket | Brassicaceae | |
| Barkleyanthus | willow ragwort | Asteraceae | |
| Barkleyanthus salicifolius | willow ragwort | Asteraceae | |
| Bassia | smotherweed | Chenopodiaceae | |
| Bassia americana | green molly | Chenopodiaceae | |
| Bassia hyssopifolia | fivehorn smotherweed | Chenopodiaceae | |
| Bassia prostrata | forage kochia | Chenopodiaceae | |
| Bassia scoparia | burningbush | Chenopodiaceae | |
| Bebbia | sweetbush | Asteraceae | |
| Bebbia juncea | sweetbush | Asteraceae | |
| Bebbia juncea var. aspera | sweetbush | Asteraceae | |
| Beckmannia | sloughgrass | Poaceae | |
| Beckmannia syzigachne | American sloughgrass | Poaceae | |
| Berberis | barberry | Berberidaceae | |
| Berberis harrisoniana | Harrison's barberry | Berberidaceae | |
| Berberis wilcoxii | Wilcox's barberry | Berberidaceae | |
| Berlandiera | greeneyes | Asteraceae | |
| Berlandiera lyrata | lyreleaf greeneyes | Asteraceae | |
| Bernardia | myrtlecroton | Euphorbiaceae | |
| Bernardia myricifolia | mouse's eye | Euphorbiaceae | |
| Berula | waterparsnip | Apiaceae | |
| Berula erecta | cutleaf waterparsnip | Apiaceae | |
| Besseya | kittentail | Scrophulariaceae | |
| Besseya arizonica | Arizona coraldrops | Scrophulariaceae | |
| Besseya plantaginea | White River coraldrops | Scrophulariaceae | |
| Betula | birch | Betulaceae | |
| Betula occidentalis | water birch | Betulaceae | |
| Bidens | beggarticks | Asteraceae | |
| Bidens aurea | Arizona beggarticks | Asteraceae | |
| Bidens bigelovii | Bigelow's beggarticks | Asteraceae | |
| Bidens bigelovii var. angustiloba | Asteraceae | ||
| Bidens bigelovii var. bigelovii | Bigelow's beggarticks | Asteraceae | |
| Bidens bipinnata | Spanish needles | Asteraceae | |
| Bidens cernua | nodding beggartick | Asteraceae | |
| Bidens ferulifolia | Apache beggarticks | Asteraceae | |
| Bidens frondosa | devil's beggartick | Asteraceae | |
| Bidens heterosperma | Rocky Mountain beggarticks | Asteraceae | |
| Bidens laevis | smooth beggartick | Asteraceae | |
| Bidens lemmonii | Lemmon's beggarticks | Asteraceae | |
| Bidens leptocephala | fewflower beggarticks | Asteraceae | |
| Bidens pilosa | hairy beggarticks | Asteraceae | |
| Bidens tenuisecta | slimlobe beggarticks | Asteraceae | |
| Blepharoneuron | dropseed | Poaceae | |
| Blepharoneuron tricholepis | pine dropseed | Poaceae | |
| Boehmeria | false nettle | Urticaceae | |
| Boehmeria cylindrica | smallspike false nettle | Urticaceae | |
| Boerhavia | spiderling | Nyctaginaceae | |
| Boerhavia coccinea | scarlet spiderling | Nyctaginaceae | |
| Boerhavia coulteri | Coulter's spiderling | Nyctaginaceae | |
| Boerhavia erecta | erect spiderling | Nyctaginaceae | |
| Boerhavia gracillima | slimstalk spiderling | Nyctaginaceae | |
| Boerhavia intermedia | fivewing spiderling | Nyctaginaceae | |
| Boerhavia megaptera | Tucson Mountain spiderling | Nyctaginaceae | |
| Boerhavia pterocarpa | Apache Pass spiderling | Nyctaginaceae | |
| Boerhavia purpurascens | purple spiderling | Nyctaginaceae | |
| Boerhavia scandens | climbing wartclub | Nyctaginaceae | |
| Boerhavia spicata | creeping spiderling | Nyctaginaceae | |
| Boerhavia triquetra | slender spiderling | Nyctaginaceae | |
| Boerhavia wrightii | largebract spiderling | Nyctaginaceae | |
| Bommeria | bommeria fern | Pteridaceae | |
| Bommeria hispida | copper fern | Pteridaceae | |
| Bothriochloa | beardgrass | Poaceae | |
| Bothriochloa barbinodis | cane bluestem | Poaceae | |
| Bothriochloa ischaemum | yellow bluestem | Poaceae | |
| Bothriochloa ischaemum var. songarica | yellow bluestem | Poaceae | |
| Bothriochloa laguroides | silver beardgrass | Poaceae | |
| Bothriochloa laguroides ssp. torreyana | silver beardgrass | Poaceae | |
| Bothriochloa springfieldii | Springfield's beardgrass | Poaceae | |
| Bothriochloa wrightii | Wright's beardgrass | Poaceae | |
| Botrychium | grapefern | Ophioglossaceae | |
| Botrychium crenulatum | scalloped moonwort | Ophioglossaceae | |
| Botrychium echo | reflected grapefern | Ophioglossaceae | |
| Botrychium hesperium | western moonwort | Ophioglossaceae | |
| Botrychium lanceolatum | lanceleaf grapefern | Ophioglossaceae | |
| Botrychium lanceolatum var. lanceolatum | lanceleaf grapefern | Ophioglossaceae | |
| Botrychium lunaria | common moonwort | Ophioglossaceae | |
| Botrychium minganense | Mingan moonwort | Ophioglossaceae | |
| Botrychium multifidum | leathery grapefern | Ophioglossaceae | |
| Botrychium pinnatum | northern moonwort | Ophioglossaceae | |
| Botrychium virginianum | rattlesnake fern | Ophioglossaceae | |
| Bouchea | bouchea | Verbenaceae | |
| Bouchea prismatica | prism bouchea | Verbenaceae | |
| Bouteloua | grama | Poaceae | |
| Bouteloua aristidoides | needle grama | Poaceae | |
| Bouteloua aristidoides var. aristidoides | needle grama | Poaceae | |
| Bouteloua aristidoides var. arizonica | Arizona needle grama | Poaceae | |
| Bouteloua barbata | sixweeks grama | Poaceae | |
| Bouteloua chondrosioides | sprucetop grama | Poaceae | |
| Bouteloua curtipendula | sideoats grama | Poaceae | |
| Bouteloua curtipendula var. caespitosa | sideoats grama | Poaceae | |
| Bouteloua curtipendula var. curtipendula | sideoats grama | Poaceae | |
| Bouteloua dactyloides | buffalograss | Poaceae | |
| Bouteloua diversispicula | zacale | Poaceae | |
| Bouteloua eludens | Santa Rita Mountain grama | Poaceae | |
| Bouteloua eriopoda | black grama | Poaceae | |
| Bouteloua gracilis | blue grama | Poaceae | |
| Bouteloua hirsuta | hairy grama | Poaceae | |
| Bouteloua hirsuta var. hirsuta | hairy grama | Poaceae | |
| Bouteloua parryi | Parry's grama | Poaceae | |
| Bouteloua radicosa | purple grama | Poaceae | |
| Bouteloua repens | slender grama | Poaceae | |
| Bouteloua rothrockii | Rothrock's grama | Poaceae | |
| Bouteloua simplex | matted grama | Poaceae | |
| Bouteloua trifida | red grama | Poaceae | |
| Bouteloua trifida var. trifida | red grama | Poaceae | |
| Bouvardia | bouvardia | Rubiaceae | |
| Bouvardia ternifolia | firecrackerbush | Rubiaceae | |
| Bowlesia | bowlesia | Apiaceae | |
| Bowlesia incana | hoary bowlesia | Apiaceae | |
| Brachystigma | desert foxglove | Scrophulariaceae | |
| Brachystigma wrightii | Arizona desert foxglove | Scrophulariaceae | |
| Brandegea | starvine | Cucurbitaceae | |
| Brandegea bigelovii | desert starvine | Cucurbitaceae | |
| Brassica | mustard | Brassicaceae | |
| Brassica juncea | India mustard | Brassicaceae | |
| Brassica nigra | black mustard | Brassicaceae | |
| Brassica rapa | field mustard | Brassicaceae | |
| Brassica rapa var. rapa | field mustard | Brassicaceae | |
| Brassica tournefortii | Asian mustard | Brassicaceae | |
| Brickellia | brickellbush | Asteraceae | |
| Brickellia amplexicaulis | earleaf brickellbush | Asteraceae | |
| Brickellia amplexicaulis var. amplexicaulis | earleaf brickellbush | Asteraceae | |
| Brickellia amplexicaulis var. lanceolata | earleaf brickellbush | Asteraceae | |
| Brickellia atractyloides | spearleaf brickellbush | Asteraceae | |
| Brickellia baccharidea | resinleaf brickellbush | Asteraceae | |
| Brickellia betonicifolia | betonyleaf brickellbush | Asteraceae | |
| Brickellia brachyphylla | plumed brickellbush | Asteraceae | |
| Brickellia californica | California brickellbush | Asteraceae | |
| Brickellia californica var. californica | California brickellbush | Asteraceae | |
| Brickellia coulteri | Coulter's brickellbush | Asteraceae | |
| Brickellia desertorum | desert brickellbush | Asteraceae | |
| Brickellia eupatorioides | false boneset | Asteraceae | |
| Brickellia eupatorioides var. chlorolepis | false boneset | Asteraceae | |
| Brickellia floribunda | Chihuahuan brickellbush | Asteraceae | |
| Brickellia frutescens | shrubby brickellbush | Asteraceae | |
| Brickellia grandiflora | tasselflower brickellbush | Asteraceae | |
| Brickellia incana | woolly brickellbush | Asteraceae | |
| Brickellia lemmonii | Lemmon's brickellbush | Asteraceae | |
| Brickellia lemmonii var. lemmonii | Lemmon's brickellbush | Asteraceae | |
| Brickellia longifolia | longleaf brickellbush | Asteraceae | |
| Brickellia longifolia var. longifolia | longleaf brickellbush | Asteraceae | |
| Brickellia microphylla | littleleaf brickellbush | Asteraceae | |
| Brickellia microphylla var. scabra | rough brickellbush | Asteraceae | |
| Brickellia microphylla var. watsonii | Watson's brickellbush | Asteraceae | |
| Brickellia oblongifolia | Mojave brickellbush | Asteraceae | |
| Brickellia oblongifolia var. linifolia | narrowleaf brickellbush | Asteraceae | |
| Brickellia parvula | Mt. Davis brickellbush | Asteraceae | |
| Brickellia pringlei | Pringle's brickellbush | Asteraceae | |
| Brickellia rusbyi | stinking brickellbush | Asteraceae | |
| Brickellia simplex | Sonoran brickellbush | Asteraceae | |
| Brickellia venosa | veiny brickellbush | Asteraceae | |
| Brickelliastrum | brickellbush | Asteraceae | |
| Brickelliastrum fendleri | Fendler's brickellbush | Asteraceae | |
| Bromus | brome | Poaceae | |
| Bromus arenarius | Australian brome | Poaceae | |
| Bromus arizonicus | Arizona brome | Poaceae | |
| Bromus arvensis | field brome | Poaceae | |
| Bromus berteroanus | Chilean chess | Poaceae | |
| Bromus catharticus | rescuegrass | Poaceae | |
| Bromus ciliatus | fringed brome | Poaceae | |
| Bromus ciliatus var. ciliatus | fringed brome | Poaceae | |
| Bromus ciliatus var. richardsonii | fringed brome | Poaceae | |
| Bromus diandrus | ripgut brome | Poaceae | |
| Bromus diandrus ssp. rigidus | ripgut brome | Poaceae | |
| Bromus frondosus | weeping brome | Poaceae | |
| Bromus hordeaceus | soft brome | Poaceae | |
| Bromus hordeaceus ssp. hordeaceus | soft brome | Poaceae | |
| Bromus inermis | smooth brome | Poaceae | |
| Bromus inermis ssp. inermis | smooth brome | Poaceae | |
| Bromus inermis ssp. inermis var. inermis | smooth brome | Poaceae | |
| Bromus lanatipes | woolly brome | Poaceae | |
| Bromus madritensis | compact brome | Poaceae | |
| Bromus marginatus | mountain brome | Poaceae | |
| Bromus mucroglumis | sharpglume brome | Poaceae | |
| Bromus orcuttianus | Orcutt's brome | Poaceae | |
| Bromus polyanthus | Great Basin brome | Poaceae | |
| Bromus polyanthus var. paniculatus | Great Basin brome | Poaceae | |
| Bromus polyanthus var. polyanthus | Great Basin brome | Poaceae | |
| Bromus porteri | Porter brome | Poaceae | |
| Bromus racemosus | bald brome | Poaceae | |
| Bromus rubens | red brome | Poaceae | |
| Bromus secalinus | rye brome | Poaceae | |
| Bromus secalinus var. secalinus | rye brome | Poaceae | |
| Bromus sterilis | poverty brome | Poaceae | |
| Bromus tectorum | cheatgrass | Poaceae | |
| Browallia | browallia | Solanaceae | |
| Browallia eludens | bush-violet | Solanaceae | |
| Buchnera | bluehearts | Scrophulariaceae | |
| Buchnera obliqua | Arizona bluehearts | Scrophulariaceae | |
| Buddleja | butterflybush | Buddlejaceae | |
| Buddleja scordioides | escobilla butterflybush | Buddlejaceae | |
| Buddleja sessiliflora | Rio Grande butterflybush | Buddlejaceae | |
| Buddleja utahensis | Utah butterflybush | Buddlejaceae | |
| Bulbostylis | hairsedge | Cyperaceae | |
| Bulbostylis capillaris | densetuft hairsedge | Cyperaceae | |
| Bulbostylis capillaris ssp. capillaris | densetuft hairsedge | Cyperaceae | |
| Bulbostylis funckii | Funck's hairsedge | Cyperaceae | |
| Bulbostylis juncoides | rush hairsedge | Cyperaceae | |
| Bupleurum | bupleurum | Apiaceae | |
| Bupleurum lancifolium | lanceleaf thorow wax | Apiaceae | |
| Bupleurum rotundifolium | hare's ear | Apiaceae | |
| Bursera | bursera | Burseraceae | |
| Bursera fagaroides | fragrant bursera | Burseraceae | |
| Bursera fagaroides var. elongata | fragrant bursera | Burseraceae | |
| Bursera microphylla | elephant tree | Burseraceae | |
| C | |||
| Caesalpinia | nicker | Fabaceae | |
| Caesalpinia gilliesii | bird-of-paradise shrub | Fabaceae | |
| Caesalpinia mexicana | Mexican holdback | Fabaceae | |
| Caesalpinia pulcherrima | pride-of-Barbados | Fabaceae | |
| Calamagrostis | reedgrass | Poaceae | |
| Calamagrostis canadensis | bluejoint | Poaceae | |
| Calamagrostis canadensis var. canadensis | bluejoint | Poaceae | |
| Calamagrostis scopulorum | ditch reedgrass | Poaceae | |
| Calamagrostis stricta | slimstem reedgrass | Poaceae | |
| Calamagrostis stricta ssp. inexpansa | northern reedgrass | Poaceae | |
| Calamagrostis stricta ssp. stricta | slimstem reedgrass | Poaceae | |
| Calamagrostis stricta ssp. stricta var. stricta | slimstem reedgrass | Poaceae | |
| Calamovilfa | sandreed | Poaceae | |
| Calamovilfa gigantea | giant sandreed | Poaceae | |
| Calandrinia | redmaids | Portulacaceae | |
| Calandrinia ciliata | fringed redmaids | Portulacaceae | |
| Calibrachoa | calibrachoa | Solanaceae | |
| Calibrachoa parviflora | seaside petunia | Solanaceae | |
| Callaeum | callaeum | Malpighiaceae | |
| Callaeum macropterum | hillyhock | Malpighiaceae | |
| Calliandra | stickpea | Fabaceae | |
| Calliandra eriophylla | fairyduster | Fabaceae | |
| Calliandra humilis | dwarf stickpea | Fabaceae | |
| Calliandra humilis var. humilis | dwarf stickpea | Fabaceae | |
| Calliandra humilis var. reticulata | dwarf stickpea | Fabaceae | |
| Callirhoe | poppymallow | Malvaceae | |
| Callirhoe involucrata | purple poppymallow | Malvaceae | |
| Callirhoe involucrata var. involucrata | purple poppymallow | Malvaceae | |
| Callitriche | water-starwort | Callitrichaceae | |
| Callitriche hermaphroditica | northern water-starwort | Callitrichaceae | |
| Callitriche heterophylla | twoheaded water-starwort | Callitrichaceae | |
| Callitriche heterophylla ssp. heterophylla | twoheaded water-starwort | Callitrichaceae | |
| Callitriche palustris | vernal water-starwort | Callitrichaceae | |
| Calochortus | mariposa lily | Liliaceae | |
| Calochortus ambiguus | doubting mariposa lily | Liliaceae | |
| Calochortus aureus | golden mariposa lily | Liliaceae | |
| Calochortus flexuosus | winding mariposa lily | Liliaceae | |
| Calochortus gunnisonii | Gunnison's mariposa lily | Liliaceae | |
| Calochortus gunnisonii var. gunnisonii | Gunnison's mariposa lily | Liliaceae | |
| Calochortus kennedyi | desert mariposa lily | Liliaceae | |
| Calochortus kennedyi var. kennedyi | desert mariposa lily | Liliaceae | |
| Calochortus nuttallii | sego lily | Liliaceae | |
| Caltha | marsh marigold | Ranunculaceae | |
| Caltha leptosepala | white marsh marigold | Ranunculaceae | |
| Caltha leptosepala ssp. leptosepala | white marsh marigold | Ranunculaceae | |
| Caltha leptosepala ssp. leptosepala var. leptosepala | white marsh marigold | Ranunculaceae | |
| Calycoseris | tackstem | Asteraceae | |
| Calycoseris parryi | yellow tackstem | Asteraceae | |
| Calycoseris wrightii | white tackstem | Asteraceae | |
| Calylophus | sundrops | Onagraceae | |
| Calylophus hartwegii | Hartweg's sundrops | Onagraceae | |
| Calylophus hartwegii ssp. fendleri | Hartweg's sundrops | Onagraceae | |
| Calylophus hartwegii ssp. pubescens | Hartweg's sundrops | Onagraceae | |
| Calylophus lavandulifolius | lavenderleaf sundrops | Onagraceae | |
| Calylophus serrulatus | yellow sundrops | Onagraceae | |
| Calylophus toumeyi | Toumey's sundrops | Onagraceae | |
| Calypso | fairy slipper | Orchidaceae | |
| Calypso bulbosa | fairy slipper | Orchidaceae | |
| Calypso bulbosa var. americana | fairy slipper | Orchidaceae | |
| Calyptocarpus | calyptocarpus | Asteraceae | |
| Calyptocarpus vialis | straggler daisy | Asteraceae | |
| Calystegia | false bindweed | Convolvulaceae | |
| Calystegia longipes | Paiute false bindweed | Convolvulaceae | |
| Calystegia macounii | Macoun's false bindweed | Convolvulaceae | |
| Calystegia sepium | hedge false bindweed | Convolvulaceae | |
| Calystegia sepium ssp. angulata | hedge false bindweed | Convolvulaceae | |
| Camelina | false flax | Brassicaceae | |
| Camelina microcarpa | littlepod false flax | Brassicaceae | |
| Camelina sativa | gold-of-pleasure | Brassicaceae | |
| Camelina sativa ssp. sativa | gold-of-pleasure | Brassicaceae | |
| Camissonia | suncup | Onagraceae | |
| Camissonia arenaria | Fortuna Range suncup | Onagraceae | |
| Camissonia boothii | Booth's evening primrose | Onagraceae | |
| Camissonia boothii ssp. alyssoides | alyssum evening primrose | Onagraceae | |
| Camissonia boothii ssp. boothii | Booth's suncup | Onagraceae | |
| Camissonia boothii ssp. condensata | shredding suncup | Onagraceae | |
| Camissonia boothii ssp. decorticans | shredding suncup | Onagraceae | |
| Camissonia brevipes | yellow cups | Onagraceae | |
| Camissonia brevipes ssp. arizonica | golden suncup | Onagraceae | |
| Camissonia brevipes ssp. brevipes | golden suncup | Onagraceae | |
| Camissonia brevipes ssp. pallidula | pallid suncup | Onagraceae | |
| Camissonia californica | California suncup | Onagraceae | |
| Camissonia cardiophylla | heartleaf suncup | Onagraceae | |
| Camissonia cardiophylla ssp. cardiophylla | heartleaf suncup | Onagraceae | |
| Camissonia chamaenerioides | longcapsule suncup | Onagraceae | |
| Camissonia claviformis | browneyes | Onagraceae | |
| Camissonia claviformis ssp. aurantiaca | browneyes | Onagraceae | |
| Camissonia claviformis ssp. claviformis | browneyes | Onagraceae | |
| Camissonia claviformis ssp. peeblesii | Peebles' browneyes | Onagraceae | |
| Camissonia claviformis ssp. peirsonii | Peirson's browneyes | Onagraceae | |
| Camissonia claviformis ssp. rubescens | browneyes | Onagraceae | |
| Camissonia claviformis ssp. yumae | Yuma browneyes | Onagraceae | |
| Camissonia confertiflora | Grand Canyon suncup | Onagraceae | |
| Camissonia confusa | San Bernardino suncup | Onagraceae | |
| Camissonia eastwoodiae | Grand Junction camissonia | Onagraceae | |
| Camissonia exilis | Cottonwood Springs suncup | Onagraceae | |
| Camissonia gouldii | Diamond Valley suncup | Onagraceae | |
| Camissonia multijuga | froststem suncup | Onagraceae | |
| Camissonia pallida | paleyellow suncup | Onagraceae | |
| Camissonia pallida ssp. pallida | paleyellow suncup | Onagraceae | |
| Camissonia palmeri | Palmer evening primrose | Onagraceae | |
| Camissonia parryi | redclay suncup | Onagraceae | |
| Camissonia parvula | Lewis River suncup | Onagraceae | |
| Camissonia pterosperma | wingfruit suncup | Onagraceae | |
| Camissonia refracta | narrowleaf suncup | Onagraceae | |
| Camissonia scapoidea | Paiute suncup | Onagraceae | |
| Camissonia scapoidea ssp. macrocarpa | Paiute suncup | Onagraceae | |
| Camissonia scapoidea ssp. scapoidea | Paiute suncup | Onagraceae | |
| Camissonia specuicola | Kaibab suncup | Onagraceae | |
| Camissonia specuicola ssp. hesperia | Kaibab suncup | Onagraceae | |
| Camissonia specuicola ssp. specuicola | Kaibab suncup | Onagraceae | |
| Camissonia walkeri | Walker's suncup | Onagraceae | |
| Camissonia walkeri ssp. walkeri | Walker's suncup | Onagraceae | |
| Campanula | bellflower | Campanulaceae | |
| Campanula parryi | Parry's bellflower | Campanulaceae | |
| Campanula parryi var. parryi | Parry's bellflower | Campanulaceae | |
| Campanula rotundifolia | bluebell bellflower | Campanulaceae | |
| Canavalia | jackbean | Fabaceae | |
| Canavalia ensiformis | wonderbean | Fabaceae | |
| Cannabis | hemp | Cannabaceae | |
| Cannabis sativa | marijuana | Cannabaceae | |
| Cannabis sativa ssp. sativa | marijuana | Cannabaceae | |
| Cannabis sativa ssp. sativa var. sativa | marijuana | Cannabaceae | |
| Canotia | canotia | Celastraceae | |
| Canotia holacantha | crucifixion thorn | Celastraceae | |
| Capsella | capsella | Brassicaceae | |
| Capsella bursa-pastoris | shepherd's purse | Brassicaceae | |
| Capsicum | pepper | Solanaceae | |
| Capsicum annuum | cayenne pepper | Solanaceae | |
| Capsicum annuum var. glabriusculum | cayenne pepper | Solanaceae | |
| Cardamine | bittercress | Brassicaceae | |
| Cardamine cordifolia | heartleaf bittercress | Brassicaceae | |
| Cardamine cordifolia var. cordifolia | heartleaf bittercress | Brassicaceae | |
| Cardamine hirsuta | hairy bittercress | Brassicaceae | |
| Cardamine parviflora | sand bittercress | Brassicaceae | |
| Cardamine parviflora var. arenicola | sand bittercress | Brassicaceae | |
| Cardaria | whitetop | Brassicaceae | |
| Cardaria draba | whitetop | Brassicaceae | |
| Cardaria pubescens | hairy whitetop | Brassicaceae | |
| Cardiospermum | balloonvine | Sapindaceae | |
| Cardiospermum corindum | faux persil | Sapindaceae | |
| Carduus | plumeless thistle | Asteraceae | |
| Carduus nutans | nodding plumeless thistle | Asteraceae | |
| Carex | sedge | Cyperaceae | |
| Carex agrostoides | grassleaf sedge | Cyperaceae | |
| Carex albonigra | blackandwhite sedge | Cyperaceae | |
| Carex alma | sturdy sedge | Cyperaceae | |
| Carex aquatilis | water sedge | Cyperaceae | |
| Carex aquatilis var. aquatilis | water sedge | Cyperaceae | |
| Carex atherodes | wheat sedge | Cyperaceae | |
| Carex athrostachya | slenderbeak sedge | Cyperaceae | |
| Carex aurea | golden sedge | Cyperaceae | |
| Carex bella | southwestern showy sedge | Cyperaceae | |
| Carex bolanderi | Bolander's sedge | Cyperaceae | |
| Carex brevior | shortbeak sedge | Cyperaceae | |
| Carex canescens | silvery sedge | Cyperaceae | |
| Carex canescens ssp. canescens | silvery sedge | Cyperaceae | |
| Carex chihuahuensis | Chihuahuan sedge | Cyperaceae | |
| Carex conoidea | openfield sedge | Cyperaceae | |
| Carex curatorum | Kaibab sedge | Cyperaceae | |
| Carex disperma | softleaf sedge | Cyperaceae | |
| Carex douglasii | Douglas' sedge | Cyperaceae | |
| Carex duriuscula | needleleaf sedge | Cyperaceae | |
| Carex ebenea | ebony sedge | Cyperaceae | |
| Carex elynoides | blackroot sedge | Cyperaceae | |
| Carex filifolia | threadleaf sedge | Cyperaceae | |
| Carex geophila | White Mountain sedge | Cyperaceae | |
| Carex hassei | salt sedge | Cyperaceae | |
| Carex haydeniana | cloud sedge | Cyperaceae | |
| Carex heteroneura | different-nerve sedge | Cyperaceae | |
| Carex heteroneura var. chalciolepis | Holm sedge | Cyperaceae | |
| Carex heteroneura var. epapillosa | different-nerve sedge | Cyperaceae | |
| Carex hystericina | bottlebrush sedge | Cyperaceae | |
| Carex interior | inland sedge | Cyperaceae | |
| Carex lativena | broadvein sedge | Cyperaceae | |
| Carex lenticularis | lakeshore sedge | Cyperaceae | |
| Carex lenticularis var. lipocarpa | Kellogg's sedge | Cyperaceae | |
| Carex leptopoda | taperfruit shortscale sedge | Cyperaceae | |
| Carex leucodonta | Huachuca Mountain sedge | Cyperaceae | |
| Carex mariposana | Mariposa sedge | Cyperaceae | |
| Carex meadii | Mead's sedge | Cyperaceae | |
| Carex microdonta | littletooth sedge | Cyperaceae | |
| Carex microptera | smallwing sedge | Cyperaceae | |
| Carex nebrascensis | Nebraska sedge | Cyperaceae | |
| Carex occidentalis | western sedge | Cyperaceae | |
| Carex oreocharis | grassyslope sedge | Cyperaceae | |
| Carex pellita | woolly sedge | Cyperaceae | |
| Carex petasata | Liddon sedge | Cyperaceae | |
| Carex planostachys | cedar sedge | Cyperaceae | |
| Carex praegracilis | clustered field sedge | Cyperaceae | |
| Carex rossii | Ross' sedge | Cyperaceae | |
| Carex scoparia | broom sedge | Cyperaceae | |
| Carex scoparia var. scoparia | broom sedge | Cyperaceae | |
| Carex scopulorum | mountain sedge | Cyperaceae | |
| Carex scopulorum var. bracteosa | mountain sedge | Cyperaceae | |
| Carex senta | swamp carex | Cyperaceae | |
| Carex serratodens | twotooth sedge | Cyperaceae | |
| Carex siccata | dryspike sedge | Cyperaceae | |
| Carex simulata | analogue sedge | Cyperaceae | |
| Carex specuicola | Navajo sedge | Cyperaceae | |
| Carex spissa | San Diego sedge | Cyperaceae | |
| Carex stipata | awlfruit sedge | Cyperaceae | |
| Carex stipata var. stipata | owlfruit sedge | Cyperaceae | |
| Carex subfusca | brown sedge | Cyperaceae | |
| Carex tahoensis | Tahoe sedge | Cyperaceae | |
| Carex thurberi | Thurber's sedge | Cyperaceae | |
| Carex ultra | Cochise sedge | Cyperaceae | |
| Carex vallicola | valley sedge | Cyperaceae | |
| Carex vallicola var. rusbyi | Rusby's sedge | Cyperaceae | |
| Carex vesicaria | blister sedge | Cyperaceae | |
| Carex vesicaria var. vesicaria | blister sedge | Cyperaceae | |
| Carex vulpinoidea | fox sedge | Cyperaceae | |
| Carex vulpinoidea var. vulpinoidea | fox sedge | Cyperaceae | |
| Carex wootonii | Wooton's sedge | Cyperaceae | |
| Carlowrightia | wrightwort | Acanthaceae | |
| Carlowrightia arizonica | Arizona wrightwort | Acanthaceae | |
| Carlowrightia linearifolia | heath wrightwort | Acanthaceae | |
| Carminatia | carminatia | Asteraceae | |
| Carminatia tenuiflora | plumeweed | Asteraceae | |
| Carnegiea | saguaro | Cactaceae | |
| Carnegiea gigantea | saguaro | Cactaceae | |
| Carphochaete | bristlehead | Asteraceae | |
| Carphochaete bigelovii | Bigelow's bristlehead | Asteraceae | |
| Carthamus | distaff thistle | Asteraceae | |
| Carthamus lanatus | woolly distaff thistle | Asteraceae | |
| Carthamus lanatus ssp. creticus | woolly distaff thistle | Asteraceae | |
| Carthamus tinctorius | safflower | Asteraceae | |
| Castalis | castalis | Asteraceae | |
| Castalis tragus | Cape marigold | Asteraceae | |
| Castela | castela | Simaroubaceae | |
| Castela emoryi | crucifixion thorn | Simaroubaceae | |
| Castilleja | Indian paintbrush | Scrophulariaceae | |
| Castilleja angustifolia | northwestern Indian paintbrush | Scrophulariaceae | |
| Castilleja angustifolia var. dubia | Scrophulariaceae | ||
| Castilleja attenuata | attenuate Indian paintbrush | Scrophulariaceae | |
| Castilleja austromontana | Rincon Mountain Indian paintbrush | Scrophulariaceae | |
| Castilleja exserta | exserted Indian paintbrush | Scrophulariaceae | |
| Castilleja exserta ssp. exserta | exserted Indian paintbrush | Scrophulariaceae | |
| Castilleja integra | wholeleaf Indian paintbrush | Scrophulariaceae | |
| Castilleja integra var. gloriosa | wholeleaf Indian paintbrush | Scrophulariaceae | |
| Castilleja integra var. integra | wholeleaf Indian paintbrush | Scrophulariaceae | |
| Castilleja kaibabensis | Kaibab Plateau Indian paintbrush | Scrophulariaceae | |
| Castilleja lanata | Sierra woolly Indian paintbrush | Scrophulariaceae | |
| Castilleja lanata ssp. lanata | Sierra woolly Indian paintbrush | Scrophulariaceae | |
| Castilleja linariifolia | Wyoming Indian paintbrush | Scrophulariaceae | |
| Castilleja lineata | marshmeadow Indian paintbrush | Scrophulariaceae | |
| Castilleja miniata | giant red Indian paintbrush | Scrophulariaceae | |
| Castilleja miniata ssp. miniata | giant red Indian paintbrush | Scrophulariaceae | |
| Castilleja minor | lesser Indian paintbrush | Scrophulariaceae | |
| Castilleja minor ssp. minor | lesser Indian paintbrush | Scrophulariaceae | |
| Castilleja minor ssp. spiralis | lesser Indian paintbrush | Scrophulariaceae | |
| Castilleja nervata | Trans-Pecos Indian paintbrush | Scrophulariaceae | |
| Castilleja patriotica | Huachuca Mountain Indian paintbrush | Scrophulariaceae | |
| Castilleja sessiliflora | downy paintedcup | Scrophulariaceae | |
| Castilleja sulphurea | sulphur Indian paintbrush | Scrophulariaceae | |
| Castilleja tenuiflora | Santa Catalina Indian paintbrush | Scrophulariaceae | |
| Catabrosa | whorlgrass | Poaceae | |
| Catabrosa aquatica | water whorlgrass | Poaceae | |
| Catabrosa aquatica var. aquatica | water whorlgrass | Poaceae | |
| Catalpa | catalpa | Bignoniaceae | |
| Catalpa bignonioides | southern catalpa | Bignoniaceae | |
| Cathestecum | false grama | Poaceae | |
| Cathestecum erectum | false grama | Poaceae | |
| Caulanthus | wild cabbage | Brassicaceae | |
| Caulanthus cooperi | Cooper's wild cabbage | Brassicaceae | |
| Ceanothus | ceanothus | Rhamnaceae | |
| Ceanothus fendleri | Fendler's ceanothus | Rhamnaceae | |
| Ceanothus greggii | desert ceanothus | Rhamnaceae | |
| Ceanothus greggii var. greggii | desert ceanothus | Rhamnaceae | |
| Ceanothus greggii var. perplexans | desert ceanothus | Rhamnaceae | |
| Ceanothus greggii var. vestitus | Mojave ceanothus | Rhamnaceae | |
| Ceanothus integerrimus | deerbrush | Rhamnaceae | |
| Ceanothus martinii | Martin's ceanothus | Rhamnaceae | |
| Celtis | hackberry | Ulmaceae | |
| Celtis ehrenbergiana | spiny hackberry | Ulmaceae | |
| Celtis laevigata | sugarberry | Ulmaceae | |
| Celtis laevigata var. brevipes | sugarberry | Ulmaceae | |
| Celtis laevigata var. reticulata | netleaf hackberry | Ulmaceae | |
| Cenchrus | sandbur | Poaceae | |
| Cenchrus echinatus | southern sandbur | Poaceae | |
| Cenchrus longispinus | mat sandbur | Poaceae | |
| Cenchrus spinifex | coastal sandbur | Poaceae | |
| Centaurea | knapweed | Asteraceae | |
| Centaurea americana | American star-thistle | Asteraceae | |
| Centaurea calcitrapa | red star-thistle | Asteraceae | |
| Centaurea cyanus | garden cornflower | Asteraceae | |
| Centaurea diffusa | diffuse knapweed | Asteraceae | |
| Centaurea melitensis | Maltese star-thistle | Asteraceae | |
| Centaurea rothrockii | Rothrock's knapweed | Asteraceae | |
| Centaurea solstitialis | yellow star-thistle | Asteraceae | |
| Centaurea stoebe | spotted knapweed | Asteraceae | |
| Centaurea stoebe ssp. micranthos | spotted knapweed | Asteraceae | |
| Centaurium | centaury | Gentianaceae | |
| Centaurium arizonicum | Arizona centaury | Gentianaceae | |
| Centaurium exaltatum | desert centaury | Gentianaceae | |
| Centaurium nudicaule | Santa Catalina Mountain centaury | Gentianaceae | |
| Centranthus | centranthus | Valerianaceae | |
| Centranthus ruber | red valerian | Valerianaceae | |
| Centromadia | Asteraceae | ||
| Centromadia pungens | common tarweed | Asteraceae | |
| Centromadia pungens ssp. pungens | common tarweed | Asteraceae | |
| Centrostegia | centrostegia | Polygonaceae | |
| Centrostegia thurberi | red triangles | Polygonaceae | |
| Cephalanthus | buttonbush | Rubiaceae | |
| Cephalanthus occidentalis | common buttonbush | Rubiaceae | |
| Cerastium | mouse-ear chickweed | Caryophyllaceae | |
| Cerastium arvense | field chickweed | Caryophyllaceae | |
| Cerastium arvense ssp. strictum | field chickweed | Caryophyllaceae | |
| Cerastium beeringianum | Bering chickweed | Caryophyllaceae | |
| Cerastium beeringianum ssp. earlei | Bering chickweed | Caryophyllaceae | |
| Cerastium brachypodum | shortstalk chickweed | Caryophyllaceae | |
| Cerastium fontanum | common mouse-ear chickweed | Caryophyllaceae | |
| Cerastium fontanum ssp. vulgare | big chickweed | Caryophyllaceae | |
| Cerastium gracile | slender chickweed | Caryophyllaceae | |
| Cerastium nutans | nodding chickweed | Caryophyllaceae | |
| Cerastium nutans var. nutans | nodding chickweed | Caryophyllaceae | |
| Cerastium nutans var. obtectum | nodding chickweed | Caryophyllaceae | |
| Cerastium sordidum | Chihuahuan chickweed | Caryophyllaceae | |
| Cerastium texanum | Texas chickweed | Caryophyllaceae | |
| Ceratocephala | curveseed butterwort | Ranunculaceae | |
| Ceratocephala testiculata | curveseed butterwort | Ranunculaceae | |
| Ceratonia | ceratonia | Fabaceae | |
| Ceratonia siliqua | St. John's bread | Fabaceae | |
| Ceratophyllum | hornwort | Ceratophyllaceae | |
| Ceratophyllum demersum | coon's tail | Ceratophyllaceae | |
| Cercis | redbud | Fabaceae | |
| Cercis orbiculata | California redbud | Fabaceae | |
| Cercocarpus | mountain mahogany | Rosaceae | |
| Cercocarpus intricatus | littleleaf mountain mahogany | Rosaceae | |
| Cercocarpus ledifolius | curl-leaf mountain mahogany | Rosaceae | |
| Cercocarpus ledifolius var. intercedens | curl-leaf mountain mahogany | Rosaceae | |
| Cercocarpus ledifolius var. ledifolius | curl-leaf mountain mahogany | Rosaceae | |
| Cercocarpus montanus | alderleaf mountain mahogany | Rosaceae | |
| Cercocarpus montanus var. glaber | birchleaf mountain mahogany | Rosaceae | |
| Cercocarpus montanus var. montanus | alderleaf mountain mahogany | Rosaceae | |
| Cercocarpus montanus var. paucidentatus | hairy mountain mahogany | Rosaceae | |
| Cevallia | stinging serpent | Loasaceae | |
| Cevallia sinuata | stinging serpent | Loasaceae | |
| Chaenactis | pincushion | Asteraceae | |
| Chaenactis carphoclinia | pebble pincushion | Asteraceae | |
| Chaenactis carphoclinia var. carphoclinia | pebble pincushion | Asteraceae | |
| Chaenactis douglasii | Douglas' dustymaiden | Asteraceae | |
| Chaenactis douglasii var. douglasii | Douglas' dustymaiden | Asteraceae | |
| Chaenactis fremontii | pincushion flower | Asteraceae | |
| Chaenactis macrantha | bighead dustymaiden | Asteraceae | |
| Chaenactis stevioides | Esteve's pincushion | Asteraceae | |
| Chaenactis xantiana | fleshcolor pincushion | Asteraceae | |
| Chaerophyllum | chervil | Apiaceae | |
| Chaerophyllum tainturieri | hairyfruit chervil | Apiaceae | |
| Chaerophyllum tainturieri var. tainturieri | hairyfruit chervil | Apiaceae | |
| Chaetopappa | leastdaisy | Asteraceae | |
| Chaetopappa ericoides | rose heath | Asteraceae | |
| Chamaebatiaria | desert sweet | Rosaceae | |
| Chamaebatiaria millefolium | desert sweet | Rosaceae | |
| Chamaechaenactis | chamaechaenactis | Asteraceae | |
| Chamaechaenactis scaposa | fullstem | Asteraceae | |
| Chamaechaenactis scaposa var. scaposa | fullstem | Asteraceae | |
| Chamaecrista | sensitive pea | Fabaceae | |
| Chamaecrista absus | tropical sensitive pea | Fabaceae | |
| Chamaecrista absus var. meonandra | tropical sensitive pea | Fabaceae | |
| Chamaecrista nictitans | sensitive partridge pea | Fabaceae | |
| Chamaecrista nictitans ssp. nictitans | sensitive partridge pea | Fabaceae | |
| Chamaecrista nictitans ssp. nictitans var. leptadenia | sensitive partridge pea | Fabaceae | |
| Chamaecrista serpens | slender sensitive pea | Fabaceae | |
| Chamaecrista serpens var. wrightii | Wright's sensitive pea | Fabaceae | |
| Chamaesaracha | five eyes | Solanaceae | |
| Chamaesaracha coronopus | greenleaf five eyes | Solanaceae | |
| Chamaesaracha sordida | hairy five eyes | Solanaceae | |
| Chamaesyce | sandmat | Euphorbiaceae | |
| Chamaesyce abramsiana | Abrams' sandmat | Euphorbiaceae | |
| Chamaesyce albomarginata | whitemargin sandmat | Euphorbiaceae | |
| Chamaesyce arizonica | Arizona sandmat | Euphorbiaceae | |
| Chamaesyce capitellata | head sandmat | Euphorbiaceae | |
| Chamaesyce chaetocalyx | bristlecup sandmat | Euphorbiaceae | |
| Chamaesyce chaetocalyx var. chaetocalyx | bristlecup sandmat | Euphorbiaceae | |
| Chamaesyce dioica | royal sandmat | Euphorbiaceae | |
| Chamaesyce fendleri | Fendler's sandmat | Euphorbiaceae | |
| Chamaesyce florida | Chiricahua Mountain sandmat | Euphorbiaceae | |
| Chamaesyce glyptosperma | ribseed sandmat | Euphorbiaceae | |
| Chamaesyce gracillima | Mexican sandmat | Euphorbiaceae | |
| Chamaesyce hirta | pillpod sandmat | Euphorbiaceae | |
| Chamaesyce hypericifolia | graceful sandmat | Euphorbiaceae | |
| Chamaesyce hyssopifolia | hyssopleaf sandmat | Euphorbiaceae | |
| Chamaesyce maculata | spotted sandmat | Euphorbiaceae | |
| Chamaesyce melanadenia | red-gland spurge | Euphorbiaceae | |
| Chamaesyce micromera | Sonoran sandmat | Euphorbiaceae | |
| Chamaesyce ocellata | Contura Creek sandmat | Euphorbiaceae | |
| Chamaesyce ocellata ssp. arenicola | Contura Creek sandmat | Euphorbiaceae | |
| Chamaesyce parryi | Parry's sandmat | Euphorbiaceae | |
| Chamaesyce pediculifera | Carrizo Mountain sandmat | Euphorbiaceae | |
| Chamaesyce platysperma | flatseed sandmat | Euphorbiaceae | |
| Chamaesyce polycarpa | smallseed sandmat | Euphorbiaceae | |
| Chamaesyce prostrata | prostrate sandmat | Euphorbiaceae | |
| Chamaesyce revoluta | threadstem sandmat | Euphorbiaceae | |
| Chamaesyce serpens | matted sandmat | Euphorbiaceae | |
| Chamaesyce serpyllifolia | thymeleaf sandmat | Euphorbiaceae | |
| Chamaesyce serpyllifolia ssp. serpyllifolia | thymeleaf sandmat | Euphorbiaceae | |
| Chamaesyce serrula | sawtooth sandmat | Euphorbiaceae | |
| Chamaesyce setiloba | Yuma sandmat | Euphorbiaceae | |
| Chamaesyce stictospora | slimseed sandmat | Euphorbiaceae | |
| Chamaesyce trachysperma | San Pedro River sandmat | Euphorbiaceae | |
| Chamaesyce vermiculata | wormseed sandmat | Euphorbiaceae | |
| Chamerion | fireweed | Onagraceae | |
| Chamerion angustifolium | fireweed | Onagraceae | |
| Chamerion angustifolium ssp. circumvagum | fireweed | Onagraceae | |
| Chasmanthium | woodoats | Poaceae | |
| Chasmanthium latifolium | Indian woodoats | Poaceae | |
| Cheilanthes | lipfern | Pteridaceae | |
| Cheilanthes alabamensis | Alabama lipfern | Pteridaceae | |
| Cheilanthes arizonica | Arizona lipfern | Pteridaceae | |
| Cheilanthes bonariensis | golden lipfern | Pteridaceae | |
| Cheilanthes covillei | Coville's lipfern | Pteridaceae | |
| Cheilanthes eatonii | Eaton's lipfern | Pteridaceae | |
| Cheilanthes feei | slender lipfern | Pteridaceae | |
| Cheilanthes fendleri | Fendler's lipfern | Pteridaceae | |
| Cheilanthes lendigera | nitbearing lipfern | Pteridaceae | |
| Cheilanthes lindheimeri | fairyswords | Pteridaceae | |
| Cheilanthes parishii | Pteridaceae | ||
| Cheilanthes parryi | Parry's lipfern | Pteridaceae | |
| Cheilanthes pringlei | Pringle's lipfern | Pteridaceae | |
| Cheilanthes tomentosa | woolly lipfern | Pteridaceae | |
| Cheilanthes villosa | villous lipfern | Pteridaceae | |
| Cheilanthes wootonii | beaded lipfern | Pteridaceae | |
| Cheilanthes wrightii | Wright's lipfern | Pteridaceae | |
| Cheilanthes yavapensis | graceful lipfern | Pteridaceae | |
| Chenopodium | goosefoot | Chenopodiaceae | |
| Chenopodium album | lambsquarters | Chenopodiaceae | |
| Chenopodium album var. album | lambsquarters | Chenopodiaceae | |
| Chenopodium ambrosioides | Mexican tea | Chenopodiaceae | |
| Chenopodium ambrosioides var. ambrosioides | Mexican tea | Chenopodiaceae | |
| Chenopodium atrovirens | pinyon goosefoot | Chenopodiaceae | |
| Chenopodium berlandieri | pitseed goosefoot | Chenopodiaceae | |
| Chenopodium berlandieri var. berlandieri | pitseed goosefoot | Chenopodiaceae | |
| Chenopodium berlandieri var. sinuatum | pitseed goosefoot | Chenopodiaceae | |
| Chenopodium berlandieri var. zschackii | Zschack's goosefoot | Chenopodiaceae | |
| Chenopodium botrys | Jerusalem oak goosefoot | Chenopodiaceae | |
| Chenopodium capitatum | blite goosefoot | Chenopodiaceae | |
| Chenopodium desiccatum | aridland goosefoot | Chenopodiaceae | |
| Chenopodium ficifolium | figleaf goosefoot | Chenopodiaceae | |
| Chenopodium fremontii | Fremont's goosefoot | Chenopodiaceae | |
| Chenopodium fremontii var. fremontii | Fremont's goosefoot | Chenopodiaceae | |
| Chenopodium graveolens | fetid goosefoot | Chenopodiaceae | |
| Chenopodium hians | hians goosefoot | Chenopodiaceae | |
| Chenopodium incanum | mealy goosefoot | Chenopodiaceae | |
| Chenopodium incanum var. elatum | mealy goosefoot | Chenopodiaceae | |
| Chenopodium incanum var. incanum | mealy goosefoot | Chenopodiaceae | |
| Chenopodium incanum var. occidentale | mealy goosefoot | Chenopodiaceae | |
| Chenopodium leptophyllum | narrowleaf goosefoot | Chenopodiaceae | |
| Chenopodium murale | nettleleaf goosefoot | Chenopodiaceae | |
| Chenopodium neomexicanum | New Mexico goosefoot | Chenopodiaceae | |
| Chenopodium neomexicanum var. neomexicanum | New Mexico goosefoot | Chenopodiaceae | |
| Chenopodium pratericola | desert goosefoot | Chenopodiaceae | |
| Chenopodium pumilio | clammy goosefoot | Chenopodiaceae | |
| Chenopodium rubrum | red goosefoot | Chenopodiaceae | |
| Chenopodium salinum | Rocky Mountain goosefoot | Chenopodiaceae | |
| Chenopodium watsonii | Watson's goosefoot | Chenopodiaceae | |
| Chilopsis | desert willow | Bignoniaceae | |
| Chilopsis linearis | desert willow | Bignoniaceae | |
| Chilopsis linearis ssp. arcuata | desert willow | Bignoniaceae | |
| Chimaphila | prince's pine | Pyrolaceae | |
| Chimaphila maculata | striped prince's pine | Pyrolaceae | |
| Chimaphila umbellata | pipsissewa | Pyrolaceae | |
| Chimaphila umbellata ssp. acuta | pipsissewa | Pyrolaceae | |
| Chloracantha | chloracantha | Asteraceae | |
| Chloracantha spinosa | spiny chloracantha | Asteraceae | |
| Chloris | windmill grass | Poaceae | |
| Chloris cucullata | hooded windmill grass | Poaceae | |
| Chloris gayana | Rhodes grass | Poaceae | |
| Chloris subdolichostachya | shortspike windmill grass | Poaceae | |
| Chloris verticillata | tumble windmill grass | Poaceae | |
| Chloris virgata | feather fingergrass | Poaceae | |
| Choisya | Mexican orange | Rutaceae | |
| Choisya dumosa | Mexican orange | Rutaceae | |
| Choisya dumosa var. arizonica | Arizonia orange | Rutaceae | |
| Choisya dumosa var. mollis | Mexican orange | Rutaceae | |
| Chorispora | chorispora | Brassicaceae | |
| Chorispora tenella | crossflower | Brassicaceae | |
| Chorizanthe | spineflower | Polygonaceae | |
| Chorizanthe brevicornu | brittle spineflower | Polygonaceae | |
| Chorizanthe brevicornu var. brevicornu | brittle spineflower | Polygonaceae | |
| Chorizanthe corrugata | wrinkled spineflower | Polygonaceae | |
| Chorizanthe rigida | devil's spineflower | Polygonaceae | |
| Chorizanthe watsonii | fivetooth spineflower | Polygonaceae | |
| Chromolaena | thoroughwort | Asteraceae | |
| Chromolaena bigelovii | Bigelow's thoroughwort | Asteraceae | |
| Chrysothamnus | rabbitbrush | Asteraceae | |
| Chrysothamnus baileyi | Bailey's rabbitbrush | Asteraceae | |
| Chrysothamnus depressus | longflower rabbitbrush | Asteraceae | |
| Chrysothamnus greenei | Greene's rabbitbrush | Asteraceae | |
| Chrysothamnus linifolius | spearleaf rabbitbrush | Asteraceae | |
| Chrysothamnus molestus | Arizona rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus | yellow rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus ssp. axillaris | yellow rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus ssp. lanceolatus | yellow rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus ssp. planifolius | yellow rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus ssp. puberulus | yellow rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus ssp. viscidiflorus | yellow rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. stenophyllus | yellow rabbitbrush | Asteraceae | |
| Chrysothamnus viscidiflorus ssp. viscidiflorus var. viscidiflorus | yellow rabbitbrush | Asteraceae | |
| Cichorium | chicory | Asteraceae | |
| Cichorium intybus | chicory | Asteraceae | |
| Cicuta | water hemlock | Apiaceae | |
| Cicuta maculata | spotted water hemlock | Apiaceae | |
| Cicuta maculata var. angustifolia | spotted water hemlock | Apiaceae | |
| Cicuta maculata var. bolanderi | spotted water hemlock | Apiaceae | |
| Cicuta maculata var. maculata | spotted water hemlock | Apiaceae | |
| Cinna | woodreed | Poaceae | |
| Cinna latifolia | drooping woodreed | Poaceae | |
| Circaea | enchanter's nightshade | Onagraceae | |
| Circaea alpina | small enchanter's nightshade | Onagraceae | |
| Circaea alpina ssp. alpina | small enchanter's nightshade | Onagraceae | |
| Circaea alpina ssp. pacifica | small enchanter's nightshade | Onagraceae | |
| Cirsium | thistle | Asteraceae | |
| Cirsium arizonicum | Arizona thistle | Asteraceae | |
| Cirsium arvense | Canada thistle | Asteraceae | |
| Cirsium chellyense | queen thistle | Asteraceae | |
| Cirsium chuskaense | monarch thistle | Asteraceae | |
| Cirsium grahamii | Graham's thistle | Asteraceae | |
| Cirsium mohavense | Mojave thistle | Asteraceae | |
| Cirsium navajoense | Navajo thistle | Asteraceae | |
| Cirsium neomexicanum | New Mexico thistle | Asteraceae | |
| Cirsium ochrocentrum | yellowspine thistle | Asteraceae | |
| Cirsium ochrocentrum ssp. martinii | Asteraceae | ||
| Cirsium ochrocentrum ssp. ochrocentrum | yellowspine thistle | Asteraceae | |
| Cirsium parryi | Parry's thistle | Asteraceae | |
| Cirsium parryi ssp. mogollonicum | Mogollon thistle | Asteraceae | |
| Cirsium parryi ssp. parryi | Parry's thistle | Asteraceae | |
| Cirsium rothrockii | Rothrock's thistle | Asteraceae | |
| Cirsium rusbyi | Rusby's thistle | Asteraceae | |
| Cirsium rydbergii | Rydberg's thistle | Asteraceae | |
| Cirsium scariosum | meadow thistle | Asteraceae | |
| Cirsium undulatum | wavyleaf thistle | Asteraceae | |
| Cirsium undulatum var. undulatum | wavyleaf thistle | Asteraceae | |
| Cirsium virginense | virgin thistle | Asteraceae | |
| Cirsium vulgare | bull thistle | Asteraceae | |
| Cirsium wheeleri | Wheeler's thistle | Asteraceae | |
| Cirsium wrightii | Wright's thistle | Asteraceae | |
| Cissus | treebine | Vitaceae | |
| Cissus trifoliata | sorrelvine | Vitaceae | |
| Cistanthe | pussypaws | Portulacaceae | |
| Cistanthe ambigua | desert pussypaws | Portulacaceae | |
| Cistanthe monandra | common pussypaws | Portulacaceae | |
| Cistanthe parryi | Parry's pussypaws | Portulacaceae | |
| Cistanthe parryi var. arizonica | Arizona pussypaws | Portulacaceae | |
| Citrullus | watermelon | Cucurbitaceae | |
| Citrullus lanatus | watermelon | Cucurbitaceae | |
| Citrullus lanatus var. lanatus | watermelon | Cucurbitaceae | |
| Cladium | sawgrass | Cyperaceae | |
| Cladium californicum | California sawgrass | Cyperaceae | |
| Clarkia | clarkia | Onagraceae | |
| Clarkia epilobioides | canyon clarkia | Onagraceae | |
| Clarkia purpurea | winecup clarkia | Onagraceae | |
| Clarkia purpurea ssp. quadrivulnera | winecup clarkia | Onagraceae | |
| Clarkia rhomboidea | diamond clarkia | Onagraceae | |
| Claytonia | springbeauty | Portulacaceae | |
| Claytonia parviflora | streambank springbeauty | Portulacaceae | |
| Claytonia parviflora ssp. parviflora | streambank springbeauty | Portulacaceae | |
| Claytonia parviflora ssp. utahensis | streambank springbeauty | Portulacaceae | |
| Claytonia perfoliata | miner's lettuce | Portulacaceae | |
| Claytonia perfoliata ssp. intermontana | miner's lettuce | Portulacaceae | |
| Claytonia perfoliata ssp. mexicana | miner's lettuce | Portulacaceae | |
| Claytonia perfoliata ssp. perfoliata | miner's lettuce | Portulacaceae | |
| Claytonia rosea | western springbeauty | Portulacaceae | |
| Claytonia rubra | redstem springbeauty | Portulacaceae | |
| Claytonia rubra ssp. depressa | redstem springbeauty | Portulacaceae | |
| Claytonia rubra ssp. rubra | redstem springbeauty | Portulacaceae | |
| Clematis | leather flower | Ranunculaceae | |
| Clematis bigelovii | Bigelow's leather flower | Ranunculaceae | |
| Clematis columbiana | rock clematis | Ranunculaceae | |
| Clematis columbiana var. columbiana | rock clematis | Ranunculaceae | |
| Clematis drummondii | Drummond's clematis | Ranunculaceae | |
| Clematis hirsutissima | hairy clematis | Ranunculaceae | |
| Clematis hirsutissima var. arizonica | Arizona clematis | Ranunculaceae | |
| Clematis hirsutissima var. hirsutissima | hairy clematis | Ranunculaceae | |
| Clematis ligusticifolia | western white clematis | Ranunculaceae | |
| Clematis ligusticifolia var. ligusticifolia | western white clematis | Ranunculaceae | |
| Clematis palmeri | Palmer's leather flower | Ranunculaceae | |
| Cleome | spiderflower | Capparaceae | |
| Cleome isomeris | bladderpod spiderflower | Capparaceae | |
| Cleome lutea | yellow spiderflower | Capparaceae | |
| Cleome lutea var. jonesii | Jones spiderflower | Capparaceae | |
| Cleome lutea var. lutea | yellow spiderflower | Capparaceae | |
| Cleome multicaulis | slender spiderflower | Capparaceae | |
| Cleome serrulata | Rocky Mountain beeplant | Capparaceae | |
| Cleomella | stinkweed | Capparaceae | |
| Cleomella longipes | Chiricahua Mountain stinkweed | Capparaceae | |
| Cleomella obtusifolia | Mojave cleomella | Capparaceae | |
| Cleomella parviflora | slender cleomella | Capparaceae | |
| Cleomella plocasperma | twisted cleomella | Capparaceae | |
| Clinopodium | clinopodium | Lamiaceae | |
| Clinopodium vulgare | wild basil | Lamiaceae | |
| Clitoria | pigeonwings | Fabaceae | |
| Clitoria mariana | Atlantic pigeonwings | Fabaceae | |
| Cnicus | cnicus | Asteraceae | |
| Cnicus benedictus | blessed thistle | Asteraceae | |
| Cnidoscolus | cnidoscolus | Euphorbiaceae | |
| Cnidoscolus angustidens | mala mujer | Euphorbiaceae | |
| Cocculus | coralbead | Menispermaceae | |
| Cocculus diversifolius | snailseed | Menispermaceae | |
| Coleogyne | coleogyne | Rosaceae | |
| Coleogyne ramosissima | blackbrush | Rosaceae | |
| Collinsia | blue eyed Mary | Scrophulariaceae | |
| Collinsia parviflora | maiden blue eyed Mary | Scrophulariaceae | |
| Collomia | trumpet | Polemoniaceae | |
| Collomia grandiflora | grand collomia | Polemoniaceae | |
| Collomia linearis | tiny trumpet | Polemoniaceae | |
| Cologania | cologania | Fabaceae | |
| Cologania angustifolia | longleaf cologania | Fabaceae | |
| Cologania obovata | Lemmon's cologania | Fabaceae | |
| Cologania pallida | pale cologania | Fabaceae | |
| Colubrina | nakedwood | Rhamnaceae | |
| Colubrina californica | Las Animas nakedwood | Rhamnaceae | |
| Comandra | bastard toadflax | Santalaceae | |
| Comandra umbellata | bastard toadflax | Santalaceae | |
| Comandra umbellata ssp. californica | California bastard toadflax | Santalaceae | |
| Comandra umbellata ssp. pallida | pale bastard toadflax | Santalaceae | |
| Commelina | dayflower | Commelinaceae | |
| Commelina dianthifolia | birdbill dayflower | Commelinaceae | |
| Commelina dianthifolia var. dianthifolia | birdbill dayflower | Commelinaceae | |
| Commelina dianthifolia var. longispatha | birdbill dayflower | Commelinaceae | |
| Commelina erecta | whitemouth dayflower | Commelinaceae | |
| Commelina erecta var. angustifolia | whitemouth dayflower | Commelinaceae | |
| Commelina erecta var. deamiana | whitemouth dayflower | Commelinaceae | |
| Commelina erecta var. erecta | whitemouth dayflower | Commelinaceae | |
| Condalia | snakewood | Rhamnaceae | |
| Condalia correllii | Correll's snakewood | Rhamnaceae | |
| Condalia ericoides | javelina bush | Rhamnaceae | |
| Condalia globosa | bitter snakewood | Rhamnaceae | |
| Condalia globosa var. pubescens | bitter snakewood | Rhamnaceae | |
| Condalia warnockii | Warnock's snakewood | Rhamnaceae | |
| Condalia warnockii var. kearneyana | Kearney's snakewood | Rhamnaceae | |
| Conioselinum | hemlockparsley | Apiaceae | |
| Conioselinum mexicanum | Mexican hemlockparsley | Apiaceae | |
| Conioselinum scopulorum | Rocky Mountain hemlockparsley | Apiaceae | |
| Conium | poison hemlock | Apiaceae | |
| Conium maculatum | poison hemlock | Apiaceae | |
| Conoclinium | thoroughwort | Asteraceae | |
| Conoclinium greggii | palmleaf thoroughwort | Asteraceae | |
| Conopholis | cancer-root | Orobanchaceae | |
| Conopholis alpina | alpine cancer-root | Orobanchaceae | |
| Conopholis alpina var. mexicana | Mexican cancer-root | Orobanchaceae | |
| Conringia | hare's ear mustard | Brassicaceae | |
| Conringia orientalis | hare's ear mustard | Brassicaceae | |
| Consolida | knight's-spur | Ranunculaceae | |
| Consolida ajacis | doubtful knight's-spur | Ranunculaceae | |
| Convolvulus | bindweed | Convolvulaceae | |
| Convolvulus arvensis | field bindweed | Convolvulaceae | |
| Convolvulus equitans | Texas bindweed | Convolvulaceae | |
| Conyza | horseweed | Asteraceae | |
| Conyza bonariensis | asthmaweed | Asteraceae | |
| Conyza canadensis | Canadian horseweed | Asteraceae | |
| Conyza canadensis var. canadensis | Canadian horseweed | Asteraceae | |
| Conyza canadensis var. glabrata | Canadian horseweed | Asteraceae | |
| Conyza canadensis var. pusilla | Canadian horseweed | Asteraceae | |
| Corallorhiza | coralroot | Orchidaceae | |
| Corallorhiza maculata | summer coralroot | Orchidaceae | |
| Corallorhiza maculata var. maculata | summer coralroot | Orchidaceae | |
| Corallorhiza maculata var. occidentalis | summer coralroot | Orchidaceae | |
| Corallorhiza striata | hooded coralroot | Orchidaceae | |
| Corallorhiza striata var. vreelandii | Vreeland's coralroot | Orchidaceae | |
| Corallorhiza wisteriana | spring coralroot | Orchidaceae | |
| Corchorus | corchorus | Tiliaceae | |
| Corchorus hirtus | Orinoco jute | Tiliaceae | |
| Cordia | cordia | Boraginaceae | |
| Cordia parvifolia | small-leaf geigertree | Boraginaceae | |
| Cordylanthus | bird's-beak | Scrophulariaceae | |
| Cordylanthus laxiflorus | nodding bird's-beak | Scrophulariaceae | |
| Cordylanthus nevinii | Nevin's bird's-beak | Scrophulariaceae | |
| Cordylanthus parviflorus | purple bird's-beak | Scrophulariaceae | |
| Cordylanthus wrightii | Wright's bird's beak | Scrophulariaceae | |
| Cordylanthus wrightii ssp. kaibabensis | Kaibab bird's beak | Scrophulariaceae | |
| Cordylanthus wrightii ssp. tenuifolius | Wright's bird's beak | Scrophulariaceae | |
| Cordylanthus wrightii ssp. wrightii | Wright's bird's beak | Scrophulariaceae | |
| Coreocarpus | coreocarpus | Asteraceae | |
| Coreocarpus arizonicus | little lemonhead | Asteraceae | |
| Coreopsis | tickseed | Asteraceae | |
| Coreopsis californica | California tickseed | Asteraceae | |
| Coreopsis californica var. newberryi | Newberry's tickseed | Asteraceae | |
| Coreopsis tinctoria | golden tickseed | Asteraceae | |
| Coreopsis tinctoria var. atkinsoniana | Atkinson's tickseed | Asteraceae | |
| Coreopsis tinctoria var. tinctoria | golden tickseed | Asteraceae | |
| Coriandrum | coriander | Apiaceae | |
| Coriandrum sativum | coriander | Apiaceae | |
| Corispermum | bugseed | Chenopodiaceae | |
| Corispermum americanum | American bugseed | Chenopodiaceae | |
| Corispermum americanum var. americanum | American bugseed | Chenopodiaceae | |
| Corispermum americanum var. rydbergii | American bugseed | Chenopodiaceae | |
| Corispermum welshii | Welsh's bugseed | Chenopodiaceae | |
| Cornus | dogwood | Cornaceae | |
| Cornus sericea | redosier dogwood | Cornaceae | |
| Cornus sericea ssp. sericea | redosier dogwood | Cornaceae | |
| Coronopus | swinecress | Brassicaceae | |
| Coronopus didymus | lesser swinecress | Brassicaceae | |
| Corydalis | fumewort | Fumariaceae | |
| Corydalis aurea | scrambled eggs | Fumariaceae | |
| Corydalis curvisiliqua | curvepod fumewort | Fumariaceae | |
| Corydalis curvisiliqua ssp. occidentalis | curvepod fumewort | Fumariaceae | |
| Coryphantha | beehive cactus | Cactaceae | |
| Coryphantha recurvata | Santa Cruz beehive cactus | Cactaceae | |
| Coryphantha robustispina | long-tubercle beehive cactus | Cactaceae | |
| Coryphantha robustispina ssp. robustispina | long-tubercle beehive cactus | Cactaceae | |
| Coryphantha robustispina ssp. scheeri | Scheer's beehive cactus | Cactaceae | |
| Coryphantha robustispina ssp. uncinata | Scheer's beehive cactus | Cactaceae | |
| Cosmos | cosmos | Asteraceae | |
| Cosmos bipinnatus | garden cosmos | Asteraceae | |
| Cosmos parviflorus | southwestern cosmos | Asteraceae | |
| Cottea | cotta grass | Poaceae | |
| Cottea pappophoroides | cotta grass | Poaceae | |
| Cotula | waterbuttons | Asteraceae | |
| Cotula australis | Australian waterbuttons | Asteraceae | |
| Cotula coronopifolia | common brassbuttons | Asteraceae | |
| Coursetia | babybonnets | Fabaceae | |
| Coursetia caribaea | anil falso | Fabaceae | |
| Coursetia caribaea var. sericea | anil falso | Fabaceae | |
| Coursetia glabella | smooth babybonnets | Fabaceae | |
| Coursetia glandulosa | rosary babybonnets | Fabaceae | |
| Crassula | pygmyweed | Crassulaceae | |
| Crassula aquatica | water pygmyweed | Crassulaceae | |
| Crassula connata | sand pygmyweed | Crassulaceae | |
| Crassula connata var. erectoides | sand pygmyweed | Crassulaceae | |
| Crassula connata var. eremica | sand pygmyweed | Crassulaceae | |
| Crassula connata var. subsimplex | sand pygmyweed | Crassulaceae | |
| Crassula viridis | pricklyseed pygmyweed | Crassulaceae | |
| Crataegus | hawthorn | Rosaceae | |
| Crataegus erythropoda | cerro hawthorn | Rosaceae | |
| Crataegus rivularis | river hawthorn | Rosaceae | |
| Crataegus succulenta | fleshy hawthorn | Rosaceae | |
| Crepis | hawksbeard | Asteraceae | |
| Crepis acuminata | tapertip hawksbeard | Asteraceae | |
| Crepis acuminata ssp. acuminata | tapertip hawksbeard | Asteraceae | |
| Crepis intermedia | limestone hawksbeard | Asteraceae | |
| Crepis occidentalis | largeflower hawksbeard | Asteraceae | |
| Crepis occidentalis ssp. costata | largeflower hawksbeard | Asteraceae | |
| Crepis occidentalis ssp. occidentalis | largeflower hawksbeard | Asteraceae | |
| Crepis runcinata | fiddleleaf hawksbeard | Asteraceae | |
| Crepis runcinata ssp. barberi | Barber's hawksbeard | Asteraceae | |
| Crepis runcinata ssp. glauca | fiddleleaf hawksbeard | Asteraceae | |
| Cressa | alkaliweed | Convolvulaceae | |
| Cressa truxillensis | spreading alkaliweed | Convolvulaceae | |
| Crossosoma | rockflower | Crossosomataceae | |
| Crossosoma bigelovii | ragged rockflower | Crossosomataceae | |
| Crossosoma bigelovii var. bigelovii | ragged rockflower | Crossosomataceae | |
| Crossosoma bigelovii var. glaucum | ragged rockflower | Crossosomataceae | |
| Crotalaria | rattlebox | Fabaceae | |
| Crotalaria pumila | low rattlebox | Fabaceae | |
| Crotalaria sagittalis | arrowhead rattlebox | Fabaceae | |
| Croton | croton | Euphorbiaceae | |
| Croton californicus | California croton | Euphorbiaceae | |
| Croton californicus var. californicus | California croton | Euphorbiaceae | |
| Croton californicus var. tenuis | California croton | Euphorbiaceae | |
| Croton ciliatoglandulifer | Mexican croton | Euphorbiaceae | |
| Croton fruticulosus | bush croton | Euphorbiaceae | |
| Croton lindheimerianus | threeseed croton | Euphorbiaceae | |
| Croton lindheimerianus var. lindheimerianus | threeseed croton | Euphorbiaceae | |
| Croton lindheimerianus var. tharpii | Tharp's croton | Euphorbiaceae | |
| Croton monanthogynus | prairie tea | Euphorbiaceae | |
| Croton pottsii | leatherweed | Euphorbiaceae | |
| Croton pottsii var. pottsii | leatherweed | Euphorbiaceae | |
| Croton setigerus | dove weed | Euphorbiaceae | |
| Croton sonorae | Sonoran croton | Euphorbiaceae | |
| Croton texensis | Texas croton | Euphorbiaceae | |
| Croton texensis var. texensis | Texas croton | Euphorbiaceae | |
| Croton texensis var. utahensis | Utah croton | Euphorbiaceae | |
| Croton wigginsii | Wiggins' croton | Euphorbiaceae | |
| Crusea | mountain saucerflower | Rubiaceae | |
| Crusea diversifolia | mountain saucerflower | Rubiaceae | |
| Crypsis | pricklegrass | Poaceae | |
| Crypsis schoenoides | swamp pricklegrass | Poaceae | |
| Cryptantha | cryptantha | Boraginaceae | |
| Cryptantha abata | dentnut cryptantha | Boraginaceae | |
| Cryptantha albida | New Mexico cryptantha | Boraginaceae | |
| Cryptantha angustifolia | Panamint cryptantha | Boraginaceae | |
| Cryptantha atwoodii | Atwood's cryptantha | Boraginaceae | |
| Cryptantha bakeri | Baker's cryptantha | Boraginaceae | |
| Cryptantha barbigera | bearded cryptantha | Boraginaceae | |
| Cryptantha capitata | capitate cryptantha | Boraginaceae | |
| Cryptantha cinerea | James' cryptantha | Boraginaceae | |
| Cryptantha cinerea var. arenicola | James' cryptantha | Boraginaceae | |
| Cryptantha cinerea var. cinerea | James' cryptantha | Boraginaceae | |
| Cryptantha cinerea var. jamesii | James' cryptantha | Boraginaceae | |
| Cryptantha cinerea var. pustulosa | James' cryptantha | Boraginaceae | |
| Cryptantha circumscissa | cushion cryptantha | Boraginaceae | |
| Cryptantha circumscissa var. circumscissa | cushion cryptantha | Boraginaceae | |
| Cryptantha confertiflora | basin yellow cryptantha | Boraginaceae | |
| Cryptantha costata | ribbed cryptantha | Boraginaceae | |
| Cryptantha crassisepala | thicksepal cryptantha | Boraginaceae | |
| Cryptantha crassisepala var. elachantha | thicksepal cryptantha | Boraginaceae | |
| Cryptantha decipiens | gravelbar cryptantha | Boraginaceae | |
| Cryptantha dumetorum | bushloving cryptantha | Boraginaceae | |
| Cryptantha fendleri | sanddune cryptantha | Boraginaceae | |
| Cryptantha flava | Brenda's yellow cryptantha | Boraginaceae | |
| Cryptantha flavoculata | roughseed cryptantha | Boraginaceae | |
| Cryptantha fulvocanescens | tawny cryptantha | Boraginaceae | |
| Cryptantha fulvocanescens var. fulvocanescens | tawny cryptantha | Boraginaceae | |
| Cryptantha fulvocanescens var. nitida | tawny cryptantha | Boraginaceae | |
| Cryptantha ganderi | Gander's cryptantha | Boraginaceae | |
| Cryptantha gracilis | narrowstem cryptantha | Boraginaceae | |
| Cryptantha holoptera | winged cryptantha | Boraginaceae | |
| Cryptantha humilis | roundspike cryptantha | Boraginaceae | |
| Cryptantha intermedia | Clearwater cryptantha | Boraginaceae | |
| Cryptantha maritima | Guadalupe cryptantha | Boraginaceae | |
| Cryptantha maritima var. maritima | Guadalupe cryptantha | Boraginaceae | |
| Cryptantha maritima var. pilosa | Guadalupe cryptantha | Boraginaceae | |
| Cryptantha micrantha | redroot cryptantha | Boraginaceae | |
| Cryptantha micrantha var. micrantha | redroot cryptantha | Boraginaceae | |
| Cryptantha muricata | pointed cryptantha | Boraginaceae | |
| Cryptantha nevadensis | Nevada cryptantha | Boraginaceae | |
| Cryptantha nevadensis var. nevadensis | Nevada cryptantha | Boraginaceae | |
| Cryptantha nevadensis var. rigida | Nevada cryptantha | Boraginaceae | |
| Cryptantha osterhoutii | Osterhout's cryptantha | Boraginaceae | |
| Cryptantha pterocarya | wingnut cryptantha | Boraginaceae | |
| Cryptantha pterocarya var. cycloptera | wingnut cryptantha | Boraginaceae | |
| Cryptantha pterocarya var. pterocarya | wingnut cryptantha | Boraginaceae | |
| Cryptantha pterocarya var. stenoloba | wingnut cryptantha | Boraginaceae | |
| Cryptantha pusilla | low cryptantha | Boraginaceae | |
| Cryptantha racemosa | bushy cryptantha | Boraginaceae | |
| Cryptantha recurvata | curvenut cryptantha | Boraginaceae | |
| Cryptantha semiglabra | smooth cryptantha | Boraginaceae | |
| Cryptantha setosissima | bristly cryptantha | Boraginaceae | |
| Cryptantha utahensis | scented cryptantha | Boraginaceae | |
| Cryptantha virginensis | Virgin River cryptantha | Boraginaceae | |
| Cryptogramma | rockbrake | Pteridaceae | |
| Cryptogramma acrostichoides | American rockbrake | Pteridaceae | |
| Cucurbita | gourd | Cucurbitaceae | |
| Cucurbita digitata | fingerleaf gourd | Cucurbitaceae | |
| Cucurbita foetidissima | Missouri gourd | Cucurbitaceae | |
| Cucurbita palmata | coyote gourd | Cucurbitaceae | |
| Cuphea | waxweed | Lythraceae | |
| Cuphea wrightii | Wright's waxweed | Lythraceae | |
| Cupressus | cypress | Cupressaceae | |
| Cupressus arizonica | Arizona cypress | Cupressaceae | |
| Cupressus arizonica ssp. arizonica | Arizona cypress | Cupressaceae | |
| Cuscuta | dodder | Cuscutaceae | |
| Cuscuta applanata | Gila River dodder | Cuscutaceae | |
| Cuscuta californica | chaparral dodder | Cuscutaceae | |
| Cuscuta californica var. californica | chaparral dodder | Cuscutaceae | |
| Cuscuta cephalanthi | buttonbush dodder | Cuscutaceae | |
| Cuscuta coryli | hazel dodder | Cuscutaceae | |
| Cuscuta dentatasquamata | los pinitos dodder | Cuscutaceae | |
| Cuscuta denticulata | desert dodder | Cuscutaceae | |
| Cuscuta denticulata var. denticulata | desert dodder | Cuscutaceae | |
| Cuscuta erosa | Sonoran dodder | Cuscutaceae | |
| Cuscuta gronovii | scaldweed | Cuscutaceae | |
| Cuscuta gronovii var. gronovii | scaldweed | Cuscutaceae | |
| Cuscuta indecora | bigseed alfalfa dodder | Cuscutaceae | |
| Cuscuta indecora var. indecora | bigseed alfalfa dodder | Cuscutaceae | |
| Cuscuta indecora var. neuropetala | bigseed dodder | Cuscutaceae | |
| Cuscuta mitriformis | Cochise dodder | Cuscutaceae | |
| Cuscuta odontolepis | Santa Rita Mountain dodder | Cuscutaceae | |
| Cuscuta pentagona | fiveangled dodder | Cuscutaceae | |
| Cuscuta pentagona var. pentagona | fiveangled dodder | Cuscutaceae | |
| Cuscuta potosina | globe dodder | Cuscutaceae | |
| Cuscuta potosina var. globifera | globe dodder | Cuscutaceae | |
| Cuscuta salina | saltmarsh dodder | Cuscutaceae | |
| Cuscuta salina var. papillata | goldenthread | Cuscutaceae | |
| Cuscuta salina var. salina | saltmarsh dodder | Cuscutaceae | |
| Cuscuta tuberculata | tubercle dodder | Cuscutaceae | |
| Cuscuta umbellata | flatglobe dodder | Cuscutaceae | |
| Cuscuta warneri | Warner's dodder | Cuscutaceae | |
| Cyclachaena | Asteraceae | ||
| Cyclachaena xanthifolia | giant sumpweed | Asteraceae | |
| Cycladenia | waxydogbane | Apocynaceae | |
| Cycladenia humilis | Sacramento waxydogbane | Apocynaceae | |
| Cycladenia humilis var. jonesii | Jones' waxydogbane | Apocynaceae | |
| Cyclanthera | cyclanthera | Cucurbitaceae | |
| Cyclanthera dissecta | cutleaf cyclanthera | Cucurbitaceae | |
| Cycloloma | cycloloma | Chenopodiaceae | |
| Cycloloma atriplicifolium | winged pigweed | Chenopodiaceae | |
| Cyclospermum | marsh parsley | Apiaceae | |
| Cyclospermum leptophyllum | marsh parsley | Apiaceae | |
| Cylindropuntia | Cactaceae | ||
| Cylindropuntia abysii | Peach Springs canyon cholla | Cactaceae | |
| Cylindropuntia acanthocarpa | buck-horn cholla | Cactaceae | |
| Cylindropuntia acanthocarpa var. acanthocarpa | buckhorn cholla | Cactaceae | |
| Cylindropuntia acanthocarpa var. coloradensis | Colorado buckhorn cholla | Cactaceae | |
| Cylindropuntia acanthocarpa var. major | buckhorn cholla | Cactaceae | |
| Cylindropuntia acanthocarpa var. thornberi | Thornber's buckhorn cholla | Cactaceae | |
| Cylindropuntia arbuscula | Arizona pencil cholla | Cactaceae | |
| Cylindropuntia bigelovii | teddybear cholla | Cactaceae | |
| Cylindropuntia congesta | Cactaceae | ||
| Cylindropuntia echinocarpa | Wiggins' cholla | Cactaceae | |
| Cylindropuntia fulgida | jumping cholla | Cactaceae | |
| Cylindropuntia fulgida var. fulgida | jumping cholla | Cactaceae | |
| Cylindropuntia fulgida var. mamillata | jumping cholla | Cactaceae | |
| Cylindropuntia imbricata | tree cholla | Cactaceae | |
| Cylindropuntia imbricata var. imbricata | tree cholla | Cactaceae | |
| Cylindropuntia kelvinensis | Cactaceae | ||
| Cylindropuntia leptocaulis | Christmas cactus | Cactaceae | |
| Cylindropuntia multigeniculata | Blue Diamond cholla | Cactaceae | |
| Cylindropuntia ramosissima | branched pencil cholla | Cactaceae | |
| Cylindropuntia spinosior | walkingstick cactus | Cactaceae | |
| Cylindropuntia tetracantha | Tucson pricklypear | Cactaceae | |
| Cylindropuntia versicolor | staghorn cholla | Cactaceae | |
| Cylindropuntia vivipara | Cactaceae | ||
| Cylindropuntia whipplei | Whipple cholla | Cactaceae | |
| Cymopterus | springparsley | Apiaceae | |
| Cymopterus acaulis | plains springparsley | Apiaceae | |
| Cymopterus acaulis var. fendleri | Fendler's springparsley | Apiaceae | |
| Cymopterus beckii | featherleaf springparsley | Apiaceae | |
| Cymopterus bulbosus | bulbous springparsley | Apiaceae | |
| Cymopterus constancei | Constance's springparsley | Apiaceae | |
| Cymopterus jonesii | Jones' springparsley | Apiaceae | |
| Cymopterus megacephalus | largeleaf springparsley | Apiaceae | |
| Cymopterus multinervatus | purplenerve springparsley | Apiaceae | |
| Cymopterus newberryi | sweetroot springparsley | Apiaceae | |
| Cymopterus purpurascens | widewing springparsley | Apiaceae | |
| Cymopterus purpureus | purple springparsley | Apiaceae | |
| Cynanchum | swallow-wort | Asclepiadaceae | |
| Cynanchum arizonicum | Arizona swallow-wort | Asclepiadaceae | |
| Cynanchum ligulatum | Mexican swallow-wort | Asclepiadaceae | |
| Cynanchum utahense | Utah swallow-wort | Asclepiadaceae | |
| Cynanchum wigginsii | Wiggins' swallow-wort | Asclepiadaceae | |
| Cynara | cynara | Asteraceae | |
| Cynara scolymus | globe artichoke | Asteraceae | |
| Cynodon | Bermudagrass | Poaceae | |
| Cynodon dactylon | Bermudagrass | Poaceae | |
| Cynoglossum | hound's tongue | Boraginaceae | |
| Cynoglossum officinale | gypsyflower | Boraginaceae | |
| Cyperus | flatsedge | Cyperaceae | |
| Cyperus acuminatus | tapertip flatsedge | Cyperaceae | |
| Cyperus aggregatus | inflatedscale flatsedge | Cyperaceae | |
| Cyperus amabilis | foothill flatsedge | Cyperaceae | |
| Cyperus dentoniae | hairy flatsedge | Cyperaceae | |
| Cyperus difformis | variable flatsedge | Cyperaceae | |
| Cyperus dipsaceus | Wright's flatsedge | Cyperaceae | |
| Cyperus erythrorhizos | redroot flatsedge | Cyperaceae | |
| Cyperus esculentus | yellow nutsedge | Cyperaceae | |
| Cyperus esculentus var. leptostachyus | yellow nutsedge | Cyperaceae | |
| Cyperus fendlerianus | Fendler's flatsedge | Cyperaceae | |
| Cyperus flavicomus | whiteedge flatsedge | Cyperaceae | |
| Cyperus hermaphroditus | hermaphrodite flatsedge | Cyperaceae | |
| Cyperus hypopitys | pine flatsedge | Cyperaceae | |
| Cyperus involucratus | unbrella plant | Cyperaceae | |
| Cyperus laevigatus | smooth flatsedge | Cyperaceae | |
| Cyperus manimae | spectacular flatsedge | Cyperaceae | |
| Cyperus manimae var. asperrimus | spectacular flatsedge | Cyperaceae | |
| Cyperus mutisii | Mutis' flatsedge | Cyperaceae | |
| Cyperus niger | black flatsedge | Cyperaceae | |
| Cyperus odoratus | fragrant flatsedge | Cyperaceae | |
| Cyperus pallidicolor | pallid flatsedge | Cyperaceae | |
| Cyperus parishii | Parish's flatsedge | Cyperaceae | |
| Cyperus retroflexus | oneflower flatsedge | Cyperaceae | |
| Cyperus rotundus | nutgrass | Cyperaceae | |
| Cyperus schweinitzii | Schweinitz's flatsedge | Cyperaceae | |
| Cyperus seslerioides | Texas flatsedge | Cyperaceae | |
| Cyperus spectabilis | spectacular flatsedge | Cyperaceae | |
| Cyperus sphaerolepis | Rusby's flatsedge | Cyperaceae | |
| Cyperus squarrosus | bearded flatsedge | Cyperaceae | |
| Cyperus strigosus | strawcolored flatsedge | Cyperaceae | |
| Cyperus tetragonus | fourangle flatsedge | Cyperaceae | |
| Cypripedium | lady's slipper | Orchidaceae | |
| Cypripedium parviflorum | lesser yellow lady's slipper | Orchidaceae | |
| Cypripedium parviflorum var. pubescens | greater yellow lady's slipper | Orchidaceae | |
| Cypselea | cypselea | Aizoaceae | |
| Cypselea humifusa | panal | Aizoaceae | |
| Cystopteris | bladderfern | Dryopteridaceae | |
| Cystopteris bulbifera | bulblet bladderfern | Dryopteridaceae | |
| Cystopteris fragilis | brittle bladderfern | Dryopteridaceae | |
| Cystopteris reevesiana | Reeves' bladderfern | Dryopteridaceae | |
| Cystopteris tenuis | upland brittle bladderfern | Dryopteridaceae | |
| Cystopteris utahensis | Utah bladderfern | Dryopteridaceae | |
| D | |||
| Dactylis | orchardgrass | Poaceae | |
| Dactylis glomerata | orchardgrass | Poaceae | |
| Dactylis glomerata ssp. glomerata | orchardgrass | Poaceae | |
| Dactyloctenium | crowfoot grass | Poaceae | |
| Dactyloctenium aegyptium | Egyptian grass | Poaceae | |
| Dactyloctenium radulans | buttongrass | Poaceae | |
| Dactylorhiza | keyflower | Orchidaceae | |
| Dactylorhiza viridis | longbract frog orchid | Orchidaceae | |
| Dalea | prairie clover | Fabaceae | |
| Dalea albiflora | whiteflower prairie clover | Fabaceae | |
| Dalea aurea | golden prairie clover | Fabaceae | |
| Dalea bicolor | silver prairie clover | Fabaceae | |
| Dalea bicolor var. argyrea | silver prairie clover | Fabaceae | |
| Dalea brachystachya | Fort Bowie prairie clover | Fabaceae | |
| Dalea candida | white prairie clover | Fabaceae | |
| Dalea candida var. oligophylla | white prairie clover | Fabaceae | |
| Dalea exigua | Chihuahuan prairie clover | Fabaceae | |
| Dalea exserta | Mexican prairie clover | Fabaceae | |
| Dalea filiformis | Sonoran prairie clover | Fabaceae | |
| Dalea flavescens | Canyonlands prairie clover | Fabaceae | |
| Dalea formosa | featherplume | Fabaceae | |
| Dalea grayi | Gray's prairie clover | Fabaceae | |
| Dalea jamesii | James' prairie clover | Fabaceae | |
| Dalea lachnostachys | glandleaf prairie clover | Fabaceae | |
| Dalea lanata | woolly prairie clover | Fabaceae | |
| Dalea lanata var. terminalis | woolly prairie clover | Fabaceae | |
| Dalea leporina | foxtail prairie clover | Fabaceae | |
| Dalea lumholtzii | Lumholtz's prairie clover | Fabaceae | |
| Dalea mollis | hairy prairie clover | Fabaceae | |
| Dalea mollissima | soft prairie clover | Fabaceae | |
| Dalea nana | dwarf prairie clover | Fabaceae | |
| Dalea nana var. carnescens | dwarf prairie clover | Fabaceae | |
| Dalea nana var. nana | dwarf prairie clover | Fabaceae | |
| Dalea neomexicana | downy prairie clover | Fabaceae | |
| Dalea neomexicana var. neomexicana | downy prairie clover | Fabaceae | |
| Dalea pogonathera | bearded prairie clover | Fabaceae | |
| Dalea pogonathera var. pogonathera | bearded prairie clover | Fabaceae | |
| Dalea polygonoides | sixweeks prairie clover | Fabaceae | |
| Dalea pringlei | Pringle's prairie clover | Fabaceae | |
| Dalea pulchra | Santa Catalina prairie clover | Fabaceae | |
| Dalea purpurea | purple prairie clover | Fabaceae | |
| Dalea purpurea var. purpurea | purple prairie clover | Fabaceae | |
| Dalea searlsiae | Searls' prairie clover | Fabaceae | |
| Dalea tentaculoides | Gentry's indigobush | Fabaceae | |
| Dalea tenuifolia | slimleaf prairie clover | Fabaceae | |
| Dalea urceolata | pineforest prairie clover | Fabaceae | |
| Dalea versicolor | oakwoods prairie clover | Fabaceae | |
| Dalea versicolor var. sessilis | oakwoods prairie clover | Fabaceae | |
| Dalea versicolor var. versicolor | oakwoods prairie clover | Fabaceae | |
| Dalea wrightii | Wright's prairie clover | Fabaceae | |
| Danthonia | oatgrass | Poaceae | |
| Danthonia californica | California oatgrass | Poaceae | |
| Danthonia intermedia | timber oatgrass | Poaceae | |
| Danthonia spicata | poverty oatgrass | Poaceae | |
| Dasiphora | shrubby cinquefoil | Rosaceae | |
| Dasiphora fruticosa | shrubby cinquefoil | Rosaceae | |
| Dasiphora fruticosa ssp. floribunda | shrubby cinquefoil | Rosaceae | |
| Dasylirion | sotol | Liliaceae | |
| Dasylirion wheeleri | common sotol | Liliaceae | |
| Dasyochloa | woollygrass | Poaceae | |
| Dasyochloa pulchella | low woollygrass | Poaceae | |
| Datura | jimsonweed | Solanaceae | |
| Datura discolor | desert thorn-apple | Solanaceae | |
| Datura inoxia | pricklyburr | Solanaceae | |
| Datura quercifolia | Chinese thorn-apple | Solanaceae | |
| Datura stramonium | jimsonweed | Solanaceae | |
| Datura wrightii | sacred thorn-apple | Solanaceae | |
| Daucus | wild carrot | Apiaceae | |
| Daucus carota | Queen Anne's lace | Apiaceae | |
| Daucus pusillus | American wild carrot | Apiaceae | |
| Delphinium | larkspur | Ranunculaceae | |
| Delphinium andesicola | Chiricahua Mountain larkspur | Ranunculaceae | |
| Delphinium barbeyi | subalpine larkspur | Ranunculaceae | |
| Delphinium confertiflorum | Ranunculaceae | ||
| Delphinium geraniifolium | Clark Valley larkspur | Ranunculaceae | |
| Delphinium glaucum | Sierra larkspur | Ranunculaceae | |
| Delphinium nuttallianum | twolobe larkspur | Ranunculaceae | |
| Delphinium parishii | desert larkspur | Ranunculaceae | |
| Delphinium parishii ssp. parishii | Parish's larkspur | Ranunculaceae | |
| Delphinium scaposum | tall mountain larkspur | Ranunculaceae | |
| Delphinium scopulorum | Rocky Mountain larkspur | Ranunculaceae | |
| Delphinium wootonii | Organ Mountain larkspur | Ranunculaceae | |
| Deschampsia | hairgrass | Poaceae | |
| Deschampsia cespitosa | tufted hairgrass | Poaceae | |
| Deschampsia danthonioides | annual hairgrass | Poaceae | |
| Deschampsia elongata | slender hairgrass | Poaceae | |
| Descurainia | tansymustard | Brassicaceae | |
| Descurainia californica | Sierra tansymustard | Brassicaceae | |
| Descurainia incana | mountain tansymustard | Brassicaceae | |
| Descurainia incana ssp. incisa | mountain tansymustard | Brassicaceae | |
| Descurainia incana ssp. viscosa | mountain tansymustard | Brassicaceae | |
| Descurainia obtusa | blunt tansymustard | Brassicaceae | |
| Descurainia obtusa ssp. adenophora | blunt tansymustard | Brassicaceae | |
| Descurainia obtusa ssp. obtusa | blunt tansymustard | Brassicaceae | |
| Descurainia pinnata | western tansymustard | Brassicaceae | |
| Descurainia pinnata ssp. filipes | western tansymustard | Brassicaceae | |
| Descurainia pinnata ssp. glabra | western tansymustard | Brassicaceae | |
| Descurainia pinnata ssp. halictorum | western tansymustard | Brassicaceae | |
| Descurainia pinnata ssp. ochroleuca | western tansymustard | Brassicaceae | |
| Descurainia pinnata ssp. paysonii | Payson's tansymustard | Brassicaceae | |
| Descurainia sophia | herb sophia | Brassicaceae | |
| Desmanthus | bundleflower | Fabaceae | |
| Desmanthus bicornutus | two-horn bundleflower | Fabaceae | |
| Desmanthus cooleyi | Cooley's bundleflower | Fabaceae | |
| Desmanthus covillei | Coville's bundleflower | Fabaceae | |
| Desmanthus glandulosus | glandular bundleflower | Fabaceae | |
| Desmodium | ticktrefoil | Fabaceae | |
| Desmodium arizonicum | Arizona ticktrefoil | Fabaceae | |
| Desmodium batocaulon | San Pedro ticktrefoil | Fabaceae | |
| Desmodium cinerascens | spiked ticktrefoil | Fabaceae | |
| Desmodium grahamii | Graham's ticktrefoil | Fabaceae | |
| Desmodium gramineum | grassleaf ticktrefoil | Fabaceae | |
| Desmodium intortum | greenleaf ticktrefoil | Fabaceae | |
| Desmodium metcalfei | Metcalfe's ticktrefoil | Fabaceae | |
| Desmodium neomexicanum | New Mexico ticktrefoil | Fabaceae | |
| Desmodium procumbens | western trailing ticktrefoil | Fabaceae | |
| Desmodium procumbens var. exiguum | western trailing ticktrefoil | Fabaceae | |
| Desmodium psilocarpum | Santa Cruz Island ticktrefoil | Fabaceae | |
| Desmodium psilophyllum | simpleleaf ticktrefoil | Fabaceae | |
| Desmodium retinens | Santa Rita Mountain ticktrefoil | Fabaceae | |
| Desmodium rosei | Rose's ticktrefoil | Fabaceae | |
| Desmodium scopulorum | Sonoran ticktrefoil | Fabaceae | |
| Dichanthelium | rosette grass | Poaceae | |
| Dichanthelium acuminatum | tapered rosette grass | Poaceae | |
| Dichanthelium acuminatum var. acuminatum | tapered rosette grass | Poaceae | |
| Dichanthelium acuminatum var. fasciculatum | western panicgrass | Poaceae | |
| Dichanthelium oligosanthes | Heller's rosette grass | Poaceae | |
| Dichanthelium oligosanthes var. scribnerianum | Scribner's rosette grass | Poaceae | |
| Dichelostemma | snakelily | Liliaceae | |
| Dichelostemma capitatum | bluedicks | Liliaceae | |
| Dichelostemma capitatum ssp. capitatum | bluedicks | Liliaceae | |
| Dichelostemma capitatum ssp. pauciflorum | bluedicks | Liliaceae | |
| Dichondra | ponysfoot | Convolvulaceae | |
| Dichondra argentea | silver ponysfoot | Convolvulaceae | |
| Dichondra brachypoda | New Mexico ponysfoot | Convolvulaceae | |
| Dichondra micrantha | Asian ponysfoot | Convolvulaceae | |
| Dichondra sericea | silverleaf ponysfoot | Convolvulaceae | |
| Dicliptera | foldwing | Acanthaceae | |
| Dicliptera resupinata | Arizona foldwing | Acanthaceae | |
| Dicoria | twinbugs | Asteraceae | |
| Dicoria canescens | desert twinbugs | Asteraceae | |
| Dicoria canescens ssp. brandegeei | desert twinbugs | Asteraceae | |
| Dicoria canescens ssp. canescens | desert twinbugs | Asteraceae | |
| Digitaria | crabgrass | Poaceae | |
| Digitaria californica | Arizona cottontop | Poaceae | |
| Digitaria ciliaris | southern crabgrass | Poaceae | |
| Digitaria eriantha | digitgrass | Poaceae | |
| Digitaria insularis | sourgrass | Poaceae | |
| Digitaria ischaemum | smooth crabgrass | Poaceae | |
| Digitaria pubiflora | Carolina crabgrass | Poaceae | |
| Digitaria sanguinalis | hairy crabgrass | Poaceae | |
| Dimorphocarpa | spectaclepod | Brassicaceae | |
| Dimorphocarpa pinnatifida | tansy spectaclepod | Brassicaceae | |
| Dimorphocarpa wislizeni | touristplant | Brassicaceae | |
| Dimorphotheca | Cape marigold | Asteraceae | |
| Dimorphotheca sinuata | glandular Cape marigold | Asteraceae | |
| Diodia | buttonweed | Rubiaceae | |
| Diodia teres | poorjoe | Rubiaceae | |
| Diodia teres var. angustata | poorjoe | Rubiaceae | |
| Diodia teres var. teres | poorjoe | Rubiaceae | |
| Diphysa | diphysa | Fabaceae | |
| Diphysa thurberi | Thurber's diphysa | Fabaceae | |
| Diplotaxis | wallrocket | Brassicaceae | |
| Diplotaxis muralis | annual wallrocket | Brassicaceae | |
| Diplotaxis tenuifolia | perennial wallrocket | Brassicaceae | |
| Dipsacus | teasel | Dipsacaceae | |
| Dipsacus fullonum | Fuller's teasel | Dipsacaceae | |
| Distichlis | saltgrass | Poaceae | |
| Distichlis spicata | saltgrass | Poaceae | |
| Dithyrea | shieldpod | Brassicaceae | |
| Dithyrea californica | California shieldpod | Brassicaceae | |
| Dodecatheon | shootingstar | Primulaceae | |
| Dodecatheon alpinum | alpine shootingstar | Primulaceae | |
| Dodecatheon alpinum ssp. majus | alpine shootingstar | Primulaceae | |
| Dodecatheon dentatum | white shootingstar | Primulaceae | |
| Dodecatheon dentatum ssp. ellisiae | Ellis' shootingstar | Primulaceae | |
| Dodecatheon pulchellum | darkthroat shootingstar | Primulaceae | |
| Dodecatheon pulchellum ssp. pulchellum | darkthroat shootingstar | Primulaceae | |
| Dodonaea | dodonaea | Sapindaceae | |
| Dodonaea viscosa | Florida hopbush | Sapindaceae | |
| Draba | draba | Brassicaceae | |
| Draba albertina | slender draba | Brassicaceae | |
| Draba asprella | rough draba | Brassicaceae | |
| Draba asprella var. asprella | rough draba | Brassicaceae | |
| Draba asprella var. kaibabensis | Kaibab draba | Brassicaceae | |
| Draba asprella var. stelligera | rough draba | Brassicaceae | |
| Draba aurea | golden draba | Brassicaceae | |
| Draba brachycarpa | shortpod draba | Brassicaceae | |
| Draba crassifolia | snowbed draba | Brassicaceae | |
| Draba cuneifolia | wedgeleaf draba | Brassicaceae | |
| Draba cuneifolia var. cuneifolia | wedgeleaf draba | Brassicaceae | |
| Draba cuneifolia var. integrifolia | wedgeleaf draba | Brassicaceae | |
| Draba cuneifolia var. sonorae | Sonora draba | Brassicaceae | |
| Draba helleriana | Heller's draba | Brassicaceae | |
| Draba helleriana var. bifurcata | Heller's draba | Brassicaceae | |
| Draba helleriana var. blumeri | Blumer's draba | Brassicaceae | |
| Draba helleriana var. patens | Heller's draba | Brassicaceae | |
| Draba nemorosa | woodland draba | Brassicaceae | |
| Draba petrophila | Santa Rita Mountain draba | Brassicaceae | |
| Draba petrophila var. petrophila | Santa Rita Mountain draba | Brassicaceae | |
| Draba petrophila var. viridis | Santa Rita Mountain draba | Brassicaceae | |
| Draba platycarpa | broadpod draba | Brassicaceae | |
| Draba rectifructa | mountain draba | Brassicaceae | |
| Draba reptans | Carolina draba | Brassicaceae | |
| Draba spectabilis | showy draba | Brassicaceae | |
| Draba spectabilis var. spectabilis | showy draba | Brassicaceae | |
| Draba standleyi | Standley's draba | Brassicaceae | |
| Dracocephalum | dragonhead | Lamiaceae | |
| Dracocephalum parviflorum | American dragonhead | Lamiaceae | |
| Drymaria | drymary | Caryophyllaceae | |
| Drymaria effusa | pinewoods drymary | Caryophyllaceae | |
| Drymaria effusa var. depressa | pinewoods drymary | Caryophyllaceae | |
| Drymaria effusa var. effusa | pinewoods drymary | Caryophyllaceae | |
| Drymaria glandulosa | Fendler's drymary | Caryophyllaceae | |
| Drymaria leptophylla | canyon drymary | Caryophyllaceae | |
| Drymaria molluginea | slimleaf drymary | Caryophyllaceae | |
| Drymaria pachyphylla | thickleaf drymary | Caryophyllaceae | |
| Drymaria viscosa | sticky drymary | Caryophyllaceae | |
| Dryopetalon | dryopetalon | Brassicaceae | |
| Dryopetalon runcinatum | rockmustard | Brassicaceae | |
| Dryopteris | woodfern | Dryopteridaceae | |
| Dryopteris arguta | coastal woodfern | Dryopteridaceae | |
| Dryopteris cinnamomea | cinnamon woodfern | Dryopteridaceae | |
| Dryopteris filix-mas | male fern | Dryopteridaceae | |
| Dryopteris rossii | Ross' woodfern | Dryopteridaceae | |
| Dudleya | dudleya | Crassulaceae | |
| Dudleya collomiae | Gila County liveforever | Crassulaceae | |
| Dudleya pulverulenta | chalk dudleya | Crassulaceae | |
| Dudleya pulverulenta ssp. arizonica | chalk dudleya | Crassulaceae | |
| Duranta | duranta | Verbenaceae | |
| Duranta erecta | golden dewdrops | Verbenaceae | |
| Dyschoriste | snakeherb | Acanthaceae | |
| Dyschoriste schiedeana | Schied's snakeherb | Acanthaceae | |
| Dyschoriste schiedeana var. decumbens | spreading snakeherb | Acanthaceae | |
| Dyssodia | dyssodia | Asteraceae | |
| Dyssodia papposa | fetid marigold | Asteraceae | |
| E | |||
| Echeandia | echeandia | Liliaceae | |
| Echeandia flavescens | Torrey's craglily | Liliaceae | |
| Echinocactus | echinocactus | Cactaceae | |
| Echinocactus horizonthalonius | devilshead | Cactaceae | |
| Echinocactus horizonthalonius var. horizonthalonius | devilshead | Cactaceae | |
| Echinocactus horizonthalonius var. nicholii | Nichol's echinocactus | Cactaceae | |
| Echinocactus polycephalus | cottontop cactus | Cactaceae | |
| Echinocactus polycephalus var. polycephalus | cottontop cactus | Cactaceae | |
| Echinocactus polycephalus var. xeranthemoides | cottontop cactus | Cactaceae | |
| Echinocereus | hedgehog cactus | Cactaceae | |
| Echinocereus apachensis | Apache hedgehog cactus | Cactaceae | |
| Echinocereus bonkerae | pinkflower hedgehog cactus | Cactaceae | |
| Echinocereus boyce-thompsonii | Boyce Thompson hedgehog cactus | Cactaceae | |
| Echinocereus coccineus | scarlet hedgehog cactus | Cactaceae | |
| Echinocereus coccineus var. arizonicus | Arizona hedgehog cactus | Cactaceae | |
| Echinocereus coccineus var. coccineus | scarlet hedgehog cactus | Cactaceae | |
| Echinocereus dasyacanthus | spiny hedgehog cactus | Cactaceae | |
| Echinocereus engelmannii | Engelmann's hedgehog cactus | Cactaceae | |
| Echinocereus engelmannii var. acicularis | Engelmann's hedgehog cactus | Cactaceae | |
| Echinocereus engelmannii var. chrysocentrus | Engelmann's hedgehog cactus | Cactaceae | |
| Echinocereus engelmannii var. engelmannii | Engelmann's hedgehog cactus | Cactaceae | |
| Echinocereus engelmannii var. variegatus | Engelmann's hedgehog cactus | Cactaceae | |
| Echinocereus fasciculatus | pinkflower hedgehog cactus | Cactaceae | |
| Echinocereus fendleri | pinkflower hedgehog cactus | Cactaceae | |
| Echinocereus fendleri ssp. fendleri | pinkflower hedgehog cactus | Cactaceae | |
| Echinocereus fendleri ssp. rectispinus | pinkflower hedgehog cactus | Cactaceae | |
| Echinocereus ledingii | Leding's hedgehog cactus | Cactaceae | |
| Echinocereus mojavensis | Mojave kingcup cactus | Cactaceae | |
| Echinocereus nicholii | Nichol's hedgehog cactus | Cactaceae | |
| Echinocereus pectinatus | rainbow cactus | Cactaceae | |
| Echinocereus pectinatus var. pectinatus | rainbow cactus | Cactaceae | |
| Echinocereus polyacanthus | Mojave mound cactus | Cactaceae | |
| Echinocereus rigidissimus | rainbow hedgehog cactus | Cactaceae | |
| Echinocereus triglochidiatus | kingcup cactus | Cactaceae | |
| Echinocereus triglochidiatus var. triglochidiatus | kingcup cactus | Cactaceae | |
| Echinochloa | cockspur grass | Poaceae | |
| Echinochloa colona | jungle rice | Poaceae | |
| Echinochloa crus-galli | barnyardgrass | Poaceae | |
| Echinochloa crus-pavonis | gulf cockspur grass | Poaceae | |
| Echinochloa crus-pavonis var. macera | gulf cockspur grass | Poaceae | |
| Echinochloa muricata | rough barnyardgrass | Poaceae | |
| Echinochloa muricata var. microstachya | rough barnyardgrass | Poaceae | |
| Echinochloa oplismenoides | Chihuahuan cockspur | Poaceae | |
| Echinocystis | echinocystis | Cucurbitaceae | |
| Echinocystis lobata | wild cucumber | Cucurbitaceae | |
| Echinodorus | burhead | Alismataceae | |
| Echinodorus berteroi | upright burhead | Alismataceae | |
| Echinomastus | Cactaceae | ||
| Echinomastus erectocentrus | redspine fishhook cactus | Cactaceae | |
| Echinomastus intertextus | white fishhook cactus | Cactaceae | |
| Echinomastus johnsonii | Johnson's fishhook cactus | Cactaceae | |
| Echinopepon | balsam apple | Cucurbitaceae | |
| Echinopepon wrightii | wild balsam apple | Cucurbitaceae | |
| Eclipta | eclipta | Asteraceae | |
| Eclipta prostrata | false daisy | Asteraceae | |
| Egeria | egeria | Hydrocharitaceae | |
| Egeria densa | Brazilian waterweed | Hydrocharitaceae | |
| Eichhornia | water hyacinth | Pontederiaceae | |
| Eichhornia crassipes | common water hyacinth | Pontederiaceae | |
| Elaeagnus | oleaster | Elaeagnaceae | |
| Elaeagnus angustifolia | Russian olive | Elaeagnaceae | |
| Elatine | waterwort | Elatinaceae | |
| Elatine brachysperma | shortseed waterwort | Elatinaceae | |
| Elatine californica | California waterwort | Elatinaceae | |
| Elatine chilensis | Chilean waterwort | Elatinaceae | |
| Elatine rubella | southwestern waterwort | Elatinaceae | |
| Eleocharis | spikerush | Cyperaceae | |
| Eleocharis acicularis | needle spikerush | Cyperaceae | |
| Eleocharis acicularis var. acicularis | needle spikerush | Cyperaceae | |
| Eleocharis acicularis var. porcata | Cyperaceae | ||
| Eleocharis bella | beautiful spikerush | Cyperaceae | |
| Eleocharis bolanderi | Bolander's spikerush | Cyperaceae | |
| Eleocharis cancellata | Arizona spikerush | Cyperaceae | |
| Eleocharis engelmannii | Engelmann's spikerush | Cyperaceae | |
| Eleocharis flavescens | yellow spikerush | Cyperaceae | |
| Eleocharis flavescens var. thermalis | yellow spikerush | Cyperaceae | |
| Eleocharis geniculata | Canada spikesedge | Cyperaceae | |
| Eleocharis macrostachya | pale spikerush | Cyperaceae | |
| Eleocharis montana | mountain spikerush | Cyperaceae | |
| Eleocharis montevidensis | sand spikerush | Cyperaceae | |
| Eleocharis palustris | common spikerush | Cyperaceae | |
| Eleocharis palustris var. palustris | common spikerush | Cyperaceae | |
| Eleocharis parishii | Parish's spikerush | Cyperaceae | |
| Eleocharis parvula | dwarf spikerush | Cyperaceae | |
| Eleocharis quinqueflora | fewflower spikerush | Cyperaceae | |
| Eleocharis radicans | rooted spikerush | Cyperaceae | |
| Eleocharis rostellata | beaked spikerush | Cyperaceae | |
| Eleusine | goosegrass | Poaceae | |
| Eleusine indica | Indian goosegrass | Poaceae | |
| Elionurus | balsamscale grass | Poaceae | |
| Elionurus barbiculmis | woolyspike balsamscale | Poaceae | |
| Elodea | waterweed | Hydrocharitaceae | |
| Elodea bifoliata | twoleaf waterweed | Hydrocharitaceae | |
| Elodea canadensis | Canadian waterweed | Hydrocharitaceae | |
| Elymus | wildrye | Poaceae | |
| Elymus arizonicus | Arizona wheatgrass | Poaceae | |
| Elymus canadensis | Canada wildrye | Poaceae | |
| Elymus elymoides | squirreltail | Poaceae | |
| Elymus elymoides ssp. brevifolius | squirreltail | Poaceae | |
| Elymus elymoides ssp. elymoides | squirreltail | Poaceae | |
| Elymus glaucus | blue wildrye | Poaceae | |
| Elymus glaucus ssp. glaucus | blue wildrye | Poaceae | |
| Elymus interruptus | Texas wildrye | Poaceae | |
| Elymus lanceolatus | thickspike wheatgrass | Poaceae | |
| Elymus lanceolatus ssp. lanceolatus | thickspike wheatgrass | Poaceae | |
| Elymus multisetus | big squirreltail | Poaceae | |
| Elymus pinaloensis | Poaceae | ||
| Elymus pseudorepens | Poaceae | ||
| Elymus repens | quackgrass | Poaceae | |
| Elymus saundersii | Poaceae | ||
| Elymus scribneri | spreading wheatgrass | Poaceae | |
| Elymus trachycaulus | slender wheatgrass | Poaceae | |
| Elymus trachycaulus ssp. subsecundus | slender wheatgrass | Poaceae | |
| Elymus trachycaulus ssp. trachycaulus | slender wheatgrass | Poaceae | |
| Elymus virginicus | Virginia wildrye | Poaceae | |
| Elymus virginicus var. virginicus | Virginia wildrye | Poaceae | |
| Elytraria | scalystem | Acanthaceae | |
| Elytraria imbricata | purple scalystem | Acanthaceae | |
| Emmenanthe | whisperingbells | Hydrophyllaceae | |
| Emmenanthe penduliflora | whisperingbells | Hydrophyllaceae | |
| Emmenanthe penduliflora var. penduliflora | whisperingbells | Hydrophyllaceae | |
| Encelia | brittlebush | Asteraceae | |
| Encelia farinosa | brittlebush | Asteraceae | |
| Encelia frutescens | button brittlebush | Asteraceae | |
| Encelia resinifera | sticky brittlebush | Asteraceae | |
| Encelia resinifera ssp. resinifera | button brittlebush | Asteraceae | |
| Encelia resinifera ssp. tenuifolia | Asteraceae | ||
| Encelia virginensis | Virgin River brittlebush | Asteraceae | |
| Enceliopsis | sunray | Asteraceae | |
| Enceliopsis argophylla | silverleaf sunray | Asteraceae | |
| Enceliopsis nudicaulis | nakedstem sunray | Asteraceae | |
| Enceliopsis nudicaulis var. nudicaulis | nakedstem sunray | Asteraceae | |
| Engelmannia | Engelmann's daisy | Asteraceae | |
| Engelmannia peristenia | Engelmann's daisy | Asteraceae | |
| Enneapogon | feather pappusgrass | Poaceae | |
| Enneapogon cenchroides | soft feather pappusgrass | Poaceae | |
| Enneapogon desvauxii | nineawn pappusgrass | Poaceae | |
| Enteropogon | unbrellagrass | Poaceae | |
| Enteropogon chlorideus | buryseed umbrellagrass | Poaceae | |
| Ephedra | jointfir | Ephedraceae | |
| Ephedra arenicola | Ephedraceae | ||
| Ephedra aspera | rough jointfir | Ephedraceae | |
| Ephedra californica | California jointfir | Ephedraceae | |
| Ephedra cutleri | Cutler's jointfir | Ephedraceae | |
| Ephedra fasciculata | Arizona jointfir | Ephedraceae | |
| Ephedra funerea | Death Valley jointfir | Ephedraceae | |
| Ephedra nevadensis | Nevada jointfir | Ephedraceae | |
| Ephedra torreyana | Torrey's jointfir | Ephedraceae | |
| Ephedra torreyana var. torreyana | Torrey's jointfir | Ephedraceae | |
| Ephedra trifurca | longleaf jointfir | Ephedraceae | |
| Ephedra viridis | mormon tea | Ephedraceae | |
| Epilobium | willowherb | Onagraceae | |
| Epilobium brachycarpum | tall annual willowherb | Onagraceae | |
| Epilobium canum | hummingbird trumpet | Onagraceae | |
| Epilobium canum ssp. garrettii | Garrett's firechalice | Onagraceae | |
| Epilobium canum ssp. latifolium | hummingbird trumpet | Onagraceae | |
| Epilobium ciliatum | fringed willowherb | Onagraceae | |
| Epilobium ciliatum ssp. ciliatum | fringed willowherb | Onagraceae | |
| Epilobium ciliatum ssp. glandulosum | fringed willowherb | Onagraceae | |
| Epilobium densiflorum | denseflower willowherb | Onagraceae | |
| Epilobium foliosum | leafy willowherb | Onagraceae | |
| Epilobium halleanum | glandular willowherb | Onagraceae | |
| Epilobium hornemannii | Hornemann's willowherb | Onagraceae | |
| Epilobium hornemannii ssp. hornemannii | Hornemann's willowherb | Onagraceae | |
| Epilobium lactiflorum | milkflower willowherb | Onagraceae | |
| Epilobium minutum | chaparral willowherb | Onagraceae | |
| Epilobium oregonense | Oregon willowherb | Onagraceae | |
| Epilobium pygmaeum | smooth spike-primrose | Onagraceae | |
| Epilobium saximontanum | Rocky Mountain willowherb | Onagraceae | |
| Epipactis | helleborine | Orchidaceae | |
| Epipactis gigantea | stream orchid | Orchidaceae | |
| Epithelantha | pingpong-ball cactus | Cactaceae | |
| Epithelantha micromeris | pingpong-ball cactus | Cactaceae | |
| Epixiphium | epixiphium | Scrophulariaceae | |
| Epixiphium wislizeni | balloonbush | Scrophulariaceae | |
| Equisetum | horsetail | Equisetaceae | |
| Equisetum arvense | field horsetail | Equisetaceae | |
| Equisetum ferrissii | Equisetaceae | ||
| Equisetum hyemale | scouringrush horsetail | Equisetaceae | |
| Equisetum hyemale var. affine | scouringrush horsetail | Equisetaceae | |
| Equisetum laevigatum | smooth horsetail | Equisetaceae | |
| Eragrostis | lovegrass | Poaceae | |
| Eragrostis barrelieri | Mediterranean lovegrass | Poaceae | |
| Eragrostis cilianensis | stinkgrass | Poaceae | |
| Eragrostis curvula | weeping lovegrass | Poaceae | |
| Eragrostis echinochloidea | African lovegrass | Poaceae | |
| Eragrostis intermedia | plains lovegrass | Poaceae | |
| Eragrostis lehmanniana | Lehmann lovegrass | Poaceae | |
| Eragrostis lutescens | sixweeks lovegrass | Poaceae | |
| Eragrostis mexicana | Mexican lovegrass | Poaceae | |
| Eragrostis mexicana ssp. mexicana | Mexican lovegrass | Poaceae | |
| Eragrostis mexicana ssp. virescens | Mexican lovegrass | Poaceae | |
| Eragrostis obtusiflora | alkali lovegrass | Poaceae | |
| Eragrostis pectinacea | tufted lovegrass | Poaceae | |
| Eragrostis pectinacea var. miserrima | desert lovegrass | Poaceae | |
| Eragrostis pectinacea var. pectinacea | tufted lovegrass | Poaceae | |
| Eragrostis pilosa | Indian lovegrass | Poaceae | |
| Eragrostis spectabilis | purple lovegrass | Poaceae | |
| Eragrostis superba | Wilman lovegrass | Poaceae | |
| Eremalche | mallow | Malvaceae | |
| Eremalche exilis | white mallow | Malvaceae | |
| Eremalche rotundifolia | desert fivespot | Malvaceae | |
| Eremocrinum | eremocrinum | Liliaceae | |
| Eremocrinum albomarginatum | lonely lily | Liliaceae | |
| Eremopyrum | false wheatgrass | Poaceae | |
| Eremopyrum triticeum | annual wheatgrass | Poaceae | |
| Eriastrum | woollystar | Polemoniaceae | |
| Eriastrum diffusum | miniature woollystar | Polemoniaceae | |
| Eriastrum eremicum | desert woollystar | Polemoniaceae | |
| Eriastrum eremicum ssp. eremicum | desert woollystar | Polemoniaceae | |
| Eriastrum eremicum ssp. yageri | Yager's woollystar | Polemoniaceae | |
| Ericameria | goldenbush | Asteraceae | |
| Ericameria cervina | deer goldenbush | Asteraceae | |
| Ericameria cuneata | cliff goldenbush | Asteraceae | |
| Ericameria cuneata var. spathulata | cliff goldenbush | Asteraceae | |
| Ericameria laricifolia | turpentine bush | Asteraceae | |
| Ericameria linearifolia | narrowleaf goldenbush | Asteraceae | |
| Ericameria nauseosa | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. consimilis | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. consimilis var. arenaria | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. consimilis var. juncea | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. consimilis var. leiosperma | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. consimilis var. nitida | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. consimilis var. oreophila | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. consimilis var. turbinata | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. nauseosa | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. nauseosa var. bigelovii | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. nauseosa var. glabrata | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. nauseosa var. hololeuca | rubber rabbitbrush | Asteraceae | |
| Ericameria nauseosa ssp. nauseosa var. latisquamea | rubber rabbitbrush | Asteraceae | |
| Ericameria paniculata | Mojave rabbitbrush | Asteraceae | |
| Ericameria parryi | Parry's rabbitbrush | Asteraceae | |
| Ericameria parryi var. attenuata | Parry's rabbitbrush | Asteraceae | |
| Ericameria parryi var. howardii | Parry's rabbitbrush | Asteraceae | |
| Ericameria parryi var. nevadensis | Parry's rabbitbrush | Asteraceae | |
| Ericameria teretifolia | green rabbitbrush | Asteraceae | |
| Ericameria watsonii | Watson's goldenbush | Asteraceae | |
| Erigeron | fleabane | Asteraceae | |
| Erigeron anchana | Sierra Ancha fleabane | Asteraceae | |
| Erigeron aphanactis | rayless shaggy fleabane | Asteraceae | |
| Erigeron aphanactis var. aphanactis | rayless shaggy fleabane | Asteraceae | |
| Erigeron arisolius | arid throne fleabane | Asteraceae | |
| Erigeron arizonicus | Arizona fleabane | Asteraceae | |
| Erigeron bellidiastrum | western daisy fleabane | Asteraceae | |
| Erigeron bellidiastrum var. bellidiastrum | western daisy fleabane | Asteraceae | |
| Erigeron caespitosus | tufted fleabane | Asteraceae | |
| Erigeron canus | hoary fleabane | Asteraceae | |
| Erigeron colomexicanus | running fleabane | Asteraceae | |
| Erigeron compactus | cushion daisy | Asteraceae | |
| Erigeron compositus | cutleaf daisy | Asteraceae | |
| Erigeron concinnus | Navajo fleabane | Asteraceae | |
| Erigeron concinnus var. concinnus | Navajo fleabane | Asteraceae | |
| Erigeron concinnus var. condensatus | Navajo fleabane | Asteraceae | |
| Erigeron concinnus var. subglaber | Navajo fleabane | Asteraceae | |
| Erigeron consimilis | foothill fleabane | Asteraceae | |
| Erigeron divergens | spreading fleabane | Asteraceae | |
| Erigeron eatonii | Eaton's fleabane | Asteraceae | |
| Erigeron eatonii var. eatonii | Eaton's fleabane | Asteraceae | |
| Erigeron eximius | sprucefir fleabane | Asteraceae | |
| Erigeron flagellaris | trailing fleabane | Asteraceae | |
| Erigeron formosissimus | beautiful fleabane | Asteraceae | |
| Erigeron heliographis | Heliograph Peak fleabane | Asteraceae | |
| Erigeron kuschei | Chiricahua fleabane | Asteraceae | |
| Erigeron lemmonii | Lemmon's fleabane | Asteraceae | |
| Erigeron lobatus | lobed fleabane | Asteraceae | |
| Erigeron lonchophyllus | shortray fleabane | Asteraceae | |
| Erigeron modestus | plains fleabane | Asteraceae | |
| Erigeron neomexicanus | New Mexico fleabane | Asteraceae | |
| Erigeron oreophilus | chaparral fleabane | Asteraceae | |
| Erigeron oxyphyllus | wand fleabane | Asteraceae | |
| Erigeron piscaticus | Fish Creek fleabane | Asteraceae | |
| Erigeron pringlei | Pringle's fleabane | Asteraceae | |
| Erigeron pumilus | shaggy fleabane | Asteraceae | |
| Erigeron pumilus ssp. pumilus | shaggy fleabane | Asteraceae | |
| Erigeron rhizomatus | rhizome fleabane | Asteraceae | |
| Erigeron saxatilis | rock fleabane | Asteraceae | |
| Erigeron sceptrifer | scepterbearing fleabane | Asteraceae | |
| Erigeron scopulinus | Winn Falls fleabane | Asteraceae | |
| Erigeron simplex | onestem fleabane | Asteraceae | |
| Erigeron sivinskii | Sivinsk's erigeron | Asteraceae | |
| Erigeron speciosus | aspen fleabane | Asteraceae | |
| Erigeron speciosus var. macranthus | aspen fleabane | Asteraceae | |
| Erigeron tener | slender fleabane | Asteraceae | |
| Erigeron ursinus | Bear River fleabane | Asteraceae | |
| Erigeron utahensis | Utah fleabane | Asteraceae | |
| Erigeron utahensis var. sparsifolius | Utah fleabane | Asteraceae | |
| Erigeron utahensis var. utahensis | Utah fleabane | Asteraceae | |
| Erigeron velutipes | Chihuahuan fleabane | Asteraceae | |
| Erigeron versicolor | changing fleabane | Asteraceae | |
| Erigeron vreelandii | Vreeland's erigeron | Asteraceae | |
| Eriochloa | cupgrass | Poaceae | |
| Eriochloa acuminata | tapertip cupgrass | Poaceae | |
| Eriochloa acuminata var. acuminata | tapertip cupgrass | Poaceae | |
| Eriochloa acuminata var. minor | tapertip cupgrass | Poaceae | |
| Eriochloa aristata | bearded cupgrass | Poaceae | |
| Eriochloa contracta | prairie cupgrass | Poaceae | |
| Eriochloa fatmensis | tropical cupgrass | Poaceae | |
| Eriochloa lemmonii | canyon cupgrass | Poaceae | |
| Eriodictyon | yerba santa | Hydrophyllaceae | |
| Eriodictyon angustifolium | narrowleaf yerba santa | Hydrophyllaceae | |
| Eriogonum | buckwheat | Polygonaceae | |
| Eriogonum abertianum | Abert's buckwheat | Polygonaceae | |
| Eriogonum alatum | winged buckwheat | Polygonaceae | |
| Eriogonum alatum var. alatum | winged buckwheat | Polygonaceae | |
| Eriogonum alatum var. mogollense | winged buckwheat | Polygonaceae | |
| Eriogonum arizonicum | Arizona buckwheat | Polygonaceae | |
| Eriogonum brachypodum | Parry's buckwheat | Polygonaceae | |
| Eriogonum caespitosum | matted buckwheat | Polygonaceae | |
| Eriogonum capillare | San Carlos buckwheat | Polygonaceae | |
| Eriogonum cernuum | nodding buckwheat | Polygonaceae | |
| Eriogonum cernuum var. cernuum | nodding buckwheat | Polygonaceae | |
| Eriogonum corymbosum | crispleaf buckwheat | Polygonaceae | |
| Eriogonum corymbosum var. corymbosum | crispleaf buckwheat | Polygonaceae | |
| Eriogonum corymbosum var. glutinosum | crispleaf buckwheat | Polygonaceae | |
| Eriogonum corymbosum var. orbiculatum | crispleaf buckwheat | Polygonaceae | |
| Eriogonum corymbosum var. velutinum | crispleaf buckwheat | Polygonaceae | |
| Eriogonum darrovii | Darrow's buckwheat | Polygonaceae | |
| Eriogonum davidsonii | Davidson's buckwheat | Polygonaceae | |
| Eriogonum deflexum | flatcrown buckwheat | Polygonaceae | |
| Eriogonum deflexum var. deflexum | flatcrown buckwheat | Polygonaceae | |
| Eriogonum deserticola | Colorado Desert buckwheat | Polygonaceae | |
| Eriogonum divaricatum | divergent buckwheat | Polygonaceae | |
| Eriogonum ericifolium | Yavapai County buckwheat | Polygonaceae | |
| Eriogonum ericifolium var. ericifolium | Yavapai County buckwheat | Polygonaceae | |
| Eriogonum fasciculatum | Eastern Mojave buckwheat | Polygonaceae | |
| Eriogonum fasciculatum var. foliolosum | Eastern Mojave buckwheat | Polygonaceae | |
| Eriogonum fasciculatum var. polifolium | Eastern Mojave buckwheat | Polygonaceae | |
| Eriogonum gordonii | Gordon's buckwheat | Polygonaceae | |
| Eriogonum heermannii | Heermann's buckwheat | Polygonaceae | |
| Eriogonum heermannii var. apachense | Apache buckwheat | Polygonaceae | |
| Eriogonum heermannii var. argense | Heermann's buckwheat | Polygonaceae | |
| Eriogonum heermannii var. floccosum | Clark Mountain buckwheat | Polygonaceae | |
| Eriogonum heermannii var. subracemosum | Heermann's buckwheat | Polygonaceae | |
| Eriogonum heermannii var. subspinosum | Heermann's buckwheat | Polygonaceae | |
| Eriogonum heermannii var. sulcatum | Heermann's buckwheat | Polygonaceae | |
| Eriogonum hieraciifolium | hawkweed buckwheat | Polygonaceae | |
| Eriogonum hookeri | Hooker's buckwheat | Polygonaceae | |
| Eriogonum inflatum | desert trumpet | Polygonaceae | |
| Eriogonum inflatum var. deflatum | desert trumpet | Polygonaceae | |
| Eriogonum inflatum var. inflatum | desert trumpet | Polygonaceae | |
| Eriogonum insigne | ladder buckwheat | Polygonaceae | |
| Eriogonum jamesii | James' buckwheat | Polygonaceae | |
| Eriogonum jamesii var. flavescens | James' buckwheat | Polygonaceae | |
| Eriogonum jamesii var. jamesii | James' buckwheat | Polygonaceae | |
| Eriogonum jamesii var. undulatum | James' buckwheat | Polygonaceae | |
| Eriogonum jonesii | Jones' buckwheat | Polygonaceae | |
| Eriogonum lachnogynum | woollycup buckwheat | Polygonaceae | |
| Eriogonum leptocladon | sand buckwheat | Polygonaceae | |
| Eriogonum leptocladon var. leptocladon | sand buckwheat | Polygonaceae | |
| Eriogonum leptocladon var. papiliunculi | sand buckwheat | Polygonaceae | |
| Eriogonum leptocladon var. ramosissimum | sand buckwheat | Polygonaceae | |
| Eriogonum leptophyllum | slenderleaf buckwheat | Polygonaceae | |
| Eriogonum maculatum | spotted buckwheat | Polygonaceae | |
| Eriogonum microthecum | slender buckwheat | Polygonaceae | |
| Eriogonum microthecum var. laxiflorum | slender buckwheat | Polygonaceae | |
| Eriogonum microthecum var. simpsonii | Simpson's buckwheat | Polygonaceae | |
| Eriogonum mortonianum | Fredonia buckwheat | Polygonaceae | |
| Eriogonum nidularium | birdnest buckwheat | Polygonaceae | |
| Eriogonum nummulare | money buckwheat | Polygonaceae | |
| Eriogonum ovalifolium | cushion buckwheat | Polygonaceae | |
| Eriogonum ovalifolium var. purpureum | cushion buckwheat | Polygonaceae | |
| Eriogonum palmerianum | Palmer's buckwheat | Polygonaceae | |
| Eriogonum parishii | mountainmist | Polygonaceae | |
| Eriogonum pharnaceoides | wirestem buckwheat | Polygonaceae | |
| Eriogonum pharnaceoides var. cervinum | wirestem buckwheat | Polygonaceae | |
| Eriogonum pharnaceoides var. pharnaceoides | wirestem buckwheat | Polygonaceae | |
| Eriogonum plumatella | yucca buckwheat | Polygonaceae | |
| Eriogonum polycladon | sorrel buckwheat | Polygonaceae | |
| Eriogonum pulchrum | Yavapai County buckwheat | Polygonaceae | |
| Eriogonum pusillum | yellowturbans | Polygonaceae | |
| Eriogonum racemosum | redroot buckwheat | Polygonaceae | |
| Eriogonum reniforme | kidneyleaf buckwheat | Polygonaceae | |
| Eriogonum ripleyi | Fraziers Well buckwheat | Polygonaceae | |
| Eriogonum rotundifolium | roundleaf buckwheat | Polygonaceae | |
| Eriogonum shockleyi | Shockley's buckwheat | Polygonaceae | |
| Eriogonum subreniforme | kidneyshape buckwheat | Polygonaceae | |
| Eriogonum thomasii | Thomas' buckwheat | Polygonaceae | |
| Eriogonum thompsoniae | Thompson's buckwheat | Polygonaceae | |
| Eriogonum thompsoniae var. albiflorum | Thompson's buckwheat | Polygonaceae | |
| Eriogonum thompsoniae var. atwoodii | Atwood's buckwheat | Polygonaceae | |
| Eriogonum thompsoniae var. thompsoniae | Thompson's buckwheat | Polygonaceae | |
| Eriogonum thurberi | Thurber's buckwheat | Polygonaceae | |
| Eriogonum trichopes | little deserttrumpet | Polygonaceae | |
| Eriogonum trichopes var. trichopes | little deserttrumpet | Polygonaceae | |
| Eriogonum umbellatum | sulphur-flower buckwheat | Polygonaceae | |
| Eriogonum umbellatum var. cognatum | sulphur-flower buckwheat | Polygonaceae | |
| Eriogonum umbellatum var. nevadense | sulphur-flower buckwheat | Polygonaceae | |
| Eriogonum umbellatum var. subaridum | sulphur-flower buckwheat | Polygonaceae | |
| Eriogonum viridulum | clay hill buckwheat | Polygonaceae | |
| Eriogonum wetherillii | Wetherill's buckwheat | Polygonaceae | |
| Eriogonum wrightii | bastardsage | Polygonaceae | |
| Eriogonum wrightii var. nodosum | bastardsage | Polygonaceae | |
| Eriogonum wrightii var. pringlei | Pringle's bastardsage | Polygonaceae | |
| Eriogonum wrightii var. wrightii | bastardsage | Polygonaceae | |
| Eriogonum zionis | Zion buckwheat | Polygonaceae | |
| Eriogonum zionis var. coccineum | Zion buckwheat | Polygonaceae | |
| Eriogonum zionis var. zionis | Zion buckwheat | Polygonaceae | |
| Erioneuron | woollygrass | Poaceae | |
| Erioneuron avenaceum | shortleaf woollygrass | Poaceae | |
| Erioneuron pilosum | hairy woollygrass | Poaceae | |
| Eriophyllum | woolly sunflower | Asteraceae | |
| Eriophyllum confertiflorum | golden-yarrow | Asteraceae | |
| Eriophyllum confertiflorum var. confertiflorum | golden-yarrow | Asteraceae | |
| Eriophyllum multicaule | manystem woolly sunflower | Asteraceae | |
| Eriophyllum pringlei | Pringle's woolly sunflower | Asteraceae | |
| Erodium | stork's bill | Geraniaceae | |
| Erodium cicutarium | redstem stork's bill | Geraniaceae | |
| Erodium cicutarium ssp. cicutarium | redstem stork's bill | Geraniaceae | |
| Erodium moschatum | musky stork's bill | Geraniaceae | |
| Erodium moschatum var. moschatum | musky stork's bill | Geraniaceae | |
| Erodium texanum | Texas stork's bill | Geraniaceae | |
| Errazurizia | dunebroom | Fabaceae | |
| Errazurizia rotundata | roundleaf dunebroom | Fabaceae | |
| Eruca | rocketsalad | Brassicaceae | |
| Eruca vesicaria | rocketsalad | Brassicaceae | |
| Eruca vesicaria ssp. sativa | rocketsalad | Brassicaceae | |
| Eryngium | eryngo | Apiaceae | |
| Eryngium heterophyllum | Wright's eryngo | Apiaceae | |
| Eryngium lemmonii | Chiricahua Mountain eryngo | Apiaceae | |
| Eryngium nasturtiifolium | hierba del sapo | Apiaceae | |
| Eryngium phyteumae | Huachuca Mountain eryngo | Apiaceae | |
| Eryngium sparganophyllum | Arizona eryngo | Apiaceae | |
| Erysimum | wallflower | Brassicaceae | |
| Erysimum capitatum | sanddune wallflower | Brassicaceae | |
| Erysimum capitatum var. capitatum | sanddune wallflower | Brassicaceae | |
| Erysimum capitatum var. purshii | Pursh's wallflower | Brassicaceae | |
| Erysimum cheiranthoides | wormseed wallflower | Brassicaceae | |
| Erysimum inconspicuum | shy wallflower | Brassicaceae | |
| Erysimum inconspicuum var. inconspicuum | shy wallflower | Brassicaceae | |
| Erysimum repandum | spreading wallflower | Brassicaceae | |
| Erythrina | erythrina | Fabaceae | |
| Erythrina flabelliformis | coralbean | Fabaceae | |
| Eschscholzia | California poppy | Papaveraceae | |
| Eschscholzia californica | California poppy | Papaveraceae | |
| Eschscholzia californica ssp. californica | California poppy | Papaveraceae | |
| Eschscholzia californica ssp. mexicana | California poppy | Papaveraceae | |
| Eschscholzia glyptosperma | desert poppy | Papaveraceae | |
| Eschscholzia minutiflora | pygmy poppy | Papaveraceae | |
| Eschscholzia minutiflora ssp. minutiflora | pygmy poppy | Papaveraceae | |
| Escobaria | foxtail cactus | Cactaceae | |
| Escobaria alversonii | cushion foxtail cactus | Cactaceae | |
| Escobaria missouriensis | Missouri foxtail cactus | Cactaceae | |
| Escobaria orcuttii | Orcutt's foxtail cactus | Cactaceae | |
| Escobaria orcuttii var. orcuttii | Orcutt's foxtail cactus | Cactaceae | |
| Escobaria robbinsiorum | Cochise foxtail cactus | Cactaceae | |
| Escobaria tuberculosa | whitecolumn foxtail cactus | Cactaceae | |
| Escobaria vivipara | spinystar | Cactaceae | |
| Escobaria vivipara var. arizonica | Arizona spinystar | Cactaceae | |
| Escobaria vivipara var. bisbeeana | Bisbee spinystar | Cactaceae | |
| Escobaria vivipara var. buoflama | spinystar | Cactaceae | |
| Escobaria vivipara var. deserti | desert spinystar | Cactaceae | |
| Escobaria vivipara var. kaibabensis | Kaibab spinystar | Cactaceae | |
| Escobaria vivipara var. rosea | spinystar | Cactaceae | |
| Escobaria vivipara var. vivipara | spinystar | Cactaceae | |
| Eucnide | stingbush | Loasaceae | |
| Eucnide rupestris | rock nettle | Loasaceae | |
| Eucnide urens | desert stingbush | Loasaceae | |
| Eucrypta | hideseed | Hydrophyllaceae | |
| Eucrypta chrysanthemifolia | spotted hideseed | Hydrophyllaceae | |
| Eucrypta chrysanthemifolia var. bipinnatifida | spotted hideseed | Hydrophyllaceae | |
| Eucrypta micrantha | dainty desert hideseed | Hydrophyllaceae | |
| Eupatoriadelphus | Asteraceae | ||
| Eupatoriadelphus maculatus | spotted trumpetweed | Asteraceae | |
| Eupatoriadelphus maculatus var. bruneri | spotted joe pye weed | Asteraceae | |
| Euphorbia | spurge | Euphorbiaceae | |
| Euphorbia aaron-rossii | Marble Canyon spurge | Euphorbiaceae | |
| Euphorbia bilobata | blackseed spurge | Euphorbiaceae | |
| Euphorbia brachycera | horned spurge | Euphorbiaceae | |
| Euphorbia chamaesula | mountain spurge | Euphorbiaceae | |
| Euphorbia crenulata | Chinese caps | Euphorbiaceae | |
| Euphorbia cuphosperma | hairy-fruit spurge | Euphorbiaceae | |
| Euphorbia cyathophora | fire on the mountain | Euphorbiaceae | |
| Euphorbia davidii | David's spurge | Euphorbiaceae | |
| Euphorbia dentata | toothed spurge | Euphorbiaceae | |
| Euphorbia dentata var. dentata | toothed spurge | Euphorbiaceae | |
| Euphorbia eriantha | beetle spurge | Euphorbiaceae | |
| Euphorbia esula | leafy spurge | Euphorbiaceae | |
| Euphorbia esula var. esula | leafy spurge | Euphorbiaceae | |
| Euphorbia exstipulata | squareseed spurge | Euphorbiaceae | |
| Euphorbia heterophylla | Mexican fireplant | Euphorbiaceae | |
| Euphorbia lathyris | moleplant | Euphorbiaceae | |
| Euphorbia macropus | Huachuca Mountain spurge | Euphorbiaceae | |
| Euphorbia marginata | snow on the mountain | Euphorbiaceae | |
| Euphorbia palmeri | woodland spurge | Euphorbiaceae | |
| Euphorbia palmeri var. palmeri | woodland spurge | Euphorbiaceae | |
| Euphorbia palmeri var. subpubens | woodland spurge | Euphorbiaceae | |
| Euphorbia peplus | petty spurge | Euphorbiaceae | |
| Euphorbia radians | sun spurge | Euphorbiaceae | |
| Euphorbia schizoloba | Mojave spurge | Euphorbiaceae | |
| Euphorbia spathulata | warty spurge | Euphorbiaceae | |
| Eurybia | aster | Asteraceae | |
| Eurybia glauca | gray aster | Asteraceae | |
| Eurybia pulchra | beautiful aster | Asteraceae | |
| Euryops | euryops | Asteraceae | |
| Euryops multifidus | hawk's eye | Asteraceae | |
| Eustoma | prairie gentian | Gentianaceae | |
| Eustoma exaltatum | catchfly prairie gentian | Gentianaceae | |
| Eustoma exaltatum ssp. exaltatum | catchfly prairie gentian | Gentianaceae | |
| Euthamia | goldentop | Asteraceae | |
| Euthamia occidentalis | western goldentop | Asteraceae | |
| Evax | pygmy cudweed | Asteraceae | |
| Evax verna | spring pygmycudweed | Asteraceae | |
| Evax verna var. verna | spring pygmycudweed | Asteraceae | |
| Evolvulus | dwarf morning-glory | Convolvulaceae | |
| Evolvulus alsinoides | slender dwarf morning-glory | Convolvulaceae | |
| Evolvulus alsinoides var. angustifolius | slender dwarf morning-glory | Convolvulaceae | |
| Evolvulus arizonicus | wild dwarf morning-glory | Convolvulaceae | |
| Evolvulus nuttallianus | shaggy dwarf morning-glory | Convolvulaceae | |
| Evolvulus sericeus | silver dwarf morning-glory | Convolvulaceae | |
| Evolvulus sericeus var. sericeus | silver dwarf morning-glory | Convolvulaceae | |
| Eysenhardtia | kidneywood | Fabaceae | |
| Eysenhardtia orthocarpa | Tahitian kidneywood | Fabaceae | |
| F | |||
| Fagonia | fagonbush | Zygophyllaceae | |
| Fagonia laevis | California fagonbush | Zygophyllaceae | |
| Fagonia pachyacantha | sticky fagonbush | Zygophyllaceae | |
| Fagopyrum | buckwheat | Polygonaceae | |
| Fagopyrum esculentum | buckwheat | Polygonaceae | |
| Fallugia | Apache plume | Rosaceae | |
| Fallugia paradoxa | Apache plume | Rosaceae | |
| Fendlera | fendlerbush | Hydrangeaceae | |
| Fendlera rupicola | cliff fendlerbush | Hydrangeaceae | |
| Fendlera wrightii | Wright's fendlerbush | Hydrangeaceae | |
| Fendlerella | fendlerbush | Hydrangeaceae | |
| Fendlerella utahensis | Utah fendlerbush | Hydrangeaceae | |
| Fendlerella utahensis var. cymosa | Utah fendlerbush | Hydrangeaceae | |
| Fendlerella utahensis var. utahensis | Utah fendlerbush | Hydrangeaceae | |
| Ferocactus | barrel cactus | Cactaceae | |
| Ferocactus cylindraceus | California barrel cactus | Cactaceae | |
| Ferocactus cylindraceus var. cylindraceus | California barrel cactus | Cactaceae | |
| Ferocactus cylindraceus var. lecontei | Leconte's barrel cactus | Cactaceae | |
| Ferocactus eastwoodiae | California barrel cactus | Cactaceae | |
| Ferocactus emoryi | Emory's barrel cactus | Cactaceae | |
| Ferocactus wislizeni | candy barrelcactus | Cactaceae | |
| Festuca | fescue | Poaceae | |
| Festuca arizonica | Arizona fescue | Poaceae | |
| Festuca brachyphylla | alpine fescue | Poaceae | |
| Festuca brachyphylla ssp. coloradensis | Colorado fescue | Poaceae | |
| Festuca calligera | southwest fescue | Poaceae | |
| Festuca earlei | Earle's fescue | Poaceae | |
| Festuca idahoensis | Idaho fescue | Poaceae | |
| Festuca idahoensis ssp. idahoensis | Idaho fescue | Poaceae | |
| Festuca minutiflora | smallflower fescue | Poaceae | |
| Festuca rubra | red fescue | Poaceae | |
| Festuca rubra ssp. rubra | red fescue | Poaceae | |
| Festuca saximontana | Rocky Mountain fescue | Poaceae | |
| Festuca saximontana var. saximontana | Rocky Mountain fescue | Poaceae | |
| Festuca sororia | ravine fescue | Poaceae | |
| Festuca thurberi | Thurber's fescue | Poaceae | |
| Festuca valesiaca | Volga fescue | Poaceae | |
| Fimbristylis | fimbry | Cyperaceae | |
| Fimbristylis annua | annual fimbry | Cyperaceae | |
| Fimbristylis thermalis | hot springs fimbry | Cyperaceae | |
| Fimbristylis vahlii | Vahl's fimbry | Cyperaceae | |
| Fingerhuthia | Zulu fescue | Poaceae | |
| Fingerhuthia africana | Zulu fescue | Poaceae | |
| Flaveria | yellowtops | Asteraceae | |
| Flaveria campestris | alkali yellowtops | Asteraceae | |
| Flaveria macdougalii | Mcdougall's yellowtops | Asteraceae | |
| Flaveria trinervia | clustered yellowtops | Asteraceae | |
| Fleischmannia | thoroughwort | Asteraceae | |
| Fleischmannia incarnata | pink thoroughwort | Asteraceae | |
| Fleischmannia pycnocephala | lavender thoroughwort | Asteraceae | |
| Fleischmannia sonorae | Sonoran thoroughwort | Asteraceae | |
| Flourensia | tarwort | Asteraceae | |
| Flourensia cernua | American tarwort | Asteraceae | |
| Foeniculum | fennel | Apiaceae | |
| Foeniculum vulgare | sweet fennel | Apiaceae | |
| Forestiera | swampprivet | Oleaceae | |
| Forestiera pubescens | stretchberry | Oleaceae | |
| Forestiera pubescens var. pubescens | stretchberry | Oleaceae | |
| Forestiera shrevei | desert olive | Oleaceae | |
| Fouquieria | ocotillo | Fouquieriaceae | |
| Fouquieria splendens | ocotillo | Fouquieriaceae | |
| Fragaria | strawberry | Rosaceae | |
| Fragaria vesca | woodland strawberry | Rosaceae | |
| Fragaria vesca ssp. bracteata | woodland strawberry | Rosaceae | |
| Fragaria virginiana | Virginia strawberry | Rosaceae | |
| Fragaria virginiana ssp. glauca | Virginia strawberry | Rosaceae | |
| Fragaria virginiana ssp. platypetala | Virginia strawberry | Rosaceae | |
| Frangula | buckthorn | Rhamnaceae | |
| Frangula betulifolia | beechleaf frangula | Rhamnaceae | |
| Frangula betulifolia ssp. betulifolia | beechleaf frangula | Rhamnaceae | |
| Frangula betulifolia ssp. obovata | obovate buckthorn | Rhamnaceae | |
| Frangula blumeri | Rhamnaceae | ||
| Frangula californica | California buckthorn | Rhamnaceae | |
| Frangula californica ssp. ursina | California buckthorn | Rhamnaceae | |
| Frasera | green gentian | Gentianaceae | |
| Frasera albomarginata | desert frasera | Gentianaceae | |
| Frasera paniculata | tufted frasera | Gentianaceae | |
| Frasera parryi | Coahuila frasera | Gentianaceae | |
| Frasera speciosa | elkweed | Gentianaceae | |
| Fraxinus | ash | Oleaceae | |
| Fraxinus anomala | singleleaf ash | Oleaceae | |
| Fraxinus anomala var. anomala | singleleaf ash | Oleaceae | |
| Fraxinus anomala var. lowellii | singleleaf ash | Oleaceae | |
| Fraxinus cuspidata | fragrant ash | Oleaceae | |
| Fraxinus dipetala | California ash | Oleaceae | |
| Fraxinus gooddingii | Goodding's ash | Oleaceae | |
| Fraxinus greggii | Gregg's ash | Oleaceae | |
| Fraxinus papillosa | Chihuahuan ash | Oleaceae | |
| Fraxinus velutina | velvet ash | Oleaceae | |
| Fremontodendron | flannelbush | Sterculiaceae | |
| Fremontodendron californicum | California flannelbush | Sterculiaceae | |
| Fritillaria | fritillary | Liliaceae | |
| Fritillaria atropurpurea | spotted fritillary | Liliaceae | |
| Froelichia | snakecotton | Amaranthaceae | |
| Froelichia arizonica | Arizona snakecotton | Amaranthaceae | |
| Froelichia gracilis | slender snakecotton | Amaranthaceae | |
| Froelichia interrupta | Texas snakecotton | Amaranthaceae | |
| Fuirena | umbrella-sedge | Cyperaceae | |
| Fuirena simplex | western umbrella-sedge | Cyperaceae | |
| Fuirena simplex var. simplex | western umbrella-sedge | Cyperaceae | |
| Fumaria | fumitory | Fumariaceae | |
| Fumaria occidentalis | western fumitory | Fumariaceae | |
| Fumaria parviflora | fineleaf fumitory | Fumariaceae | |
| Funastrum | twinevine | Asclepiadaceae | |
| Funastrum crispum | wavyleaf twinevine | Asclepiadaceae | |
| Funastrum cynanchoides | fringed twinevine | Asclepiadaceae | |
| Funastrum cynanchoides ssp. cynanchoides | fringed twinevine | Asclepiadaceae | |
| Funastrum cynanchoides ssp. heterophyllum | Hartweg's twinevine | Asclepiadaceae | |
| Funastrum hirtellum | hairy milkweed | Asclepiadaceae | |
| G | |||
| Gaillardia | blanketflower | Asteraceae | |
| Gaillardia aristata | common gaillardia | Asteraceae | |
| Gaillardia arizonica | Arizona blanketflower | Asteraceae | |
| Gaillardia multiceps | onion blanketflower | Asteraceae | |
| Gaillardia multiceps var. multiceps | onion blanketflower | Asteraceae | |
| Gaillardia parryi | Parry's blanketflower | Asteraceae | |
| Gaillardia pinnatifida | red dome blanketflower | Asteraceae | |
| Gaillardia pinnatifida var. linearis | red dome blanketflower | Asteraceae | |
| Gaillardia pinnatifida var. pinnatifida | red dome blanketflower | Asteraceae | |
| Gaillardia pulchella | firewheel | Asteraceae | |
| Gaillardia pulchella var. pulchella | firewheel | Asteraceae | |
| Galactia | milkpea | Fabaceae | |
| Galactia wrightii | Wright's milkpea | Fabaceae | |
| Galactia wrightii var. mollissima | Wright's milkpea | Fabaceae | |
| Galactia wrightii var. wrightii | Wright's milkpea | Fabaceae | |
| Galinsoga | gallant soldier | Asteraceae | |
| Galinsoga parviflora | gallant soldier | Asteraceae | |
| Galium | bedstraw | Rubiaceae | |
| Galium aparine | stickywilly | Rubiaceae | |
| Galium bifolium | twinleaf bedstraw | Rubiaceae | |
| Galium boreale | northern bedstraw | Rubiaceae | |
| Galium collomiae | Fossil Hill Creek bedstraw | Rubiaceae | |
| Galium coloradoense | Colorado bedstraw | Rubiaceae | |
| Galium fendleri | Fendler's bedstraw | Rubiaceae | |
| Galium mexicanum | Mexican bedstraw | Rubiaceae | |
| Galium mexicanum ssp. asperrimum | Mexican bedstraw | Rubiaceae | |
| Galium microphyllum | bracted bedstraw | Rubiaceae | |
| Galium munzii | Munz's bedstraw | Rubiaceae | |
| Galium munzii ssp. ambivalens | Munz's bedstraw | Rubiaceae | |
| Galium munzii ssp. munzii | Munz's bedstraw | Rubiaceae | |
| Galium proliferum | limestone bedstraw | Rubiaceae | |
| Galium stellatum | starry bedstraw | Rubiaceae | |
| Galium stellatum ssp. eremicum | starry bedstraw | Rubiaceae | |
| Galium trifidum | threepetal bedstraw | Rubiaceae | |
| Galium trifidum ssp. subbiflorum | threepetal bedstraw | Rubiaceae | |
| Galium triflorum | fragrant bedstraw | Rubiaceae | |
| Galium uncinulatum | bristly bedstraw | Rubiaceae | |
| Galium wrightii | Wright's bedstraw | Rubiaceae | |
| Gamochaeta | everlasting | Asteraceae | |
| Gamochaeta falcata | narrowleaf purple everlasting | Asteraceae | |
| Gamochaeta purpurea | spoonleaf purple everlasting | Asteraceae | |
| Garrya | silktassel | Garryaceae | |
| Garrya flavescens | ashy silktassel | Garryaceae | |
| Garrya wrightii | Wright's silktassel | Garryaceae | |
| Gastridium | nit grass | Poaceae | |
| Gastridium phleoides | nit grass | Poaceae | |
| Gaura | beeblossom | Onagraceae | |
| Gaura coccinea | scarlet beeblossom | Onagraceae | |
| Gaura hexandra | harlequinbush | Onagraceae | |
| Gaura hexandra ssp. gracilis | harlequinbush | Onagraceae | |
| Gaura mollis | velvetweed | Onagraceae | |
| Gayophytum | groundsmoke | Onagraceae | |
| Gayophytum decipiens | deceptive groundsmoke | Onagraceae | |
| Gayophytum diffusum | spreading groundsmoke | Onagraceae | |
| Gayophytum diffusum ssp. parviflorum | spreading groundsmoke | Onagraceae | |
| Gayophytum racemosum | blackfoot groundsmoke | Onagraceae | |
| Gayophytum ramosissimum | pinyon groundsmoke | Onagraceae | |
| Gentiana | gentian | Gentianaceae | |
| Gentiana affinis | pleated gentian | Gentianaceae | |
| Gentiana fremontii | moss gentian | Gentianaceae | |
| Gentianella | dwarf gentian | Gentianaceae | |
| Gentianella amarella | autumn dwarf gentian | Gentianaceae | |
| Gentianella amarella ssp. acuta | autumn dwarf gentian | Gentianaceae | |
| Gentianella amarella ssp. heterosepala | autumn dwarf gentian | Gentianaceae | |
| Gentianella microcalyx | Chiricahua dwarf gentian | Gentianaceae | |
| Gentianella tenella | Dane's dwarf gentian | Gentianaceae | |
| Gentianella tenella ssp. tenella | Dane's dwarf gentian | Gentianaceae | |
| Gentianella wislizeni | Chiricahua Mountain dwarf gentian | Gentianaceae | |
| Gentianella wrightii | Wright's dwarf gentian | Gentianaceae | |
| Gentianopsis | fringed gentian | Gentianaceae | |
| Gentianopsis barbellata | perennial fringed gentian | Gentianaceae | |
| Gentianopsis macrantha | grand fringed gentian | Gentianaceae | |
| Geraea | desertsunflower | Asteraceae | |
| Geraea canescens | hairy desertsunflower | Asteraceae | |
| Geranium | geranium | Geraniaceae | |
| Geranium atropurpureum | western purple cranesbill | Geraniaceae | |
| Geranium atropurpureum var. atropurpureum | western purple cranesbill | Geraniaceae | |
| Geranium caespitosum | pineywoods geranium | Geraniaceae | |
| Geranium caespitosum var. caespitosum | pineywoods geranium | Geraniaceae | |
| Geranium caespitosum var. eremophilum | purple cluster geranium | Geraniaceae | |
| Geranium caespitosum var. fremontii | Fremont's geranium | Geraniaceae | |
| Geranium caespitosum var. parryi | Parry's geranium | Geraniaceae | |
| Geranium carolinianum | Carolina geranium | Geraniaceae | |
| Geranium carolinianum var. carolinianum | Carolina geranium | Geraniaceae | |
| Geranium lentum | Mogollon geranium | Geraniaceae | |
| Geranium richardsonii | Richardson's geranium | Geraniaceae | |
| Geranium wislizeni | Huachuca Mountain geranium | Geraniaceae | |
| Geum | avens | Rosaceae | |
| Geum aleppicum | yellow avens | Rosaceae | |
| Geum macrophyllum | largeleaf avens | Rosaceae | |
| Geum macrophyllum var. perincisum | largeleaf avens | Rosaceae | |
| Geum rossii | Ross' avens | Rosaceae | |
| Geum rossii var. turbinatum | Ross' avens | Rosaceae | |
| Geum triflorum | old man's whiskers | Rosaceae | |
| Geum triflorum var. ciliatum | old man's whiskers | Rosaceae | |
| Gilia | gilia | Polemoniaceae | |
| Gilia achilleifolia | California gilia | Polemoniaceae | |
| Gilia achilleifolia ssp. multicaulis | California gilia | Polemoniaceae | |
| Gilia capitata | bluehead gilia | Polemoniaceae | |
| Gilia capitata ssp. staminea | bluehead gilia | Polemoniaceae | |
| Gilia clivorum | purplespot gilia | Polemoniaceae | |
| Gilia clokeyi | Clokey's gilia | Polemoniaceae | |
| Gilia flavocincta | lesser yellowthroat gilia | Polemoniaceae | |
| Gilia flavocincta ssp. australis | lesser yellowthroat gilia | Polemoniaceae | |
| Gilia flavocincta ssp. flavocincta | lesser yellowthroat gilia | Polemoniaceae | |
| Gilia mexicana | El Paso gilia | Polemoniaceae | |
| Gilia minor | little gilia | Polemoniaceae | |
| Gilia ophthalmoides | eyed gilia | Polemoniaceae | |
| Gilia scopulorum | rock gilia | Polemoniaceae | |
| Gilia sinuata | rosy gilia | Polemoniaceae | |
| Gilia stellata | star gilia | Polemoniaceae | |
| Gilia transmontana | transmontane gilia | Polemoniaceae | |
| Giliastrum | Polemoniaceae | ||
| Giliastrum acerosum | bluebowls | Polemoniaceae | |
| Glandularia | mock vervain | Verbenaceae | |
| Glandularia bipinnatifida | Dakota mock vervain | Verbenaceae | |
| Glandularia bipinnatifida var. bipinnatifida | Dakota mock vervain | Verbenaceae | |
| Glandularia bipinnatifida var. ciliata | Davis Mountain mock vervain | Verbenaceae | |
| Glandularia chiricahensis | Chiricahua Mountain mock vervain | Verbenaceae | |
| Glandularia elegans | mountain mock vervain | Verbenaceae | |
| Glandularia elegans var. asperata | mountain mock vervain | Verbenaceae | |
| Glandularia elegans var. elegans | mountain mock vervain | Verbenaceae | |
| Glandularia gooddingii | southwestern mock vervain | Verbenaceae | |
| Glandularia hybrida | Verbenaceae | ||
| Glandularia pulchella | South American mock vervain | Verbenaceae | |
| Glebionis | Asteraceae | ||
| Glebionis coronarium | crowndaisy | Asteraceae | |
| Gleditsia | locust | Fabaceae | |
| Gleditsia triacanthos | honeylocust | Fabaceae | |
| Glinus | sweetjuice | Molluginaceae | |
| Glinus lotoides | lotus sweetjuice | Molluginaceae | |
| Glinus radiatus | spreading sweetjuice | Molluginaceae | |
| Glossopetalon | greasebush | Crossosomataceae | |
| Glossopetalon spinescens | spiny greasebush | Crossosomataceae | |
| Glossopetalon spinescens var. aridum | spiny greasebush | Crossosomataceae | |
| Glossopetalon spinescens var. meionandrum | spiny greasebush | Crossosomataceae | |
| Glossopetalon spinescens var. microphyllum | spiny greasebush | Crossosomataceae | |
| Glossopetalon spinescens var. spinescens | spiny greasebush | Crossosomataceae | |
| Glyceria | mannagrass | Poaceae | |
| Glyceria borealis | small floating mannagrass | Poaceae | |
| Glyceria grandis | American mannagrass | Poaceae | |
| Glyceria grandis var. grandis | American mannagrass | Poaceae | |
| Glyceria striata | fowl mannagrass | Poaceae | |
| Glycyrrhiza | licorice | Fabaceae | |
| Glycyrrhiza lepidota | American licorice | Fabaceae | |
| Glyptopleura | glyptopleura | Asteraceae | |
| Glyptopleura marginata | carveseed | Asteraceae | |
| Glyptopleura setulosa | holy dandelion | Asteraceae | |
| Gnaphalium | cudweed | Asteraceae | |
| Gnaphalium exilifolium | slender cudweed | Asteraceae | |
| Gnaphalium palustre | western marsh cudweed | Asteraceae | |
| Gomphrena | globe amaranth | Amaranthaceae | |
| Gomphrena caespitosa | tufted globe amaranth | Amaranthaceae | |
| Gomphrena nitida | pearly globe amaranth | Amaranthaceae | |
| Gomphrena sonorae | Sonoran globe amaranth | Amaranthaceae | |
| Goodyera | rattlesnake plantain | Orchidaceae | |
| Goodyera oblongifolia | western rattlesnake plantain | Orchidaceae | |
| Goodyera repens | lesser rattlesnake plantain | Orchidaceae | |
| Gossypium | cotton | Malvaceae | |
| Gossypium thurberi | Thurber's cotton | Malvaceae | |
| Graptopetalum | leatherpetal | Crassulaceae | |
| Graptopetalum bartramii | Patagonia Mountain leatherpetal | Crassulaceae | |
| Graptopetalum rusbyi | San Francisco River leatherpetal | Crassulaceae | |
| Gratiola | hedgehyssop | Scrophulariaceae | |
| Gratiola neglecta | clammy hedgehyssop | Scrophulariaceae | |
| Grayia | hopsage | Chenopodiaceae | |
| Grayia spinosa | spiny hopsage | Chenopodiaceae | |
| Grindelia | gumweed | Asteraceae | |
| Grindelia arizonica | Arizona gumweed | Asteraceae | |
| Grindelia arizonica var. arizonica | Arizona gumweed | Asteraceae | |
| Grindelia laciniata | cutleaf gumweed | Asteraceae | |
| Grindelia nuda | curlytop gumweed | Asteraceae | |
| Grindelia nuda var. aphanactis | curlytop gumweed | Asteraceae | |
| Grindelia oxylepis | Mexican gumweed | Asteraceae | |
| Grindelia papposa | Spanish gold | Asteraceae | |
| Grindelia squarrosa | curlycup gumweed | Asteraceae | |
| Grindelia squarrosa var. serrulata | curlycup gumweed | Asteraceae | |
| Grindelia squarrosa var. squarrosa | curlycup gumweed | Asteraceae | |
| Grusonia | Cactaceae | ||
| Grusonia clavata | club cholla | Cactaceae | |
| Grusonia emoryi | devil cholla | Cactaceae | |
| Grusonia kunzei | devil's cholla | Cactaceae | |
| Grusonia parishii | matted cholla | Cactaceae | |
| Guardiola | guardiola | Asteraceae | |
| Guardiola platyphylla | Apache plant | Asteraceae | |
| Guilleminea | matweed | Amaranthaceae | |
| Guilleminea densa | small matweed | Amaranthaceae | |
| Guilleminea densa var. aggregata | small matweed | Amaranthaceae | |
| Guilleminea densa var. densa | small matweed | Amaranthaceae | |
| Guillenia | mustard | Brassicaceae | |
| Guillenia lasiophylla | California mustard | Brassicaceae | |
| Gutierrezia | snakeweed | Asteraceae | |
| Gutierrezia arizonica | Arizona snakeweed | Asteraceae | |
| Gutierrezia microcephala | threadleaf snakeweed | Asteraceae | |
| Gutierrezia sarothrae | broom snakeweed | Asteraceae | |
| Gutierrezia serotina | late snakeweed | Asteraceae | |
| Gutierrezia sphaerocephala | roundleaf snakeweed | Asteraceae | |
| Gutierrezia wrightii | Wright's snakeweed | Asteraceae | |
| Gymnocarpium | oakfern | Dryopteridaceae | |
| Gymnocarpium dryopteris | western oakfern | Dryopteridaceae | |
| Gymnosperma | gymnosperma | Asteraceae | |
| Gymnosperma glutinosum | gumhead | Asteraceae | |
| H | |||
| Hackelia | stickseed | Boraginaceae | |
| Hackelia besseyi | Bessey's stickseed | Boraginaceae | |
| Hackelia floribunda | manyflower stickseed | Boraginaceae | |
| Hackelia pinetorum | Livermore stickseed | Boraginaceae | |
| Hackelia pinetorum var. pinetorum | Livermore stickseed | Boraginaceae | |
| Hackelia ursina | Chihuahuan stickseed | Boraginaceae | |
| Hackelia ursina var. diaboli | Chihuahuan stickseed | Boraginaceae | |
| Hackelia ursina var. pustulata | Chihuahuan stickseed | Boraginaceae | |
| Hackelia ursina var. ursina | Chihuahuan stickseed | Boraginaceae | |
| Hackelochloa | pitscale grass | Poaceae | |
| Hackelochloa granularis | pitscale grass | Poaceae | |
| Halenia | spurred gentian | Gentianaceae | |
| Halenia recurva | Mt. Graham spurred gentian | Gentianaceae | |
| Halimolobos | fissurewort | Brassicaceae | |
| Halimolobos diffusa | spreading fissurewort | Brassicaceae | |
| Halogeton | saltlover | Chenopodiaceae | |
| Halogeton glomeratus | saltlover | Chenopodiaceae | |
| Haplophyton | haplophyton | Apocynaceae | |
| Haplophyton crooksii | cockroachplant | Apocynaceae | |
| Harpagonella | grapplinghook | Boraginaceae | |
| Harpagonella palmeri | Palmer's grapplinghook | Boraginaceae | |
| Harpagonella palmeri var. arizonica | Arizona grapplinghook | Boraginaceae | |
| Harpagonella palmeri var. palmeri | Palmer's grapplinghook | Boraginaceae | |
| Hedeoma | false pennyroyal | Lamiaceae | |
| Hedeoma costata | ribbed false pennyroyal | Lamiaceae | |
| Hedeoma costata var. pulchella | ribbed false pennyroyal | Lamiaceae | |
| Hedeoma dentata | dentate false pennyroyal | Lamiaceae | |
| Hedeoma diffusa | spreading false pennyroyal | Lamiaceae | |
| Hedeoma drummondii | Drummond's false pennyroyal | Lamiaceae | |
| Hedeoma hyssopifolia | aromatic false pennyroyal | Lamiaceae | |
| Hedeoma nana | dwarf false pennyroyal | Lamiaceae | |
| Hedeoma nana ssp. californica | California false pennyroyal | Lamiaceae | |
| Hedeoma nana ssp. macrocalyx | dwarf false pennyroyal | Lamiaceae | |
| Hedeoma nana ssp. nana | dwarf false pennyroyal | Lamiaceae | |
| Hedeoma oblongifolia | oblongleaf false pennyroyal | Lamiaceae | |
| Hedera | ivy | Araliaceae | |
| Hedera colchica | colchis ivy | Araliaceae | |
| Hedera helix | English ivy | Araliaceae | |
| Hedosyne | Asteraceae | ||
| Hedosyne ambrosiifolia | ragged marsh-elder | Asteraceae | |
| Hedyotis | starviolet | Rubiaceae | |
| Hedyotis greenei | Greene's starviolet | Rubiaceae | |
| Hedyotis vegrandis | New Mexico starviolet | Rubiaceae | |
| Hedypnois | hedypnois | Asteraceae | |
| Hedypnois cretica | Cretanweed | Asteraceae | |
| Hedysarum | sweetvetch | Fabaceae | |
| Hedysarum boreale | Utah sweetvetch | Fabaceae | |
| Hedysarum boreale ssp. boreale | Utah sweetvetch | Fabaceae | |
| Hedysarum boreale ssp. boreale var. boreale | Utah sweetvetch | Fabaceae | |
| Helenium | sneezeweed | Asteraceae | |
| Helenium arizonicum | Arizona sneezeweed | Asteraceae | |
| Helenium autumnale | common sneezeweed | Asteraceae | |
| Helenium autumnale var. autumnale | common sneezeweed | Asteraceae | |
| Helenium autumnale var. montanum | mountain sneezeweed | Asteraceae | |
| Helenium bigelovii | Bigelow's sneezeweed | Asteraceae | |
| Helenium thurberi | Thurber's sneezeweed | Asteraceae | |
| Helianthella | helianthella | Asteraceae | |
| Helianthella microcephala | purpledisk helianthella | Asteraceae | |
| Helianthella parryi | Parry's dwarf-sunflower | Asteraceae | |
| Helianthella quinquenervis | fivenerve helianthella | Asteraceae | |
| Helianthus | sunflower | Asteraceae | |
| Helianthus annuus | common sunflower | Asteraceae | |
| Helianthus anomalus | western sunflower | Asteraceae | |
| Helianthus arizonensis | Arizona sunflower | Asteraceae | |
| Helianthus ciliaris | Texas blueweed | Asteraceae | |
| Helianthus niveus | showy sunflower | Asteraceae | |
| Helianthus niveus ssp. canescens | showy sunflower | Asteraceae | |
| Helianthus niveus ssp. tephrodes | Algodones sunflower | Asteraceae | |
| Helianthus nuttallii | Nuttall's sunflower | Asteraceae | |
| Helianthus nuttallii ssp. nuttallii | Nuttall's sunflower | Asteraceae | |
| Helianthus pauciflorus | stiff sunflower | Asteraceae | |
| Helianthus pauciflorus ssp. subrhomboideus | stiff sunflower | Asteraceae | |
| Helianthus petiolaris | prairie sunflower | Asteraceae | |
| Helianthus petiolaris ssp. fallax | prairie sunflower | Asteraceae | |
| Helianthus petiolaris ssp. petiolaris | prairie sunflower | Asteraceae | |
| Heliomeris | false goldeneye | Asteraceae | |
| Heliomeris hispida | rough false goldeneye | Asteraceae | |
| Heliomeris longifolia | longleaf false goldeneye | Asteraceae | |
| Heliomeris longifolia var. annua | longleaf false goldeneye | Asteraceae | |
| Heliomeris longifolia var. longifolia | longleaf false goldeneye | Asteraceae | |
| Heliomeris multiflora | showy goldeneye | Asteraceae | |
| Heliomeris multiflora var. brevifolia | showy goldeneye | Asteraceae | |
| Heliomeris multiflora var. macrocephala | Asteraceae | ||
| Heliomeris multiflora var. multiflora | showy goldeneye | Asteraceae | |
| Heliomeris multiflora var. nevadensis | Nevada goldeneye | Asteraceae | |
| Heliopsis | heliopsis | Asteraceae | |
| Heliopsis parvifolia | mountain oxeye | Asteraceae | |
| Heliotropium | heliotrope | Boraginaceae | |
| Heliotropium convolvulaceum | phlox heliotrope | Boraginaceae | |
| Heliotropium convolvulaceum var. californicum | phlox heliotrope | Boraginaceae | |
| Heliotropium convolvulaceum var. convolvulaceum | phlox heliotrope | Boraginaceae | |
| Heliotropium curassavicum | salt heliotrope | Boraginaceae | |
| Heliotropium curassavicum var. curassavicum | salt heliotrope | Boraginaceae | |
| Heliotropium curassavicum var. oculatum | seaside heliotrope | Boraginaceae | |
| Heliotropium fruticosum | Key West heliotrope | Boraginaceae | |
| Heliotropium pringlei | Pringle's heliotrope | Boraginaceae | |
| Heliotropium procumbens | fourspike heliotrope | Boraginaceae | |
| Heliotropium procumbens var. procumbens | fourspike heliotrope | Boraginaceae | |
| Hemizonia | tarweed | Asteraceae | |
| Hemizonia kelloggii | Kellogg's tarweed | Asteraceae | |
| Henrya | henrya | Acanthaceae | |
| Henrya insularis | island renegade | Acanthaceae | |
| Heracleum | cowparsnip | Apiaceae | |
| Heracleum maximum | common cowparsnip | Apiaceae | |
| Herissantia | herissantia | Malvaceae | |
| Herissantia crispa | bladdermallow | Malvaceae | |
| Hermannia | hermannia | Sterculiaceae | |
| Hermannia pauciflora | Santa Catalina burstwort | Sterculiaceae | |
| Herniaria | rupturewort | Caryophyllaceae | |
| Herniaria hirsuta | hairy rupturewort | Caryophyllaceae | |
| Herniaria hirsuta ssp. cinerea | hairy rupturewort | Caryophyllaceae | |
| Hesperocallis | desert lily | Liliaceae | |
| Hesperocallis undulata | desert lily | Liliaceae | |
| Hesperochiron | hesperochiron | Hydrophyllaceae | |
| Hesperochiron pumilus | dwarf hesperochiron | Hydrophyllaceae | |
| Hesperodoria | glowweed | Asteraceae | |
| Hesperodoria salicina | willow glowweed | Asteraceae | |
| Hesperodoria scopulorum | Grand Canyon glowweed | Asteraceae | |
| Hesperostipa | needle and thread | Poaceae | |
| Hesperostipa comata | needle and thread | Poaceae | |
| Hesperostipa comata ssp. comata | needle and thread | Poaceae | |
| Hesperostipa comata ssp. intermedia | intermediate needle and thread | Poaceae | |
| Hesperostipa neomexicana | New Mexico feathergrass | Poaceae | |
| Hesperoyucca | Agavaceae | ||
| Hesperoyucca newberryi | Newberry's yucca | Agavaceae | |
| Hesperoyucca whipplei | chaparral yucca | Agavaceae | |
| Heteranthera | mudplantain | Pontederiaceae | |
| Heteranthera dubia | grassleaf mudplantain | Pontederiaceae | |
| Heteranthera limosa | blue mudplantain | Pontederiaceae | |
| Heteranthera peduncularis | egret mudplantain | Pontederiaceae | |
| Heteranthera rotundifolia | roundleaf mudplantain | Pontederiaceae | |
| Heteropogon | tanglehead | Poaceae | |
| Heteropogon contortus | tanglehead | Poaceae | |
| Heteropogon melanocarpus | sweet tanglehead | Poaceae | |
| Heterosperma | heterosperma | Asteraceae | |
| Heterosperma pinnatum | wingpetal | Asteraceae | |
| Heterotheca | false goldenaster | Asteraceae | |
| Heterotheca fulcrata | rockyscree false goldenaster | Asteraceae | |
| Heterotheca fulcrata var. amplifolia | rockyscree false goldenaster | Asteraceae | |
| Heterotheca fulcrata var. arizonica | Arizona false goldenaster | Asteraceae | |
| Heterotheca fulcrata var. fulcrata | rockyscree false goldenaster | Asteraceae | |
| Heterotheca fulcrata var. senilis | rockyscree false goldenaster | Asteraceae | |
| Heterotheca grandiflora | telegraphweed | Asteraceae | |
| Heterotheca marginata | Sonora false goldenaster | Asteraceae | |
| Heterotheca rutteri | Rutter's false goldenaster | Asteraceae | |
| Heterotheca subaxillaris | camphorweed | Asteraceae | |
| Heterotheca villosa | hairy false goldenaster | Asteraceae | |
| Heterotheca villosa var. minor | hairy false goldenaster | Asteraceae | |
| Heterotheca villosa var. nana | hairy false goldenaster | Asteraceae | |
| Heterotheca villosa var. pedunculata | hairy false goldenaster | Asteraceae | |
| Heterotheca villosa var. scabra | hairy false goldenaster | Asteraceae | |
| Heterotheca viscida | cliff false goldenaster | Asteraceae | |
| Heterotheca zionensis | Zion false goldenaster | Asteraceae | |
| Heuchera | alumroot | Saxifragaceae | |
| Heuchera eastwoodiae | Senator Mine alumroot | Saxifragaceae | |
| Heuchera glomerulata | Chiricahua Mountain alumroot | Saxifragaceae | |
| Heuchera novomexicana | New Mexico alumroot | Saxifragaceae | |
| Heuchera parvifolia | littleleaf alumroot | Saxifragaceae | |
| Heuchera parvifolia var. arizonica | Arizona alumroot | Saxifragaceae | |
| Heuchera parvifolia var. flavescens | littleleaf alumroot | Saxifragaceae | |
| Heuchera rubescens | pink alumroot | Saxifragaceae | |
| Heuchera rubescens var. rubescens | pink alumroot | Saxifragaceae | |
| Heuchera rubescens var. versicolor | pink alumroot | Saxifragaceae | |
| Heuchera sanguinea | coralbells | Saxifragaceae | |
| Heuchera sanguinea var. pulchra | coralbells | Saxifragaceae | |
| Heuchera sanguinea var. sanguinea | coralbells | Saxifragaceae | |
| Hexalectris | crested coralroot | Orchidaceae | |
| Hexalectris revoluta | Chisos Mountain crested coralroot | Orchidaceae | |
| Hexalectris spicata | spiked crested coralroot | Orchidaceae | |
| Hexalectris spicata var. arizonica | spiked crested coralroot | Orchidaceae | |
| Hexalectris spicata var. spicata | spiked crested coralroot | Orchidaceae | |
| Hexalectris warnockii | Texas crested coralroot | Orchidaceae | |
| Hibiscus | rosemallow | Malvaceae | |
| Hibiscus biseptus | Arizona rosemallow | Malvaceae | |
| Hibiscus coulteri | desert rosemallow | Malvaceae | |
| Hibiscus denudatus | paleface | Malvaceae | |
| Hibiscus trionum | flower of an hour | Malvaceae | |
| Hieracium | hawkweed | Asteraceae | |
| Hieracium carneum | Huachuca hawkweed | Asteraceae | |
| Hieracium fendleri | yellow hawkweed | Asteraceae | |
| Hieracium fendleri var. discolor | yellow hawkweed | Asteraceae | |
| Hieracium fendleri var. fendleri | yellow hawkweed | Asteraceae | |
| Hieracium fendleri var. mogollense | Mogollon hawkweed | Asteraceae | |
| Hieracium lemmonii | Lemmon's hawkweed | Asteraceae | |
| Hieracium pringlei | Pringle's hawkweed | Asteraceae | |
| Hieracium rusbyi | Rusby's hawkweed | Asteraceae | |
| Hierochloe | sweetgrass | Poaceae | |
| Hierochloe hirta | northern sweetgrass | Poaceae | |
| Hierochloe hirta ssp. arctica | northern sweetgrass | Poaceae | |
| Hilaria | curly-mesquite | Poaceae | |
| Hilaria belangeri | curly-mesquite | Poaceae | |
| Hilaria belangeri var. belangeri | curly-mesquite | Poaceae | |
| Hilaria belangeri var. longifolia | longleaf curly-mesquite | Poaceae | |
| Hippuris | mare's-tail | Hippuridaceae | |
| Hippuris vulgaris | common mare's-tail | Hippuridaceae | |
| Hoffmannseggia | rushpea | Fabaceae | |
| Hoffmannseggia drepanocarpa | sicklepod holdback | Fabaceae | |
| Hoffmannseggia glauca | Indian rushpea | Fabaceae | |
| Hoffmannseggia microphylla | wand holdback | Fabaceae | |
| Holcus | velvetgrass | Poaceae | |
| Holcus lanatus | common velvetgrass | Poaceae | |
| Holodiscus | oceanspray | Rosaceae | |
| Holodiscus discolor | oceanspray | Rosaceae | |
| Holodiscus dumosus | rockspirea | Rosaceae | |
| Hordeum | barley | Poaceae | |
| Hordeum arizonicum | Arizona barley | Poaceae | |
| Hordeum brachyantherum | meadow barley | Poaceae | |
| Hordeum brachyantherum ssp. brachyantherum | meadow barley | Poaceae | |
| Hordeum jubatum | foxtail barley | Poaceae | |
| Hordeum jubatum ssp. jubatum | foxtail barley | Poaceae | |
| Hordeum marinum | seaside barley | Poaceae | |
| Hordeum marinum ssp. gussonianum | Mediterranean barley | Poaceae | |
| Hordeum murinum | mouse barley | Poaceae | |
| Hordeum murinum ssp. glaucum | smooth barley | Poaceae | |
| Hordeum murinum ssp. leporinum | hare barley | Poaceae | |
| Hordeum murinum ssp. murinum | wall barley | Poaceae | |
| Hordeum pusillum | little barley | Poaceae | |
| Hordeum vulgare | common barley | Poaceae | |
| Hornungia | Brassicaceae | ||
| Hornungia procumbens | prostrate hutchinsia | Brassicaceae | |
| Horsfordia | velvetmallow | Malvaceae | |
| Horsfordia alata | pink velvetmallow | Malvaceae | |
| Horsfordia newberryi | Newberry's velvetmallow | Malvaceae | |
| Houstonia | bluet | Rubiaceae | |
| Houstonia pusilla | tiny bluet | Rubiaceae | |
| Houstonia rubra | red bluet | Rubiaceae | |
| Houstonia wrightii | pygmy bluet | Rubiaceae | |
| Hulsea | alpinegold | Asteraceae | |
| Hulsea heterochroma | redray alpinegold | Asteraceae | |
| Humulus | hop | Cannabaceae | |
| Humulus lupulus | common hop | Cannabaceae | |
| Humulus lupulus var. neomexicanus | common hop | Cannabaceae | |
| Hybanthus | greenviolet | Violaceae | |
| Hybanthus attenuatus | western greenviolet | Violaceae | |
| Hybanthus verticillatus | babyslippers | Violaceae | |
| Hydrilla | hydrilla | Hydrocharitaceae | |
| Hydrilla verticillata | waterthyme | Hydrocharitaceae | |
| Hydrocotyle | hydrocotyle | Apiaceae | |
| Hydrocotyle prolifera | whorled marshpennywort | Apiaceae | |
| Hydrocotyle ranunculoides | floating marshpennywort | Apiaceae | |
| Hydrocotyle verticillata | whorled marshpennywort | Apiaceae | |
| Hydrocotyle verticillata var. verticillata | whorled marshpennywort | Apiaceae | |
| Hydrophyllum | waterleaf | Hydrophyllaceae | |
| Hydrophyllum occidentale | western waterleaf | Hydrophyllaceae | |
| Hymenoclea | burrobrush | Asteraceae | |
| Hymenoclea monogyra | singlewhorl burrobrush | Asteraceae | |
| Hymenoclea salsola | burrobrush | Asteraceae | |
| Hymenoclea salsola var. fasciculata | burrobrush | Asteraceae | |
| Hymenoclea salsola var. pentalepis | burrobrush | Asteraceae | |
| Hymenoclea salsola var. salsola | burrobrush | Asteraceae | |
| Hymenopappus | hymenopappus | Asteraceae | |
| Hymenopappus filifolius | fineleaf hymenopappus | Asteraceae | |
| Hymenopappus filifolius var. cinereus | fineleaf hymenopappus | Asteraceae | |
| Hymenopappus filifolius var. lugens | fineleaf hymenopappus | Asteraceae | |
| Hymenopappus filifolius var. megacephalus | fineleaf hymenopappus | Asteraceae | |
| Hymenopappus filifolius var. nanus | fineleaf hymenopappus | Asteraceae | |
| Hymenopappus filifolius var. pauciflorus | fineleaf hymenopappus | Asteraceae | |
| Hymenopappus filifolius var. tomentosus | finehair hymenopappus | Asteraceae | |
| Hymenopappus flavescens | collegeflower | Asteraceae | |
| Hymenopappus flavescens var. canotomentosus | collegeflower | Asteraceae | |
| Hymenopappus mexicanus | Mexican woollywhite | Asteraceae | |
| Hymenopappus radiatus | ray hymenopappus | Asteraceae | |
| Hymenothrix | thimblehead | Asteraceae | |
| Hymenothrix loomisii | Loomis' thimblehead | Asteraceae | |
| Hymenothrix wislizeni | Trans-Pecos thimblehead | Asteraceae | |
| Hymenothrix wrightii | Wright's thimblehead | Asteraceae | |
| Hymenoxys | rubberweed | Asteraceae | |
| Hymenoxys ambigens | Pinaleno Mountain rubberweed | Asteraceae | |
| Hymenoxys ambigens var. ambigens | Pinaleno Mountain rubberweed | Asteraceae | |
| Hymenoxys ambigens var. floribunda | Apache Passe rubberweed | Asteraceae | |
| Hymenoxys bigelovii | Bigelow's rubberweed | Asteraceae | |
| Hymenoxys cooperi | Cooper's rubberweed | Asteraceae | |
| Hymenoxys cooperi var. canescens | Cooper's rubberweed | Asteraceae | |
| Hymenoxys cooperi var. cooperi | Cooper's rubberweed | Asteraceae | |
| Hymenoxys helenioides | Intermountain rubberweed | Asteraceae | |
| Hymenoxys hoopesii | owl's-claws | Asteraceae | |
| Hymenoxys jamesii | Jame's rubberweed | Asteraceae | |
| Hymenoxys lemmonii | Lemmon's rubberweed | Asteraceae | |
| Hymenoxys odorata | bitter rubberweed | Asteraceae | |
| Hymenoxys quinquesquamata | rincon rubberweed | Asteraceae | |
| Hymenoxys richardsonii | pingue rubberweed | Asteraceae | |
| Hymenoxys richardsonii var. floribunda | Colorado rubberweed | Asteraceae | |
| Hymenoxys rusbyi | Rusby's rubberweed | Asteraceae | |
| Hymenoxys subintegra | Arizona rubberweed | Asteraceae | |
| Hypericum | St. Johnswort | Clusiaceae | |
| Hypericum anagalloides | tinker's penny | Clusiaceae | |
| Hypericum scouleri | Scouler's St. Johnswort | Clusiaceae | |
| Hypericum scouleri ssp. scouleri | Scouler's St. Johnswort | Clusiaceae | |
| Hypoxis | star-grass | Liliaceae | |
| Hypoxis mexicana | Mexican yellow star-grass | Liliaceae | |
| Hyptis | bushmint | Lamiaceae | |
| Hyptis emoryi | desert lavender | Lamiaceae | |
| I | |||
| Ibervillea | globeberry | Cucurbitaceae | |
| Ibervillea tenuisecta | slimlobe globeberry | Cucurbitaceae | |
| Iliamna | wild hollyhock | Malvaceae | |
| Iliamna grandiflora | largeflower wild hollyhock | Malvaceae | |
| Imperata | satintail | Poaceae | |
| Imperata brevifolia | California satintail | Poaceae | |
| Indigofera | indigo | Fabaceae | |
| Indigofera sphaerocarpa | Sonoran indigo | Fabaceae | |
| Ipomoea | morning-glory | Convolvulaceae | |
| Ipomoea barbatisepala | canyon morning-glory | Convolvulaceae | |
| Ipomoea capillacea | purple morning-glory | Convolvulaceae | |
| Ipomoea cardiophylla | heartleaf morning-glory | Convolvulaceae | |
| Ipomoea costellata | crestrib morning-glory | Convolvulaceae | |
| Ipomoea cristulata | Trans-Pecos morning-glory | Convolvulaceae | |
| Ipomoea hederacea | ivyleaf morning-glory | Convolvulaceae | |
| Ipomoea leucantha | Convolvulaceae | ||
| Ipomoea longifolia | pinkthroat morning-glory | Convolvulaceae | |
| Ipomoea plummerae | Huachuca Mountain morning-glory | Convolvulaceae | |
| Ipomoea pubescens | silky morning-glory | Convolvulaceae | |
| Ipomoea purpurea | tall morning-glory | Convolvulaceae | |
| Ipomoea tenuiloba | spiderleaf | Convolvulaceae | |
| Ipomoea tenuiloba var. lemmonii | spiderleaf | Convolvulaceae | |
| Ipomoea ternifolia | tripleleaf morning-glory | Convolvulaceae | |
| Ipomoea ternifolia var. leptotoma | tripleleaf morning-glory | Convolvulaceae | |
| Ipomoea thurberi | Thurber's morning-glory | Convolvulaceae | |
| Ipomoea tricolor | grannyvine | Convolvulaceae | |
| Ipomopsis | ipomopsis | Polemoniaceae | |
| Ipomopsis aggregata | scarlet gilia | Polemoniaceae | |
| Ipomopsis aggregata ssp. formosissima | scarlet gilia | Polemoniaceae | |
| Ipomopsis arizonica | Arizona ipomopsis | Polemoniaceae | |
| Ipomopsis congesta | ballhead ipomopsis | Polemoniaceae | |
| Ipomopsis congesta ssp. frutescens | ballhead ipomopsis | Polemoniaceae | |
| Ipomopsis gunnisonii | sanddune ipomopsis | Polemoniaceae | |
| Ipomopsis laxiflora | iron ipomopsis | Polemoniaceae | |
| Ipomopsis longiflora | flaxflowered ipomopsis | Polemoniaceae | |
| Ipomopsis longiflora ssp. australis | whiteflower ipomopsis | Polemoniaceae | |
| Ipomopsis longiflora ssp. longiflora | flaxflowered ipomopsis | Polemoniaceae | |
| Ipomopsis macombii | Macomb's ipomopsis | Polemoniaceae | |
| Ipomopsis macrosiphon | longtube ipomopsis | Polemoniaceae | |
| Ipomopsis multiflora | manyflowered ipomopsis | Polemoniaceae | |
| Ipomopsis polycladon | manybranched ipomopsis | Polemoniaceae | |
| Ipomopsis pumila | dwarf ipomopsis | Polemoniaceae | |
| Ipomopsis tenuifolia | slenderleaf skyrocket | Polemoniaceae | |
| Ipomopsis tenuituba | slendertube skyrocket | Polemoniaceae | |
| Ipomopsis tenuituba ssp. latiloba | slendertube skyrocket | Polemoniaceae | |
| Ipomopsis thurberi | El Paso skyrocket | Polemoniaceae | |
| Iresine | bloodleaf | Amaranthaceae | |
| Iresine heterophylla | Standley's bloodleaf | Amaranthaceae | |
| Iris | iris | Iridaceae | |
| Iris missouriensis | Rocky Mountain iris | Iridaceae | |
| Isocoma | goldenbush | Asteraceae | |
| Isocoma acradenia | alkali goldenbush | Asteraceae | |
| Isocoma acradenia var. acradenia | alkali goldenbush | Asteraceae | |
| Isocoma acradenia var. eremophila | alkali goldenbush | Asteraceae | |
| Isocoma azteca | Aztec goldenbush | Asteraceae | |
| Isocoma pluriflora | southern goldenbush | Asteraceae | |
| Isocoma rusbyi | Rusby's goldenbush | Asteraceae | |
| Isocoma tenuisecta | burroweed | Asteraceae | |
| Isoetes | quillwort | Isoetaceae | |
| Isoetes bolanderi | Bolander's quillwort | Isoetaceae | |
| Iva | marsh elder | Asteraceae | |
| Iva axillaris | povertyweed | Asteraceae | |
| Ivesia | mousetail | Rosaceae | |
| Ivesia arizonica | rock whitefeather | Rosaceae | |
| Ivesia arizonica var. arizonica | Arizona whitefeather | Rosaceae | |
| Ivesia arizonica var. saxosa | rock whitefeather | Rosaceae | |
| Ivesia multifoliolata | manyleaf mousetail | Rosaceae | |
| Ivesia sabulosa | Intermountain mousetail | Rosaceae | |
| J | |||
| Jacquemontia | clustervine | Convolvulaceae | |
| Jacquemontia agrestis | midnightblue clustervine | Convolvulaceae | |
| Jacquemontia pringlei | Pringle's clustervine | Convolvulaceae | |
| Jaltomata | false holly | Solanaceae | |
| Jaltomata procumbens | creeping false holly | Solanaceae | |
| Jamesia | cliffbush | Hydrangeaceae | |
| Jamesia americana | fivepetal cliffbush | Hydrangeaceae | |
| Jamesia americana var. americana | fivepetal cliffbush | Hydrangeaceae | |
| Janusia | janusia | Malpighiaceae | |
| Janusia gracilis | slender janusia | Malpighiaceae | |
| Jatropha | nettlespurge | Euphorbiaceae | |
| Jatropha cardiophylla | sangre de cristo | Euphorbiaceae | |
| Jatropha cinerea | Arizona nettlespurge | Euphorbiaceae | |
| Jatropha cuneata | physicnut | Euphorbiaceae | |
| Jatropha macrorhiza | ragged nettlespurge | Euphorbiaceae | |
| Jatropha macrorhiza var. septemfida | ragged nettlespurge | Euphorbiaceae | |
| Juglans | walnut | Juglandaceae | |
| Juglans major | Arizona walnut | Juglandaceae | |
| Juncus | rush | Juncaceae | |
| Juncus acuminatus | tapertip rush | Juncaceae | |
| Juncus acutus | spiny rush | Juncaceae | |
| Juncus acutus ssp. leopoldii | Leopold's rush | Juncaceae | |
| Juncus ambiguus | seasice rush | Juncaceae | |
| Juncus arcticus | arctic rush | Juncaceae | |
| Juncus arcticus ssp. littoralis | mountain rush | Juncaceae | |
| Juncus articulatus | jointleaf rush | Juncaceae | |
| Juncus brevicaudatus | narrowpanicle rush | Juncaceae | |
| Juncus bufonius | toad rush | Juncaceae | |
| Juncus bufonius var. bufonius | toad rush | Juncaceae | |
| Juncus bufonius var. occidentalis | toad rush | Juncaceae | |
| Juncus confusus | Colorado rush | Juncaceae | |
| Juncus cooperi | Cooper's rush | Juncaceae | |
| Juncus drummondii | Drummond's rush | Juncaceae | |
| Juncus drummondii var. drummondii | Drummond's rush | Juncaceae | |
| Juncus dudleyi | Dudley's rush | Juncaceae | |
| Juncus effusus | common rush | Juncaceae | |
| Juncus effusus var. brunneus | lamp rush | Juncaceae | |
| Juncus effusus var. exiguus | lamp rush | Juncaceae | |
| Juncus effusus var. pacificus | Pacific rush | Juncaceae | |
| Juncus ensifolius | swordleaf rush | Juncaceae | |
| Juncus interior | inland rush | Juncaceae | |
| Juncus interior var. arizonicus | Arizona rush | Juncaceae | |
| Juncus interior var. interior | inland rush | Juncaceae | |
| Juncus interior var. neomexicanus | New Mexico rush | Juncaceae | |
| Juncus longistylis | longstyle rush | Juncaceae | |
| Juncus longistylis var. longistylis | longstyle rush | Juncaceae | |
| Juncus longistylis var. scabratus | longstyle rush | Juncaceae | |
| Juncus macrophyllus | longleaf rush | Juncaceae | |
| Juncus marginatus | grassleaf rush | Juncaceae | |
| Juncus mertensianus | Mertens' rush | Juncaceae | |
| Juncus mexicanus | Mexican rush | Juncaceae | |
| Juncus nevadensis | Sierra rush | Juncaceae | |
| Juncus nevadensis var. badius | Sierra rush | Juncaceae | |
| Juncus nodosus | knotted rush | Juncaceae | |
| Juncus nodosus var. nodosus | knotted rush | Juncaceae | |
| Juncus occidentalis | western rush | Juncaceae | |
| Juncus saximontanus | Rocky Mountain rush | Juncaceae | |
| Juncus tenuis | poverty rush | Juncaceae | |
| Juncus torreyi | Torrey's rush | Juncaceae | |
| Juncus tracyi | Tracy's rush | Juncaceae | |
| Juncus xiphioides | irisleaf rush | Juncaceae | |
| Juniperus | juniper | Cupressaceae | |
| Juniperus californica | California juniper | Cupressaceae | |
| Juniperus coahuilensis | redberry juniper | Cupressaceae | |
| Juniperus coahuilensis var. arizonica | redberry juniper | Cupressaceae | |
| Juniperus coahuilensis var. coahuilensis | redberry juniper | Cupressaceae | |
| Juniperus communis | common juniper | Cupressaceae | |
| Juniperus communis var. depressa | common juniper | Cupressaceae | |
| Juniperus deppeana | alligator juniper | Cupressaceae | |
| Juniperus monosperma | oneseed juniper | Cupressaceae | |
| Juniperus osteosperma | Utah juniper | Cupressaceae | |
| Juniperus scopulorum | Rocky Mountain juniper | Cupressaceae | |
| Justicia | water-willow | Acanthaceae | |
| Justicia californica | beloperone | Acanthaceae | |
| Justicia candicans | Arizona water-willow | Acanthaceae | |
| Justicia longii | longflower tube tongue | Acanthaceae | |
| Justicia sonorae | Sonoran water-willow | Acanthaceae | |
| K | |||
| Kallstroemia | caltrop | Zygophyllaceae | |
| Kallstroemia californica | California caltrop | Zygophyllaceae | |
| Kallstroemia grandiflora | Arizona poppy | Zygophyllaceae | |
| Kallstroemia hirsutissima | hairy caltrop | Zygophyllaceae | |
| Kallstroemia parviflora | warty caltrop | Zygophyllaceae | |
| Keckiella | keckiella | Scrophulariaceae | |
| Keckiella antirrhinoides | snapdragon penstemon | Scrophulariaceae | |
| Keckiella antirrhinoides ssp. microphylla | snapdragon penstemon | Scrophulariaceae | |
| Kelloggia | kelloggia | Rubiaceae | |
| Kelloggia galioides | milk kelloggia | Rubiaceae | |
| Koanophyllon | thoroughwort | Asteraceae | |
| Koanophyllon solidaginifolium | shrubby thoroughwort | Asteraceae | |
| Koeberlinia | allthorn | Capparaceae | |
| Koeberlinia spinosa | crown of thorns | Capparaceae | |
| Koeberlinia spinosa var. spinosa | crown of thorns | Capparaceae | |
| Koeberlinia spinosa var. tenuispina | crown of thorns | Capparaceae | |
| Koeleria | Junegrass | Poaceae | |
| Koeleria macrantha | prairie Junegrass | Poaceae | |
| Krameria | ratany | Krameriaceae | |
| Krameria erecta | littleleaf ratany | Krameriaceae | |
| Krameria grayi | white ratany | Krameriaceae | |
| Krameria lanceolata | trailing krameria | Krameriaceae | |
| Krascheninnikovia | winterfat | Chenopodiaceae | |
| Krascheninnikovia lanata | winterfat | Chenopodiaceae | |
| Krigia | dwarfdandelion | Asteraceae | |
| Krigia biflora | twoflower dwarfdandelion | Asteraceae | |
| Krigia biflora var. biflora | twoflower dwarfdandelion | Asteraceae | |
| Krigia biflora var. viridis | twoflower dwarfdandelion | Asteraceae | |
| L | |||
| Lactuca | lettuce | Asteraceae | |
| Lactuca graminifolia | grassleaf lettuce | Asteraceae | |
| Lactuca graminifolia var. arizonica | grassleaf lettuce | Asteraceae | |
| Lactuca ludoviciana | biannual lettuce | Asteraceae | |
| Lactuca saligna | willowleaf lettuce | Asteraceae | |
| Lactuca serriola | prickly lettuce | Asteraceae | |
| Lactuca tatarica | blue lettuce | Asteraceae | |
| Lactuca tatarica var. pulchella | blue lettuce | Asteraceae | |
| Laennecia | horseweed | Asteraceae | |
| Laennecia coulteri | Coulter's horseweed | Asteraceae | |
| Laennecia eriophylla | Cochise horseweed | Asteraceae | |
| Laennecia schiedeana | pineland horseweed | Asteraceae | |
| Laennecia sophiifolia | leafy horseweed | Asteraceae | |
| Lagascea | lagascea | Asteraceae | |
| Lagascea decipiens | doll's head | Asteraceae | |
| Lagenaria | lagenaria | Cucurbitaceae | |
| Lagenaria siceraria | bottle gourd | Cucurbitaceae | |
| Lamarckia | goldentop grass | Poaceae | |
| Lamarckia aurea | goldentop grass | Poaceae | |
| Lamium | deadnettle | Lamiaceae | |
| Lamium amplexicaule | henbit deadnettle | Lamiaceae | |
| Landoltia | Lemnaceae | ||
| Landoltia punctata | dotted duckmeat | Lemnaceae | |
| Langloisia | langloisia | Polemoniaceae | |
| Langloisia setosissima | Great Basin langloisia | Polemoniaceae | |
| Langloisia setosissima ssp. setosissima | Great Basin langloisia | Polemoniaceae | |
| Lantana | lantana | Verbenaceae | |
| Lantana achyranthifolia | brushland shrubverbena | Verbenaceae | |
| Lantana camara | lantana | Verbenaceae | |
| Lantana urticoides | West Indian shrubverbena | Verbenaceae | |
| Lappula | stickseed | Boraginaceae | |
| Lappula occidentalis | flatspine stickseed | Boraginaceae | |
| Lappula occidentalis var. cupulata | flatspine stickseed | Boraginaceae | |
| Lappula occidentalis var. occidentalis | flatspine stickseed | Boraginaceae | |
| Lappula squarrosa | European stickseed | Boraginaceae | |
| Lapsana | nipplewort | Asteraceae | |
| Lapsana communis | common nipplewort | Asteraceae | |
| Larrea | creosote bush | Zygophyllaceae | |
| Larrea tridentata | creosote bush | Zygophyllaceae | |
| Larrea tridentata var. tridentata | creosote bush | Zygophyllaceae | |
| Lasianthaea | lasianthaea | Asteraceae | |
| Lasianthaea podocephala | San Pedro daisy | Asteraceae | |
| Lasthenia | goldfields | Asteraceae | |
| Lasthenia californica | California goldfields | Asteraceae | |
| Lasthenia californica ssp. californica | California goldfields | Asteraceae | |
| Lathyrus | pea | Fabaceae | |
| Lathyrus brachycalyx | Bonneville pea | Fabaceae | |
| Lathyrus brachycalyx ssp. zionis | bush pea | Fabaceae | |
| Lathyrus eucosmus | bush vetchling | Fabaceae | |
| Lathyrus graminifolius | grassleaf pea | Fabaceae | |
| Lathyrus laetivirens | aspen pea | Fabaceae | |
| Lathyrus lanszwertii | Nevada pea | Fabaceae | |
| Lathyrus lanszwertii var. leucanthus | Nevada pea | Fabaceae | |
| Lathyrus latifolius | perennial pea | Fabaceae | |
| Lathyrus pauciflorus | fewflower pea | Fabaceae | |
| Lathyrus pauciflorus var. utahensis | Utah pea | Fabaceae | |
| Layia | tidytips | Asteraceae | |
| Layia glandulosa | whitedaisy tidytips | Asteraceae | |
| Layia platyglossa | coastal tidytips | Asteraceae | |
| Leersia | cutgrass | Poaceae | |
| Leersia oryzoides | rice cutgrass | Poaceae | |
| Leibnitzia | sunbonnets | Asteraceae | |
| Leibnitzia lyrata | Seeman's sunbonnets | Asteraceae | |
| Lemna | duckweed | Lemnaceae | |
| Lemna aequinoctialis | lesser duckweed | Lemnaceae | |
| Lemna gibba | swollen duckweed | Lemnaceae | |
| Lemna minor | common duckweed | Lemnaceae | |
| Lemna minuta | least duckweed | Lemnaceae | |
| Lemna obscura | little duckweed | Lemnaceae | |
| Lemna perpusilla | minute duckweed | Lemnaceae | |
| Lemna trisulca | star duckweed | Lemnaceae | |
| Lemna turionifera | turion duckweed | Lemnaceae | |
| Lemna valdiviana | valdivia duckweed | Lemnaceae | |
| Leontodon | hawkbit | Asteraceae | |
| Leontodon taraxacoides | lesser hawkbit | Asteraceae | |
| Leontodon taraxacoides ssp. taraxacoides | lesser hawkbit | Asteraceae | |
| Leonurus | motherwort | Lamiaceae | |
| Leonurus cardiaca | common motherwort | Lamiaceae | |
| Leonurus cardiaca ssp. cardiaca | common motherwort | Lamiaceae | |
| Lepidium | pepperweed | Brassicaceae | |
| Lepidium alyssoides | mesa pepperwort | Brassicaceae | |
| Lepidium alyssoides var. alyssoides | mesa pepperwort | Brassicaceae | |
| Lepidium alyssoides var. junceum | mesa pepperwort | Brassicaceae | |
| Lepidium campestre | field pepperweed | Brassicaceae | |
| Lepidium densiflorum | common pepperweed | Brassicaceae | |
| Lepidium densiflorum var. densiflorum | common pepperweed | Brassicaceae | |
| Lepidium densiflorum var. macrocarpum | bigseed pepperweed | Brassicaceae | |
| Lepidium densiflorum var. ramosum | miner's pepperweed | Brassicaceae | |
| Lepidium fremontii | desert pepperweed | Brassicaceae | |
| Lepidium fremontii var. fremontii | desert pepperweed | Brassicaceae | |
| Lepidium integrifolium | thickleaf pepperweed | Brassicaceae | |
| Lepidium integrifolium var. integrifolium | thickleaf pepperweed | Brassicaceae | |
| Lepidium lasiocarpum | shaggyfruit pepperweed | Brassicaceae | |
| Lepidium lasiocarpum var. lasiocarpum | shaggyfruit pepperweed | Brassicaceae | |
| Lepidium lasiocarpum var. wrightii | Wright's pepperweed | Brassicaceae | |
| Lepidium latifolium | broadleaved pepperweed | Brassicaceae | |
| Lepidium montanum | mountain pepperweed | Brassicaceae | |
| Lepidium montanum var. canescens | mountain pepperweed | Brassicaceae | |
| Lepidium montanum var. cinereum | mountain pepperweed | Brassicaceae | |
| Lepidium montanum var. glabrum | mountain pepperweed | Brassicaceae | |
| Lepidium montanum var. jonesii | Jones' pepperweed | Brassicaceae | |
| Lepidium montanum var. montanum | mountain pepperweed | Brassicaceae | |
| Lepidium oblongum | veiny pepperweed | Brassicaceae | |
| Lepidium oblongum var. oblongum | veiny pepperweed | Brassicaceae | |
| Lepidium perfoliatum | clasping pepperweed | Brassicaceae | |
| Lepidium ramosissimum | manybranched pepperweed | Brassicaceae | |
| Lepidium ramosissimum var. bourgeauanum | Bourgeau's pepperweed | Brassicaceae | |
| Lepidium thurberi | Thurber's pepperweed | Brassicaceae | |
| Lepidium virginicum | Virginia pepperweed | Brassicaceae | |
| Lepidium virginicum var. medium | intermediate pepperweed | Brassicaceae | |
| Lepidium virginicum var. pubescens | hairy pepperweed | Brassicaceae | |
| Lepidospartum | broomsage | Asteraceae | |
| Lepidospartum squamatum | California broomsage | Asteraceae | |
| Leptochloa | sprangletop | Poaceae | |
| Leptochloa dubia | green sprangletop | Poaceae | |
| Leptochloa fusca | Malabar sprangletop | Poaceae | |
| Leptochloa fusca ssp. fascicularis | bearded sprangletop | Poaceae | |
| Leptochloa fusca ssp. uninervia | Mexican sprangletop | Poaceae | |
| Leptochloa nealleyi | Nealley's sprangletop | Poaceae | |
| Leptochloa panicea | mucronate sprangletop | Poaceae | |
| Leptochloa panicea ssp. brachiata | mucronate sprangeltop | Poaceae | |
| Leptochloa viscida | sticky sprangletop | Poaceae | |
| Leptosiphon | Polemoniaceae | ||
| Leptosiphon aureus | golden linanthus | Polemoniaceae | |
| Leptosiphon aureus ssp. aureus | golden linanthus | Polemoniaceae | |
| Leptosiphon aureus ssp. decorus | golden linanthus | Polemoniaceae | |
| Leptosiphon floribundum | many-flower linanthus | Polemoniaceae | |
| Leptosiphon floribundum ssp. floribundum | manyflower linanthus | Polemoniaceae | |
| Leptosiphon nuttallii | Nuttall's linanthus | Polemoniaceae | |
| Leptosiphon nuttallii ssp. tenuilobus | Nuttall's linanthus | Polemoniaceae | |
| Lesquerella | bladderpod | Brassicaceae | |
| Lesquerella arizonica | Arizona bladderpod | Brassicaceae | |
| Lesquerella cinerea | basin bladderpod | Brassicaceae | |
| Lesquerella fendleri | Fendler's bladderpod | Brassicaceae | |
| Lesquerella gooddingii | Goodding's bladderpod | Brassicaceae | |
| Lesquerella gordonii | Gordon's bladderpod | Brassicaceae | |
| Lesquerella gordonii var. gordonii | Gordon's bladderpod | Brassicaceae | |
| Lesquerella intermedia | mid bladderpod | Brassicaceae | |
| Lesquerella kaibabensis | Kaibab bladderpod | Brassicaceae | |
| Lesquerella ludoviciana | foothill bladderpod | Brassicaceae | |
| Lesquerella pinetorum | White Mountain bladderpod | Brassicaceae | |
| Lesquerella purpurea | rose bladderpod | Brassicaceae | |
| Lesquerella rectipes | straight bladderpod | Brassicaceae | |
| Lesquerella tenella | Moapa bladderpod | Brassicaceae | |
| Lesquerella wardii | Ward's bladderpod | Brassicaceae | |
| Lessingia | lessingia | Asteraceae | |
| Lessingia lemmonii | Lemmon's lessingia | Asteraceae | |
| Lessingia lemmonii var. lemmonii | Lemmon's lessingia | Asteraceae | |
| Leucaena | leadtree | Fabaceae | |
| Leucaena leucocephala | white leadtree | Fabaceae | |
| Leucaena leucocephala ssp. glabrata | Fabaceae | ||
| Leucanthemum | daisy | Asteraceae | |
| Leucanthemum vulgare | oxeye daisy | Asteraceae | |
| Leuciva | Asteraceae | ||
| Leuciva dealbata | woolly marsh elder | Asteraceae | |
| Leucocrinum | starlily | Liliaceae | |
| Leucocrinum montanum | common starlily | Liliaceae | |
| Lewisia | lewisia | Portulacaceae | |
| Lewisia brachycalyx | shortsepal lewisia | Portulacaceae | |
| Lewisia nevadensis | Nevada lewisia | Portulacaceae | |
| Lewisia pygmaea | alpine lewisia | Portulacaceae | |
| Lewisia rediviva | bitter root | Portulacaceae | |
| Lewisia rediviva var. rediviva | bitter root | Portulacaceae | |
| Leymus | wildrye | Poaceae | |
| Leymus cinereus | basin wildrye | Poaceae | |
| Leymus racemosus | mammoth wildrye | Poaceae | |
| Leymus salinus | saline wildrye | Poaceae | |
| Leymus salinus ssp. mojavensis | Mojave wildrye | Poaceae | |
| Leymus salinus ssp. salinus | saline wildrye | Poaceae | |
| Leymus simplex | alkali wildrye | Poaceae | |
| Leymus triticoides | beardless wildrye | Poaceae | |
| Ligusticum | licorice-root | Apiaceae | |
| Ligusticum porteri | Porter's licorice-root | Apiaceae | |
| Ligusticum porteri var. porteri | Porter's licorice-root | Apiaceae | |
| Lilaeopsis | grasswort | Apiaceae | |
| Lilaeopsis schaffneriana | Schaffner's grasswort | Apiaceae | |
| Lilaeopsis schaffneriana var. recurva | Schaffner's grasswort | Apiaceae | |
| Lilium | lily | Liliaceae | |
| Lilium parryi | lemon lily | Liliaceae | |
| Lilium philadelphicum | wood lily | Liliaceae | |
| Lilium philadelphicum var. andinum | wood lily | Liliaceae | |
| Limonium | sea lavender | Plumbaginaceae | |
| Limonium limbatum | Trans-Pecos sea lavender | Plumbaginaceae | |
| Limosella | mudwort | Scrophulariaceae | |
| Limosella acaulis | Owyhee mudwort | Scrophulariaceae | |
| Limosella aquatica | water mudwort | Scrophulariaceae | |
| Limosella pubiflora | Chiricahua Mountain mudwort | Scrophulariaceae | |
| Linanthus | linanthus | Polemoniaceae | |
| Linanthus bigelovii | Bigelow's linanthus | Polemoniaceae | |
| Linanthus demissus | desertsnow | Polemoniaceae | |
| Linanthus dichotomus | eveningsnow | Polemoniaceae | |
| Linanthus filiformis | yellow gilia | Polemoniaceae | |
| Linanthus jonesii | Jones' linanthus | Polemoniaceae | |
| Linanthus pungens | granite prickly phlox | Polemoniaceae | |
| Linaria | toadflax | Scrophulariaceae | |
| Linaria dalmatica | Dalmatian toadflax | Scrophulariaceae | |
| Linaria dalmatica ssp. dalmatica | Dalmatian toadflax | Scrophulariaceae | |
| Linaria maroccana | Moroccan toadflax | Scrophulariaceae | |
| Linaria vulgaris | butter and eggs | Scrophulariaceae | |
| Lindernia | false pimpernel | Scrophulariaceae | |
| Lindernia dubia | yellowseed false pimpernel | Scrophulariaceae | |
| Lindernia dubia var. anagallidea | yellowseed false pimpernel | Scrophulariaceae | |
| Lindernia dubia var. dubia | yellowseed false pimpernel | Scrophulariaceae | |
| Linnaea | twinflower | Caprifoliaceae | |
| Linnaea borealis | twinflower | Caprifoliaceae | |
| Linnaea borealis ssp. americana | twinflower | Caprifoliaceae | |
| Linum | flax | Linaceae | |
| Linum aristatum | bristle flax | Linaceae | |
| Linum australe | southern flax | Linaceae | |
| Linum australe var. australe | southern flax | Linaceae | |
| Linum australe var. glandulosum | southern flax | Linaceae | |
| Linum lewisii | Lewis flax | Linaceae | |
| Linum lewisii var. lewisii | prairie flax | Linaceae | |
| Linum neomexicanum | New Mexico yellow flax | Linaceae | |
| Linum pratense | meadow flax | Linaceae | |
| Linum puberulum | plains flax | Linaceae | |
| Linum subteres | sprucemont flax | Linaceae | |
| Linum usitatissimum | common flax | Linaceae | |
| Lipocarpha | halfchaff sedge | Cyperaceae | |
| Lipocarpha aristulata | awned halfchaff sedge | Cyperaceae | |
| Lipocarpha drummondii | Drummond's halfchaff sedge | Cyperaceae | |
| Lipocarpha micrantha | smallflower halfchaff sedge | Cyperaceae | |
| Listera | twayblade | Orchidaceae | |
| Listera convallarioides | broadlipped twayblade | Orchidaceae | |
| Lithophragma | woodland-star | Saxifragaceae | |
| Lithophragma tenellum | slender woodland-star | Saxifragaceae | |
| Lithospermum | stoneseed | Boraginaceae | |
| Lithospermum cobrense | smooththroat stoneseed | Boraginaceae | |
| Lithospermum confine | Arizona stoneseed | Boraginaceae | |
| Lithospermum incisum | narrowleaf stoneseed | Boraginaceae | |
| Lithospermum multiflorum | manyflowered stoneseed | Boraginaceae | |
| Lithospermum obtusifolium | roundleaf stoneseed | Boraginaceae | |
| Lithospermum viride | green stoneseed | Boraginaceae | |
| Lobelia | lobelia | Campanulaceae | |
| Lobelia anatina | Apache lobelia | Campanulaceae | |
| Lobelia cardinalis | cardinalflower | Campanulaceae | |
| Lobelia fenestralis | fringeleaf lobelia | Campanulaceae | |
| Lobelia laxiflora | Sierra Madre lobelia | Campanulaceae | |
| Lobelia laxiflora var. angustifolia | Sierra Madre lobelia | Campanulaceae | |
| Lobularia | lobularia | Brassicaceae | |
| Lobularia maritima | sweet alyssum | Brassicaceae | |
| Loeflingia | loeflingia | Caryophyllaceae | |
| Loeflingia squarrosa | spreading pygmyleaf | Caryophyllaceae | |
| Loeflingia squarrosa ssp. cactorum | spreading pygmyleaf | Caryophyllaceae | |
| Loeflingia squarrosa ssp. squarrosa | spreading pygmyleaf | Caryophyllaceae | |
| Loeselia | false calico | Polemoniaceae | |
| Loeselia glandulosa | glandular false calico | Polemoniaceae | |
| Loeseliastrum | calico | Polemoniaceae | |
| Loeseliastrum schottii | Schott's calico | Polemoniaceae | |
| Logfia | cottonrose | Asteraceae | |
| Logfia arizonica | Arizona cottonrose | Asteraceae | |
| Logfia californica | California cottonrose | Asteraceae | |
| Logfia depressa | dwarf cottonrose | Asteraceae | |
| Lolium | ryegrass | Poaceae | |
| Lolium perenne | perennial ryegrass | Poaceae | |
| Lolium perenne ssp. multiflorum | Italian ryegrass | Poaceae | |
| Lolium perenne ssp. perenne | perennial ryegrass | Poaceae | |
| Lolium rigidum | Wimmera ryegrass | Poaceae | |
| Lolium temulentum | Darnel ryegrass | Poaceae | |
| Lolium temulentum ssp. temulentum | Darnel ryegrass | Poaceae | |
| Lomatium | desertparsley | Apiaceae | |
| Lomatium bicolor | Wasatch desertparsley | Apiaceae | |
| Lomatium bicolor var. leptocarpum | Wasatch desertparsley | Apiaceae | |
| Lomatium dissectum | fernleaf biscuitroot | Apiaceae | |
| Lomatium dissectum var. multifidum | carrotleaf biscuitroot | Apiaceae | |
| Lomatium foeniculaceum | desert biscuitroot | Apiaceae | |
| Lomatium foeniculaceum ssp. macdougalii | Macdougal's biscuitroot | Apiaceae | |
| Lomatium mohavense | Mojave desertparsley | Apiaceae | |
| Lomatium mohavense ssp. mohavense | Mojave desertparsley | Apiaceae | |
| Lomatium nevadense | Nevada biscuitroot | Apiaceae | |
| Lomatium nevadense var. nevadense | Nevada biscuitroot | Apiaceae | |
| Lomatium nevadense var. parishii | Parish's biscuitroot | Apiaceae | |
| Lomatium orientale | Northern Idaho biscuitroot | Apiaceae | |
| Lomatium parryi | Utah desertparsley | Apiaceae | |
| Lomatium scabrum | rough desertparsley | Apiaceae | |
| Lomatium scabrum var. tripinnatum | rough desertparsley | Apiaceae | |
| Lomatium simplex | Great Basin desertparsley | Apiaceae | |
| Lomatium simplex var. simplex | Great Basin desertparsley | Apiaceae | |
| Lonicera | honeysuckle | Caprifoliaceae | |
| Lonicera albiflora | western white honeysuckle | Caprifoliaceae | |
| Lonicera arizonica | Arizona honeysuckle | Caprifoliaceae | |
| Lonicera ciliosa | orange honeysuckle | Caprifoliaceae | |
| Lonicera interrupta | chaparral honeysuckle | Caprifoliaceae | |
| Lonicera involucrata | twinberry honeysuckle | Caprifoliaceae | |
| Lonicera involucrata var. involucrata | twinberry honeysuckle | Caprifoliaceae | |
| Lonicera japonica | Japanese honeysuckle | Caprifoliaceae | |
| Lonicera utahensis | Utah honeysuckle | Caprifoliaceae | |
| Lotus | trefoil | Fabaceae | |
| Lotus alamosanus | Sonoran bird's-foot trefoil | Fabaceae | |
| Lotus corniculatus | bird's-foot trefoil | Fabaceae | |
| Lotus corniculatus var. corniculatus | bird's-foot trefoil | Fabaceae | |
| Lotus greenei | Greene's bird's-foot trefoil | Fabaceae | |
| Lotus hamatus | San Diego bird's-foot trefoil | Fabaceae | |
| Lotus humistratus | foothill deervetch | Fabaceae | |
| Lotus mearnsii | Mearns' bird's-foot trefoil | Fabaceae | |
| Lotus mearnsii var. equisolensis | Mearns' bird's-foot trefoil | Fabaceae | |
| Lotus mearnsii var. mearnsii | Mearns' bird's-foot trefoil | Fabaceae | |
| Lotus oblongifolius | streambank bird's-foot trefoil | Fabaceae | |
| Lotus oblongifolius var. oblongifolius | streambank bird's-foot trefoil | Fabaceae | |
| Lotus plebeius | New Mexico bird's-foot trefoil | Fabaceae | |
| Lotus rigidus | shrubby deervetch | Fabaceae | |
| Lotus salsuginosus | coastal bird's-foot trefoil | Fabaceae | |
| Lotus salsuginosus var. brevivexillus | coastal bird's-foot trefoil | Fabaceae | |
| Lotus scoparius | common deerweed | Fabaceae | |
| Lotus scoparius var. brevialatus | western bird's-foot trefoil | Fabaceae | |
| Lotus strigosus | strigose bird's-foot trefoil | Fabaceae | |
| Lotus strigosus var. tomentellus | strigose bird's-foot trefoil | Fabaceae | |
| Lotus unifoliolatus | American bird's-foot trefoil | Fabaceae | |
| Lotus unifoliolatus var. unifoliolatus | American bird's-foot trefoil | Fabaceae | |
| Lotus utahensis | Utah bird's-foot trefoil | Fabaceae | |
| Lotus wrightii | Wright's deervetch | Fabaceae | |
| Ludwigia | primrose-willow | Onagraceae | |
| Ludwigia palustris | marsh seedbox | Onagraceae | |
| Ludwigia peploides | floating primrose-willow | Onagraceae | |
| Ludwigia peploides ssp. peploides | floating primrose-willow | Onagraceae | |
| Ludwigia repens | creeping primrose-willow | Onagraceae | |
| Lupinus | lupine | Fabaceae | |
| Lupinus alpestris | Great Basin lupine | Fabaceae | |
| Lupinus ammophilus | sand lupine | Fabaceae | |
| Lupinus argenteus | silvery lupine | Fabaceae | |
| Lupinus argenteus ssp. argenteus | silvery lupine | Fabaceae | |
| Lupinus argenteus ssp. argenteus var. argenteus | silvery lupine | Fabaceae | |
| Lupinus argenteus ssp. argenteus var. laxiflorus | silvery lupine | Fabaceae | |
| Lupinus aridus | desert lupine | Fabaceae | |
| Lupinus aridus ssp. aridus | desert lupine | Fabaceae | |
| Lupinus arizonicus | Arizona lupine | Fabaceae | |
| Lupinus arizonicus ssp. arizonicus | Arizona lupine | Fabaceae | |
| Lupinus arizonicus ssp. arizonicus var. arizonicus | Arizona lupine | Fabaceae | |
| Lupinus arizonicus ssp. arizonicus var. barbatulus | Arizona lupine | Fabaceae | |
| Lupinus arizonicus ssp. setosissimus | Arizona lupine | Fabaceae | |
| Lupinus arizonicus ssp. sonorensis | Sonora lupine | Fabaceae | |
| Lupinus barbiger | bearded lupine | Fabaceae | |
| Lupinus bicolor | miniature lupine | Fabaceae | |
| Lupinus bicolor ssp. microphyllus | miniature lupine | Fabaceae | |
| Lupinus bicolor ssp. pipersmithii | miniature lupine | Fabaceae | |
| Lupinus brevicaulis | shortstem lupine | Fabaceae | |
| Lupinus caudatus | tailcup lupine | Fabaceae | |
| Lupinus caudatus ssp. argophyllus | Kellogg's spurred lupine | Fabaceae | |
| Lupinus caudatus ssp. caudatus | tailcup lupine | Fabaceae | |
| Lupinus caudatus ssp. cutleri | Cutler's spurred lupine | Fabaceae | |
| Lupinus chihuahuensis | Chihuahuan lupine | Fabaceae | |
| Lupinus concinnus | bajada lupine | Fabaceae | |
| Lupinus concinnus ssp. orcuttii | Orcutt's lupine | Fabaceae | |
| Lupinus flavoculatus | yelloweyes | Fabaceae | |
| Lupinus hillii | Hill's lupine | Fabaceae | |
| Lupinus hillii var. arizonicus | Hill's lupine | Fabaceae | |
| Lupinus hillii var. hillii | Hill's lupine | Fabaceae | |
| Lupinus hillii var. osterhoutianus | Osterhout's lupine | Fabaceae | |
| Lupinus huachucanus | Huachuca Mountain lupine | Fabaceae | |
| Lupinus kingii | King's lupine | Fabaceae | |
| Lupinus kingii var. kingii | King's lupine | Fabaceae | |
| Lupinus latifolius | broadleaf lupine | Fabaceae | |
| Lupinus latifolius ssp. leucanthus | broadleaf lupine | Fabaceae | |
| Lupinus lemmonii | Lemmon's lupine | Fabaceae | |
| Lupinus neomexicanus | New Mexico lupine | Fabaceae | |
| Lupinus odoratus | Mojave lupine | Fabaceae | |
| Lupinus odoratus var. odoratus | Mojave lupine | Fabaceae | |
| Lupinus odoratus var. pilosellus | Mojave lupine | Fabaceae | |
| Lupinus palmeri | bluebonnet lupine | Fabaceae | |
| Lupinus pusillus | rusty lupine | Fabaceae | |
| Lupinus pusillus ssp. intermontanus | Intermountain lupine | Fabaceae | |
| Lupinus pusillus ssp. pusillus | rusty lupine | Fabaceae | |
| Lupinus pusillus ssp. rubens | rusty lupine | Fabaceae | |
| Lupinus sericeus | silky lupine | Fabaceae | |
| Lupinus sericeus ssp. huffmanii | silky lupine | Fabaceae | |
| Lupinus sericeus ssp. sericeus | silky lupine | Fabaceae | |
| Lupinus sericeus ssp. sericeus var. sericeus | silky lupine | Fabaceae | |
| Lupinus shockleyi | purple desert lupine | Fabaceae | |
| Lupinus sparsiflorus | Coulter's lupine | Fabaceae | |
| Lupinus sparsiflorus ssp. mohavensis | Coulter's lupine | Fabaceae | |
| Lupinus succulentus | hollowleaf annual lupine | Fabaceae | |
| Lupinus volutans | pinyon lupine | Fabaceae | |
| Luzula | woodrush | Juncaceae | |
| Luzula multiflora | common woodrush | Juncaceae | |
| Luzula multiflora ssp. frigida | common woodrush | Juncaceae | |
| Luzula parviflora | smallflowered woodrush | Juncaceae | |
| Luzula spicata | spiked woodrush | Juncaceae | |
| Lycium | desert-thorn | Solanaceae | |
| Lycium andersonii | water jacket | Solanaceae | |
| Lycium andersonii var. andersonii | water jacket | Solanaceae | |
| Lycium andersonii var. deserticola | water jacket | Solanaceae | |
| Lycium andersonii var. wrightii | water jacket | Solanaceae | |
| Lycium berlandieri | Berlandier's wolfberry | Solanaceae | |
| Lycium berlandieri var. longistylum | Berlandier's wolfberry | Solanaceae | |
| Lycium berlandieri var. parviflorum | Berlandier's wolfberry | Solanaceae | |
| Lycium brevipes | Baja desert-thorn | Solanaceae | |
| Lycium californicum | California desert-thorn | Solanaceae | |
| Lycium californicum var. arizonicum | Solanaceae | ||
| Lycium cooperi | peach thorn | Solanaceae | |
| Lycium exsertum | Arizona desert-thorn | Solanaceae | |
| Lycium fremontii | Fremont's desert-thorn | Solanaceae | |
| Lycium macrodon | desert wolfberry | Solanaceae | |
| Lycium pallidum | pale desert-thorn | Solanaceae | |
| Lycium pallidum var. pallidum | pale desert-thorn | Solanaceae | |
| Lycium parishii | Parish's desert-thorn | Solanaceae | |
| Lycium torreyi | Torrey wolfberry | Solanaceae | |
| Lycopodium | clubmoss | Lycopodiaceae | |
| Lycopodium annotinum | stiff clubmoss | Lycopodiaceae | |
| Lycopus | waterhorehound | Lamiaceae | |
| Lycopus americanus | American water horehound | Lamiaceae | |
| Lycopus asper | rough bugleweed | Lamiaceae | |
| Lycurus | wolfstail | Poaceae | |
| Lycurus phleoides | common wolfstail | Poaceae | |
| Lycurus setosus | bristly wolfstail | Poaceae | |
| Lygodesmia | skeletonplant | Asteraceae | |
| Lygodesmia arizonica | Arizona skeletonplant | Asteraceae | |
| Lygodesmia grandiflora | largeflower skeletonplant | Asteraceae | |
| Lygodesmia juncea | rush skeletonplant | Asteraceae | |
| Lyrocarpa | lyrepod | Brassicaceae | |
| Lyrocarpa coulteri | Coulter's lyrepod | Brassicaceae | |
| Lyrocarpa coulteri var. coulteri | Coulter's lyrepod | Brassicaceae | |
| Lysiloma | false tamarind | Fabaceae | |
| Lysiloma watsonii | littleleaf false tamarind | Fabaceae | |
| Lysimachia | yellow loosestrife | Primulaceae | |
| Lysimachia hybrida | lowland yellow loosestrife | Primulaceae | |
| Lythrum | loosestrife | Lythraceae | |
| Lythrum californicum | California loosestrife | Lythraceae | |
| M | |||
| Mabrya | mabrya | Scrophulariaceae | |
| Mabrya acerifolia | brittlestem | Scrophulariaceae | |
| Machaeranthera | tansyaster | Asteraceae | |
| Machaeranthera arida | arid tansyaster | Asteraceae | |
| Machaeranthera asteroides | fall tansyaster | Asteraceae | |
| Machaeranthera asteroides var. asteroides | fall tansyaster | Asteraceae | |
| Machaeranthera asteroides var. glandulosa | Asteraceae | ||
| Machaeranthera bigelovii | Bigelow's tansyaster | Asteraceae | |
| Machaeranthera bigelovii var. mucronata | Bigelow's tansyaster | Asteraceae | |
| Machaeranthera canescens | hoary tansyaster | Asteraceae | |
| Machaeranthera canescens ssp. canescens | hoary tansyaster | Asteraceae | |
| Machaeranthera canescens ssp. canescens var. ambigua | hoary tansyaster | Asteraceae | |
| Machaeranthera canescens ssp. canescens var. canescens | hoary tansyaster | Asteraceae | |
| Machaeranthera canescens ssp. glabra | hoary tansyaster | Asteraceae | |
| Machaeranthera canescens ssp. glabra var. aristata | hoary tansyaster | Asteraceae | |
| Machaeranthera canescens ssp. glabra var. glabra | hoary tansyaster | Asteraceae | |
| Machaeranthera carnosa | shrubby alkaliaster | Asteraceae | |
| Machaeranthera carnosa var. carnosa | shrubby alkaliaster | Asteraceae | |
| Machaeranthera gracilis | slender goldenweed | Asteraceae | |
| Machaeranthera grindelioides | rayless tansyaster | Asteraceae | |
| Machaeranthera grindelioides var. depressa | rayless tansyaster | Asteraceae | |
| Machaeranthera grindelioides var. grindelioides | rayless tansyaster | Asteraceae | |
| Machaeranthera juncea | rush bristleweed | Asteraceae | |
| Machaeranthera parviflora | smallflower tansyaster | Asteraceae | |
| Machaeranthera pinnatifida | lacy tansyaster | Asteraceae | |
| Machaeranthera pinnatifida ssp. gooddingii | Goodding's tansyaster | Asteraceae | |
| Machaeranthera pinnatifida ssp. gooddingii var. gooddingii | Goodding's tansyaster | Asteraceae | |
| Machaeranthera pinnatifida ssp. gooddingii var. paradoxa | Goodding's tansyaster | Asteraceae | |
| Machaeranthera pinnatifida ssp. pinnatifida | lacy tansyaster | Asteraceae | |
| Machaeranthera pinnatifida ssp. pinnatifida var. chihuahuana | Chihuahua tansyaster | Asteraceae | |
| Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | lacy tansyaster | Asteraceae | |
| Machaeranthera riparia | Chiricahua Mountain tansyaster | Asteraceae | |
| Machaeranthera tagetina | mesa tansyaster | Asteraceae | |
| Machaeranthera tanacetifolia | tanseyleaf tansyaster | Asteraceae | |
| Macromeria | giant-trumpets | Boraginaceae | |
| Macromeria viridiflora | giant-trumpets | Boraginaceae | |
| Macromeria viridiflora var. thurberi | Thurber's giant-trumpets | Boraginaceae | |
| Macromeria viridiflora var. viridiflora | giant-trumpets | Boraginaceae | |
| Macroptilium | bushbean | Fabaceae | |
| Macroptilium atropurpureum | purple bushbean | Fabaceae | |
| Macroptilium gibbosifolium | variableleaf bushbean | Fabaceae | |
| Macroptilium supinum | supine bean | Fabaceae | |
| Macrosiphonia | rocktrumpet | Apocynaceae | |
| Macrosiphonia brachysiphon | Huachuca Mountain rocktrumpet | Apocynaceae | |
| Madia | tarweed | Asteraceae | |
| Madia glomerata | mountain tarweed | Asteraceae | |
| Mahonia | barberry | Berberidaceae | |
| Mahonia fremontii | Fremont's mahonia | Berberidaceae | |
| Mahonia haematocarpa | red barberry | Berberidaceae | |
| Mahonia repens | creeping barberry | Berberidaceae | |
| Mahonia trifoliolata | algerita | Berberidaceae | |
| Maianthemum | mayflower | Liliaceae | |
| Maianthemum racemosum | feathery false lily of the valley | Liliaceae | |
| Maianthemum racemosum ssp. amplexicaule | feathery false lily of the valley | Liliaceae | |
| Maianthemum stellatum | starry false lily of the valley | Liliaceae | |
| Malacothrix | desertdandelion | Asteraceae | |
| Malacothrix clevelandii | Cleveland's desertdandelion | Asteraceae | |
| Malacothrix coulteri | snake's head | Asteraceae | |
| Malacothrix fendleri | Fendler's desertdandelion | Asteraceae | |
| Malacothrix glabrata | smooth desertdandelion | Asteraceae | |
| Malacothrix sonchoides | sowthistle desertdandelion | Asteraceae | |
| Malacothrix sonorae | Sonoran desertdandelion | Asteraceae | |
| Malacothrix stebbinsii | Stebbins' desertdandelion | Asteraceae | |
| Malacothrix torreyi | Torrey's desertdandelion | Asteraceae | |
| Malaxis | adder's-mouth orchid | Orchidaceae | |
| Malaxis corymbosa | Huachuca Mountain adder's-mouth orchid | Orchidaceae | |
| Malaxis porphyrea | Cochise adder's-mouth orchid | Orchidaceae | |
| Malaxis soulei | Chiricahua adder's-mouth orchid | Orchidaceae | |
| Malaxis tenuis | Arizona adder's-mouth orchid | Orchidaceae | |
| Malcolmia | malcolmia | Brassicaceae | |
| Malcolmia africana | African mustard | Brassicaceae | |
| Malva | mallow | Malvaceae | |
| Malva neglecta | common mallow | Malvaceae | |
| Malva parviflora | cheeseweed mallow | Malvaceae | |
| Malva sylvestris | high mallow | Malvaceae | |
| Malvastrum | false mallow | Malvaceae | |
| Malvastrum bicuspidatum | shrubby false mallow | Malvaceae | |
| Malvella | mallow | Malvaceae | |
| Malvella lepidota | scurfymallow | Malvaceae | |
| Malvella leprosa | alkali mallow | Malvaceae | |
| Malvella sagittifolia | arrowleaf mallow | Malvaceae | |
| Mammillaria | globe cactus | Cactaceae | |
| Mammillaria barbata | greenflower nipple cactus | Cactaceae | |
| Mammillaria grahamii | Graham's nipple cactus | Cactaceae | |
| Mammillaria heyderi | little nipple cactus | Cactaceae | |
| Mammillaria heyderi var. bullingtoniana | little nipple cactus | Cactaceae | |
| Mammillaria heyderi var. heyderi | little nipple cactus | Cactaceae | |
| Mammillaria heyderi var. macdougalii | Macdougal's nipple cactus | Cactaceae | |
| Mammillaria heyderi var. meiacantha | little nipple cactus | Cactaceae | |
| Mammillaria lasiacantha | lacespine nipple cactus | Cactaceae | |
| Mammillaria mainiae | counterclockwise nipple cactus | Cactaceae | |
| Mammillaria tetrancistra | common fishhook cactus | Cactaceae | |
| Mammillaria thornberi | Thornber's nipple cactus | Cactaceae | |
| Mammillaria wrightii | Wright's nipple cactus | Cactaceae | |
| Mammillaria wrightii var. wilcoxii | Wilcox's nipple cactus | Cactaceae | |
| Mammillaria wrightii var. wrightii | Wright's nipple cactus | Cactaceae | |
| Manihot | cassava | Euphorbiaceae | |
| Manihot angustiloba | desertmountain manihot | Euphorbiaceae | |
| Manihot davisiae | Arizona manihot | Euphorbiaceae | |
| Mantisalca | mantisalca | Asteraceae | |
| Mantisalca salmantica | dagger flower | Asteraceae | |
| Marah | manroot | Cucurbitaceae | |
| Marah gilensis | Gila manroot | Cucurbitaceae | |
| Margaranthus | margaranthus | Solanaceae | |
| Margaranthus solanaceus | netted globecherry | Solanaceae | |
| Marina | false prairie-clover | Fabaceae | |
| Marina calycosa | San Pedro false prairie-clover | Fabaceae | |
| Marina diffusa | spreading false prairie-clover | Fabaceae | |
| Marina parryi | Parry's false prairie-clover | Fabaceae | |
| Marrubium | horehound | Lamiaceae | |
| Marrubium vulgare | horehound | Lamiaceae | |
| Marsilea | waterclover | Marsileaceae | |
| Marsilea mollis | Chihuahuan waterclover | Marsileaceae | |
| Marsilea vestita | hairy waterclover | Marsileaceae | |
| Matelea | milkvine | Asclepiadaceae | |
| Matelea arizonica | Arizona milkvine | Asclepiadaceae | |
| Matelea balbisii | Balbis' milkvine | Asclepiadaceae | |
| Matelea cordifolia | Sonoran milkvine | Asclepiadaceae | |
| Matelea parvifolia | spearleaf | Asclepiadaceae | |
| Matelea producta | Texas milkvine | Asclepiadaceae | |
| Matricaria | mayweed | Asteraceae | |
| Matricaria courrantiana | crown mayweed | Asteraceae | |
| Matricaria discoidea | disc mayweed | Asteraceae | |
| Matricaria recutita | German chamomile | Asteraceae | |
| Matthiola | stock | Brassicaceae | |
| Matthiola longipetala | night scented stock | Brassicaceae | |
| Maurandella | maurandella | Scrophulariaceae | |
| Maurandella antirrhiniflora | roving sailor | Scrophulariaceae | |
| Mecardonia | mecardonia | Scrophulariaceae | |
| Mecardonia procumbens | baby jump-up | Scrophulariaceae | |
| Medicago | alfalfa | Fabaceae | |
| Medicago lupulina | black medick | Fabaceae | |
| Medicago minima | little bur-clover | Fabaceae | |
| Medicago polymorpha | burclover | Fabaceae | |
| Medicago sativa | alfalfa | Fabaceae | |
| Medicago sativa ssp. falcata | yellow alfalfa | Fabaceae | |
| Medicago sativa ssp. sativa | alfalfa | Fabaceae | |
| Melampodium | blackfoot | Asteraceae | |
| Melampodium leucanthum | plains blackfoot | Asteraceae | |
| Melampodium longicorne | Arizona blackfoot | Asteraceae | |
| Melampodium strigosum | shaggy blackfoot | Asteraceae | |
| Melia | melia | Meliaceae | |
| Melia azedarach | Chinaberrytree | Meliaceae | |
| Melica | melicgrass | Poaceae | |
| Melica frutescens | woody melicgrass | Poaceae | |
| Melica imperfecta | smallflower melicgrass | Poaceae | |
| Melica nitens | threeflower melicgrass | Poaceae | |
| Melica porteri | Porter's melicgrass | Poaceae | |
| Melica porteri var. laxa | Porter's melicgrass | Poaceae | |
| Melica porteri var. porteri | Porter's melicgrass | Poaceae | |
| Melilotus | sweetclover | Fabaceae | |
| Melilotus indicus | annual yellow sweetclover | Fabaceae | |
| Melilotus officinalis | yellow sweetclover | Fabaceae | |
| Melinis | stinkgrass | Poaceae | |
| Melinis repens | rose Natal grass | Poaceae | |
| Menodora | menodora | Oleaceae | |
| Menodora scabra | rough menodora | Oleaceae | |
| Menodora spinescens | spiny menodora | Oleaceae | |
| Mentha | mint | Lamiaceae | |
| Mentha arvensis | wild mint | Lamiaceae | |
| Mentha rotundifolia | Lamiaceae | ||
| Mentha spicata | spearmint | Lamiaceae | |
| Mentha suaveolens | apple mint | Lamiaceae | |
| Mentzelia | blazingstar | Loasaceae | |
| Mentzelia affinis | yellowcomet | Loasaceae | |
| Mentzelia albicaulis | whitestem blazingstar | Loasaceae | |
| Mentzelia aspera | tropical blazingstar | Loasaceae | |
| Mentzelia asperula | Organ Mountain blazingstar | Loasaceae | |
| Mentzelia collomiae | Sunset Crater blazingstar | Loasaceae | |
| Mentzelia cronquistii | Cronquist's blazingstar | Loasaceae | |
| Mentzelia desertorum | desert blazingstar | Loasaceae | |
| Mentzelia incisa | streambank blazingstar | Loasaceae | |
| Mentzelia involucrata | whitebract blazingstar | Loasaceae | |
| Mentzelia involucrata var. involucrata | whitebract blazingstar | Loasaceae | |
| Mentzelia isolata | isolated blazingstar | Loasaceae | |
| Mentzelia jonesii | Jones' blazingstar | Loasaceae | |
| Mentzelia lindheimeri | Lindheimer's blazingstar | Loasaceae | |
| Mentzelia lindleyi | Lindley's blazingstar | Loasaceae | |
| Mentzelia montana | variegated-bract blazingstar | Loasaceae | |
| Mentzelia multiflora | Adonis blazingstar | Loasaceae | |
| Mentzelia multiflora var. integra | Adonis blazingstar | Loasaceae | |
| Mentzelia multiflora var. longiloba | Adonis blazingstar | Loasaceae | |
| Mentzelia multiflora var. multiflora | Adonis blazingstar | Loasaceae | |
| Mentzelia nuda | bractless blazingstar | Loasaceae | |
| Mentzelia nuda var. stricta | bractless blazingstar | Loasaceae | |
| Mentzelia obscura | Pacific blazingstar | Loasaceae | |
| Mentzelia oligosperma | chickenthief | Loasaceae | |
| Mentzelia oreophila | Argus blazingstar | Loasaceae | |
| Mentzelia polita | polished blazingstar | Loasaceae | |
| Mentzelia pterosperma | wingseed blazingstar | Loasaceae | |
| Mentzelia pumila | dwarf mentzelia | Loasaceae | |
| Mentzelia pumila var. pumila | dwarf mentzelia | Loasaceae | |
| Mentzelia rusbyi | Rusby's blazingstar | Loasaceae | |
| Mentzelia tricuspis | spinyhair blazingstar | Loasaceae | |
| Mentzelia veatchiana | Veatch's blazingstar | Loasaceae | |
| Menyanthes | buckbean | Menyanthaceae | |
| Menyanthes trifoliata | buckbean | Menyanthaceae | |
| Mertensia | bluebells | Boraginaceae | |
| Mertensia arizonica | aspen bluebells | Boraginaceae | |
| Mertensia ciliata | tall fringed bluebells | Boraginaceae | |
| Mertensia ciliata var. ciliata | tall fringed bluebells | Boraginaceae | |
| Mertensia franciscana | Franciscan bluebells | Boraginaceae | |
| Mertensia macdougalii | Macdougal's bluebells | Boraginaceae | |
| Mesembryanthemum | iceplant | Aizoaceae | |
| Mesembryanthemum crystallinum | common iceplant | Aizoaceae | |
| Mesembryanthemum nodiflorum | slenderleaf iceplant | Aizoaceae | |
| Microchloa | smallgrass | Poaceae | |
| Microchloa kunthii | Kunth's smallgrass | Poaceae | |
| Microseris | silverpuffs | Asteraceae | |
| Microseris heterocarpa | grassland silverpuffs | Asteraceae | |
| Microseris lindleyi | Lindley's silverpuffs | Asteraceae | |
| Microsteris | Polemoniaceae | ||
| Microsteris gracilis | slender phlox | Polemoniaceae | |
| Microsteris gracilis var. gracilis | slender phlox | Polemoniaceae | |
| Microsteris gracilis var. humilior | slender phlox | Polemoniaceae | |
| Milla | milla | Liliaceae | |
| Milla biflora | Mexican star | Liliaceae | |
| Mimetanthe | mimetanthe | Scrophulariaceae | |
| Mimetanthe pilosa | false monkeyflower | Scrophulariaceae | |
| Mimosa | sensitive plant | Fabaceae | |
| Mimosa aculeaticarpa | catclaw mimosa | Fabaceae | |
| Mimosa aculeaticarpa var. biuncifera | catclaw mimosa | Fabaceae | |
| Mimosa distachya | Mexican mimosa | Fabaceae | |
| Mimosa distachya var. laxiflora | Arizona mimosa | Fabaceae | |
| Mimosa dysocarpa | velvetpod mimosa | Fabaceae | |
| Mimosa grahamii | Graham's mimosa | Fabaceae | |
| Mimulus | monkeyflower | Scrophulariaceae | |
| Mimulus bigelovii | Bigelow's monkeyflower | Scrophulariaceae | |
| Mimulus bigelovii var. bigelovii | Bigelow's monkeyflower | Scrophulariaceae | |
| Mimulus cardinalis | scarlet monkeyflower | Scrophulariaceae | |
| Mimulus dentilobus | toothpetal monkeyflower | Scrophulariaceae | |
| Mimulus eastwoodiae | Eastwood's monkeyflower | Scrophulariaceae | |
| Mimulus floribundus | manyflowered monkeyflower | Scrophulariaceae | |
| Mimulus glabratus | roundleaf monkeyflower | Scrophulariaceae | |
| Mimulus glabratus var. glabratus | roundleaf monkeyflower | Scrophulariaceae | |
| Mimulus glabratus var. jamesii | James' monkeyflower | Scrophulariaceae | |
| Mimulus guttatus | seep monkeyflower | Scrophulariaceae | |
| Mimulus parryi | annual redspot monkeyflower | Scrophulariaceae | |
| Mimulus primuloides | primrose monkeyflower | Scrophulariaceae | |
| Mimulus primuloides var. primuloides | primrose monkeyflower | Scrophulariaceae | |
| Mimulus rubellus | little redstem monkeyflower | Scrophulariaceae | |
| Mimulus spissus | compact monkeyflower | Scrophulariaceae | |
| Mimulus suksdorfii | Suksdorf's monkeyflower | Scrophulariaceae | |
| Mimulus tilingii | Tiling's monkeyflower | Scrophulariaceae | |
| Mimulus tilingii var. tilingii | Tiling's monkeyflower | Scrophulariaceae | |
| Minuartia | stitchwort | Caryophyllaceae | |
| Minuartia douglasii | Douglas' stitchwort | Caryophyllaceae | |
| Minuartia filiorum | threadbranch stitchwort | Caryophyllaceae | |
| Minuartia obtusiloba | twinflower sandwort | Caryophyllaceae | |
| Minuartia rubella | beautiful sandwort | Caryophyllaceae | |
| Mirabilis | four o'clock | Nyctaginaceae | |
| Mirabilis albida | white four o'clock | Nyctaginaceae | |
| Mirabilis coccinea | scarlet four o'clock | Nyctaginaceae | |
| Mirabilis decipiens | broadleaf four o'clock | Nyctaginaceae | |
| Mirabilis glabra | smooth four o'clock | Nyctaginaceae | |
| Mirabilis hirsuta | hairy four o'clock | Nyctaginaceae | |
| Mirabilis jalapa | marvel of Peru | Nyctaginaceae | |
| Mirabilis laevis | desert wishbone-bush | Nyctaginaceae | |
| Mirabilis laevis var. retrorsa | wishbone-bush | Nyctaginaceae | |
| Mirabilis laevis var. villosa | wishbone-bush | Nyctaginaceae | |
| Mirabilis linearis | narrowleaf four o'clock | Nyctaginaceae | |
| Mirabilis longiflora | sweet four o'clock | Nyctaginaceae | |
| Mirabilis longiflora var. wrightiana | sweet four o'clock | Nyctaginaceae | |
| Mirabilis melanotricha | Nyctaginaceae | ||
| Mirabilis multiflora | Colorado four o'clock | Nyctaginaceae | |
| Mirabilis multiflora var. glandulosa | Colorado four o'clock | Nyctaginaceae | |
| Mirabilis multiflora var. multiflora | Colorado four o'clock | Nyctaginaceae | |
| Mirabilis multiflora var. pubescens | Colorado four o'clock | Nyctaginaceae | |
| Mirabilis oxybaphoides | smooth spreading four o'clock | Nyctaginaceae | |
| Mirabilis pumila | dwarf four o'clock | Nyctaginaceae | |
| Mirabilis tenuiloba | longlobe four o'clock | Nyctaginaceae | |
| Mitracarpus | girdlepod | Rubiaceae | |
| Mitracarpus breviflorus | white girdlepod | Rubiaceae | |
| Modiola | bristlemallow | Malvaceae | |
| Modiola caroliniana | Carolina bristlemallow | Malvaceae | |
| Mohavea | mohavea | Scrophulariaceae | |
| Mohavea breviflora | golden desert-snapdragon | Scrophulariaceae | |
| Mohavea confertiflora | ghost flower | Scrophulariaceae | |
| Mollugo | carpetweed | Molluginaceae | |
| Mollugo cerviana | threadstem carpetweed | Molluginaceae | |
| Mollugo verticillata | green carpetweed | Molluginaceae | |
| Moluccella | moluccella | Lamiaceae | |
| Moluccella laevis | shellflower | Lamiaceae | |
| Monarda | beebalm | Lamiaceae | |
| Monarda citriodora | lemon beebalm | Lamiaceae | |
| Monarda citriodora ssp. austromontana | lemon beebalm | Lamiaceae | |
| Monarda citriodora ssp. citriodora | lemon beebalm | Lamiaceae | |
| Monarda citriodora ssp. citriodora var. citriodora | lemon beebalm | Lamiaceae | |
| Monarda fistulosa | wild bergamot | Lamiaceae | |
| Monarda fistulosa ssp. fistulosa | wild bergamot | Lamiaceae | |
| Monarda fistulosa ssp. fistulosa var. menthifolia | mintleaf bergamot | Lamiaceae | |
| Monarda pectinata | pony beebalm | Lamiaceae | |
| Monardella | monardella | Lamiaceae | |
| Monardella arizonica | Arizona monardella | Lamiaceae | |
| Monardella glauca | pale monardella | Lamiaceae | |
| Monardella lanceolata | mustang monardella | Lamiaceae | |
| Monardella lanceolata var. lanceolata | mustang monardella | Lamiaceae | |
| Monardella linoides | flaxleaf monardella | Lamiaceae | |
| Monardella linoides ssp. linoides | flaxleaf monardella | Lamiaceae | |
| Monardella linoides ssp. stricta | flaxleaf monardella | Lamiaceae | |
| Moneses | single delight | Pyrolaceae | |
| Moneses uniflora | single delight | Pyrolaceae | |
| Monnina | monnina | Polygalaceae | |
| Monnina wrightii | blue pygmyflower | Polygalaceae | |
| Monolepis | povertyweed | Chenopodiaceae | |
| Monolepis nuttalliana | Nuttall's povertyweed | Chenopodiaceae | |
| Monoptilon | desertstar | Asteraceae | |
| Monoptilon bellidiforme | daisy desertstar | Asteraceae | |
| Monoptilon bellioides | Mojave desertstar | Asteraceae | |
| Monotropa | Indianpipe | Monotropaceae | |
| Monotropa hypopithys | pinesap | Monotropaceae | |
| Monroa | false buffalograss | Poaceae | |
| Monroa squarrosa | false buffalograss | Poaceae | |
| Montia | minerslettuce | Portulacaceae | |
| Montia chamissoi | water minerslettuce | Portulacaceae | |
| Mortonia | saddlebush | Celastraceae | |
| Mortonia scabrella | Rio Grande saddlebush | Celastraceae | |
| Mortonia utahensis | Utah mortonia | Celastraceae | |
| Morus | mulberry | Moraceae | |
| Morus alba | white mulberry | Moraceae | |
| Morus microphylla | Texas mulberry | Moraceae | |
| Muhlenbergia | muhly | Poaceae | |
| Muhlenbergia andina | foxtail muhly | Poaceae | |
| Muhlenbergia appressa | Devils Canyon muhly | Poaceae | |
| Muhlenbergia arenacea | ear muhly | Poaceae | |
| Muhlenbergia arenicola | sand muhly | Poaceae | |
| Muhlenbergia arizonica | Arizona muhly | Poaceae | |
| Muhlenbergia asperifolia | scratchgrass | Poaceae | |
| Muhlenbergia brevis | short muhly | Poaceae | |
| Muhlenbergia curtifolia | Utah muhly | Poaceae | |
| Muhlenbergia depauperata | sixweeks muhly | Poaceae | |
| Muhlenbergia dubia | pine muhly | Poaceae | |
| Muhlenbergia dumosa | bamboo muhly | Poaceae | |
| Muhlenbergia elongata | sycamore muhly | Poaceae | |
| Muhlenbergia eludens | gravelbar muhly | Poaceae | |
| Muhlenbergia emersleyi | bullgrass | Poaceae | |
| Muhlenbergia filiculmis | slimstem muhly | Poaceae | |
| Muhlenbergia filiformis | pullup muhly | Poaceae | |
| Muhlenbergia fragilis | delicate muhly | Poaceae | |
| Muhlenbergia glauca | desert muhly | Poaceae | |
| Muhlenbergia longiligula | longtongue muhly | Poaceae | |
| Muhlenbergia mexicana | Mexican muhly | Poaceae | |
| Muhlenbergia microsperma | littleseed muhly | Poaceae | |
| Muhlenbergia minutissima | annual muhly | Poaceae | |
| Muhlenbergia montana | mountain muhly | Poaceae | |
| Muhlenbergia palmeri | southwestern muhly | Poaceae | |
| Muhlenbergia pauciflora | New Mexico muhly | Poaceae | |
| Muhlenbergia pectinata | combtop muhly | Poaceae | |
| Muhlenbergia peruviana | Peruvian muhly | Poaceae | |
| Muhlenbergia polycaulis | cliff muhly | Poaceae | |
| Muhlenbergia porteri | bush muhly | Poaceae | |
| Muhlenbergia pungens | sandhill muhly | Poaceae | |
| Muhlenbergia racemosa | marsh muhly | Poaceae | |
| Muhlenbergia ramulosa | green muhly | Poaceae | |
| Muhlenbergia repens | creeping muhly | Poaceae | |
| Muhlenbergia richardsonis | mat muhly | Poaceae | |
| Muhlenbergia rigens | deergrass | Poaceae | |
| Muhlenbergia rigida | purple muhly | Poaceae | |
| Muhlenbergia schreberi | nimblewill | Poaceae | |
| Muhlenbergia setifolia | curlyleaf muhly | Poaceae | |
| Muhlenbergia sinuosa | marshland muhly | Poaceae | |
| Muhlenbergia straminea | screwleaf muhly | Poaceae | |
| Muhlenbergia sylvatica | woodland muhly | Poaceae | |
| Muhlenbergia tenuifolia | slender muhly | Poaceae | |
| Muhlenbergia texana | Texas muhly | Poaceae | |
| Muhlenbergia thurberi | Thurber's muhly | Poaceae | |
| Muhlenbergia torreyi | ring muhly | Poaceae | |
| Muhlenbergia utilis | aparejograss | Poaceae | |
| Muhlenbergia wrightii | spike muhly | Poaceae | |
| Myosotis | forget-me-not | Boraginaceae | |
| Myosotis scorpioides | true forget-me-not | Boraginaceae | |
| Myosotis verna | spring forget-me-not | Boraginaceae | |
| Myosurus | mousetail | Ranunculaceae | |
| Myosurus apetalus | bristly mousetail | Ranunculaceae | |
| Myosurus apetalus var. montanus | bristly mousetail | Ranunculaceae | |
| Myosurus cupulatus | Arizona mousetail | Ranunculaceae | |
| Myosurus minimus | tiny mousetail | Ranunculaceae | |
| Myosurus nitidus | western mousetail | Ranunculaceae | |
| Myriophyllum | watermilfoil | Haloragaceae | |
| Myriophyllum aquaticum | parrot feather watermilfoil | Haloragaceae | |
| Myriophyllum quitense | Andean watermilfoil | Haloragaceae | |
| Myriophyllum sibiricum | shortspike watermilfoil | Haloragaceae | |
| Myriophyllum spicatum | Eurasian watermilfoil | Haloragaceae | |
| N | |||
| Najas | waternymph | Najadaceae | |
| Najas flexilis | nodding waternymph | Najadaceae | |
| Najas guadalupensis | southern waternymph | Najadaceae | |
| Najas guadalupensis ssp. guadalupensis | southern waternymph | Najadaceae | |
| Najas marina | spiny naiad | Najadaceae | |
| Nama | fiddleleaf | Hydrophyllaceae | |
| Nama demissum | purplemat | Hydrophyllaceae | |
| Nama demissum var. demissum | purplemat | Hydrophyllaceae | |
| Nama dichotomum | wishbone fiddleleaf | Hydrophyllaceae | |
| Nama hispidum | bristly nama | Hydrophyllaceae | |
| Nama pusillum | eggleaf fiddleleaf | Hydrophyllaceae | |
| Nama retrorsum | betatakin fiddleleaf | Hydrophyllaceae | |
| Nama rothrockii | Rothrock's fiddleleaf | Hydrophyllaceae | |
| Nama stenocarpum | mud fiddleleaf | Hydrophyllaceae | |
| Nassella | needlegrass | Poaceae | |
| Nassella viridula | green needlegrass | Poaceae | |
| Nasturtium | Brassicaceae | ||
| Nasturtium officinale | watercress | Brassicaceae | |
| Navarretia | pincushionplant | Polemoniaceae | |
| Navarretia breweri | Brewer's navarretia | Polemoniaceae | |
| Navarretia intertexta | needleleaf navarretia | Polemoniaceae | |
| Navarretia intertexta ssp. propinqua | near navarretia | Polemoniaceae | |
| Navarretia leucocephala | whitehead navarretia | Polemoniaceae | |
| Navarretia leucocephala ssp. minima | least navarretia | Polemoniaceae | |
| Nemacaulis | cottonheads | Polygonaceae | |
| Nemacaulis denudata | cottonheads | Polygonaceae | |
| Nemacaulis denudata var. gracilis | cottonheads | Polygonaceae | |
| Nemacladus | threadplant | Campanulaceae | |
| Nemacladus glanduliferus | glandular threadplant | Campanulaceae | |
| Nemacladus glanduliferus var. glanduliferus | glandular threadplant | Campanulaceae | |
| Nemacladus glanduliferus var. orientalis | glandular threadplant | Campanulaceae | |
| Nemacladus gracilis | slender threadplant | Campanulaceae | |
| Nemacladus longiflorus | longflower threadplant | Campanulaceae | |
| Nemacladus longiflorus var. breviflorus | longflower threadplant | Campanulaceae | |
| Nemacladus longiflorus var. longiflorus | longflower threadplant | Campanulaceae | |
| Nemacladus rubescens | desert threadplant | Campanulaceae | |
| Nemacladus rubescens var. rubescens | desert threadplant | Campanulaceae | |
| Nemacladus sigmoideus | sigmoid threadplant | Campanulaceae | |
| Nemastylis | pleatleaf | Iridaceae | |
| Nemastylis tenuis | southwestern pleatleaf | Iridaceae | |
| Nemastylis tenuis ssp. pringlei | Pringle's pleatleaf | Iridaceae | |
| Neogaerrhinum | neogaerrhinum | Scrophulariaceae | |
| Neogaerrhinum filipes | yellow twining snapdragon | Scrophulariaceae | |
| Nepeta | catnip | Lamiaceae | |
| Nepeta cataria | catnip | Lamiaceae | |
| Nephrolepis | swordfern | Dryopteridaceae | |
| Nephrolepis exaltata | Boston swordfern | Dryopteridaceae | |
| Nephrolepis exaltata ssp. exaltata | Boston swordfern | Dryopteridaceae | |
| Nerium | oleander | Apocynaceae | |
| Nerium oleander | oleander | Apocynaceae | |
| Nicotiana | tobacco | Solanaceae | |
| Nicotiana attenuata | coyote tobacco | Solanaceae | |
| Nicotiana clevelandii | Cleveland's tobacco | Solanaceae | |
| Nicotiana glauca | tree tobacco | Solanaceae | |
| Nicotiana obtusifolia | desert tobacco | Solanaceae | |
| Nicotiana obtusifolia var. obtusifolia | desert tobacco | Solanaceae | |
| Nicotiana obtusifolia var. palmeri | desert tobacco | Solanaceae | |
| Nicotiana quadrivalvis | Indian tobacco | Solanaceae | |
| Nicotiana quadrivalvis var. bigelovii | Bigelow's tobacco | Solanaceae | |
| Nissolia | yellowhood | Fabaceae | |
| Nissolia schottii | Schott's yellowhood | Fabaceae | |
| Nissolia wislizeni | Arizona yellowhood | Fabaceae | |
| Nitrophila | niterwort | Chenopodiaceae | |
| Nitrophila occidentalis | boraxweed | Chenopodiaceae | |
| Noccaea | Brassicaceae | ||
| Noccaea montana | alpine pennycress | Brassicaceae | |
| Noccaea montana var. fendleri | Fendler's pennycress | Brassicaceae | |
| Noccaea montana var. montana | alpine pennycress | Brassicaceae | |
| Nolina | beargrass | Liliaceae | |
| Nolina bigelovii | Bigelow's nolina | Liliaceae | |
| Nolina microcarpa | sacahuista | Liliaceae | |
| Nolina parryi | Parry's beargrass | Liliaceae | |
| Nolina texana | Texas sacahuista | Liliaceae | |
| Notholaena | cloak fern | Pteridaceae | |
| Notholaena aschenborniana | scaled cloak fern | Pteridaceae | |
| Notholaena californica | California cloak fern | Pteridaceae | |
| Notholaena californica ssp. californica | California cloak fern | Pteridaceae | |
| Notholaena grayi | Gray's cloak fern | Pteridaceae | |
| Notholaena grayi ssp. grayi | Gray's cloak fern | Pteridaceae | |
| Notholaena grayi ssp. sonorensis | Sonoran cloak fern | Pteridaceae | |
| Notholaena lemmonii | Lemmon's cloak fern | Pteridaceae | |
| Notholaena neglecta | Maxon's cloak fern | Pteridaceae | |
| Notholaena standleyi | star cloak fern | Pteridaceae | |
| Nothoscordum | false garlic | Liliaceae | |
| Nothoscordum texanum | Texas false garlic | Liliaceae | |
| Nuphar | pond-lily | Nymphaeaceae | |
| Nuphar lutea | yellow pond-lily | Nymphaeaceae | |
| Nuphar lutea ssp. polysepala | Rocky Mountain pond-lily | Nymphaeaceae | |
| Nuttallanthus | toadflax | Scrophulariaceae | |
| Nuttallanthus texanus | Texas toadflax | Scrophulariaceae | |
| Nymphaea | waterlily | Nymphaeaceae | |
| Nymphaea mexicana | yellow waterlily | Nymphaeaceae | |
| Nymphaea odorata | American white waterlily | Nymphaeaceae | |
| Nymphaea odorata ssp. odorata | American white waterlily | Nymphaeaceae | |
| Nymphoides | floatingheart | Menyanthaceae | |
| Nymphoides peltata | yellow floatingheart | Menyanthaceae | |
| O | |||
| Ocimum | basil | Lamiaceae | |
| Ocimum basilicum | sweet basil | Lamiaceae | |
| Oenothera | evening primrose | Onagraceae | |
| Oenothera albicaulis | whitest evening primrose | Onagraceae | |
| Oenothera arizonica | California evening primrose | Onagraceae | |
| Oenothera brachycarpa | shortfruit evening primrose | Onagraceae | |
| Oenothera caespitosa | tufted evening primrose | Onagraceae | |
| Oenothera caespitosa ssp. crinita | tufted evening primrose | Onagraceae | |
| Oenothera caespitosa ssp. marginata | tufted evening primrose | Onagraceae | |
| Oenothera caespitosa ssp. navajoensis | Navajo evening primrose | Onagraceae | |
| Oenothera californica | California evening primrose | Onagraceae | |
| Oenothera californica ssp. avita | California evening primrose | Onagraceae | |
| Oenothera cavernae | cavedwelling evening primrose | Onagraceae | |
| Oenothera coronopifolia | crownleaf evening primrose | Onagraceae | |
| Oenothera deltoides | birdcage evening primrose | Onagraceae | |
| Oenothera deltoides ssp. ambigua | birdcage evening primrose | Onagraceae | |
| Oenothera deltoides ssp. deltoides | birdcage evening primrose | Onagraceae | |
| Oenothera elata | Hooker's evening primrose | Onagraceae | |
| Oenothera elata ssp. hirsutissima | Hooker's evening primrose | Onagraceae | |
| Oenothera flava | yellow evening primrose | Onagraceae | |
| Oenothera flava ssp. flava | yellow evening primrose | Onagraceae | |
| Oenothera flava ssp. taraxacoides | yellow evening primrose | Onagraceae | |
| Oenothera havardii | Havard's evening primrose | Onagraceae | |
| Oenothera kunthiana | Kunth's evening primrose | Onagraceae | |
| Oenothera longissima | longstem evening primrose | Onagraceae | |
| Oenothera neomexicana | New Mexico evening primrose | Onagraceae | |
| Oenothera pallida | pale evening primrose | Onagraceae | |
| Oenothera pallida ssp. pallida | pale evening primrose | Onagraceae | |
| Oenothera pallida ssp. runcinata | pale evening primrose | Onagraceae | |
| Oenothera pallida ssp. trichocalyx | pale evening primrose | Onagraceae | |
| Oenothera platanorum | Fort Huachuca evening primrose | Onagraceae | |
| Oenothera primiveris | desert evening primrose | Onagraceae | |
| Oenothera primiveris ssp. bufonis | desert evening primrose | Onagraceae | |
| Oenothera primiveris ssp. primiveris | desert evening primrose | Onagraceae | |
| Oenothera pubescens | South American evening primrose | Onagraceae | |
| Oenothera rosea | rose evening primrose | Onagraceae | |
| Oenothera speciosa | pinkladies | Onagraceae | |
| Oenothera villosa | hairy evening primrose | Onagraceae | |
| Oenothera villosa ssp. strigosa | hairy evening primrose | Onagraceae | |
| Oligomeris | oligomeris | Resedaceae | |
| Oligomeris linifolia | lineleaf whitepuff | Resedaceae | |
| Olneya | olneya | Fabaceae | |
| Olneya tesota | desert ironwood | Fabaceae | |
| Onopordum | cottonthistle | Asteraceae | |
| Onopordum acanthium | Scotch cottonthistle | Asteraceae | |
| Ophioglossum | adderstongue | Ophioglossaceae | |
| Ophioglossum engelmannii | limestone adderstongue | Ophioglossaceae | |
| Ophioglossum polyphyllum | large adderstongue | Ophioglossaceae | |
| Ophioglossum vulgatum | southern adderstongue | Ophioglossaceae | |
| Opuntia | pricklypear | Cactaceae | |
| Opuntia aurea | golden pricklypear | Cactaceae | |
| Opuntia basilaris | beavertail pricklypear | Cactaceae | |
| Opuntia basilaris var. basilaris | beavertail pricklypear | Cactaceae | |
| Opuntia basilaris var. longiareolata | beavertail pricklypear | Cactaceae | |
| Opuntia chlorotica | dollarjoint pricklypear | Cactaceae | |
| Opuntia curvospina | searchlight pricklypear | Cactaceae | |
| Opuntia engelmannii | cactus apple | Cactaceae | |
| Opuntia engelmannii var. engelmannii | cactus apple | Cactaceae | |
| Opuntia engelmannii var. flavispina | cactus apple | Cactaceae | |
| Opuntia ficus-indica | Barbary fig | Cactaceae | |
| Opuntia fragilis | brittle pricklypear | Cactaceae | |
| Opuntia gosseliniana | violet pricklypear | Cactaceae | |
| Opuntia laevis | tulip pricklypear | Cactaceae | |
| Opuntia macrocentra | purple pricklypear | Cactaceae | |
| Opuntia macrocentra var. macrocentra | purple pricklypear | Cactaceae | |
| Opuntia macrorhiza | twistspine pricklypear | Cactaceae | |
| Opuntia macrorhiza var. macrorhiza | twistspine pricklypear | Cactaceae | |
| Opuntia macrorhiza var. pottsii | twistspine pricklypear | Cactaceae | |
| Opuntia martiniana | seashore cactus | Cactaceae | |
| Opuntia microdasys | angel's-wings | Cactaceae | |
| Opuntia phaeacantha | tulip pricklypear | Cactaceae | |
| Opuntia pinkavae | Pinkava's pricklypear | Cactaceae | |
| Opuntia polyacantha | plains pricklypear | Cactaceae | |
| Opuntia polyacantha var. erinacea | grizzlybear pricklypear | Cactaceae | |
| Opuntia polyacantha var. hystricina | grizzlybear pricklypear | Cactaceae | |
| Opuntia polyacantha var. nicholii | Navajo Bridge pricklypear | Cactaceae | |
| Opuntia polyacantha var. polyacantha | hairspine pricklypear | Cactaceae | |
| Opuntia santa-rita | Santa Rita pricklypear | Cactaceae | |
| Opuntia vaseyi | Vasey's coastal pricklypear | Cactaceae | |
| Oreochrysum | goldenrod | Asteraceae | |
| Oreochrysum parryi | Parry's goldenrod | Asteraceae | |
| Oreoxis | oreoxis | Apiaceae | |
| Oreoxis alpina | alpine oreoxis | Apiaceae | |
| Oreoxis alpina ssp. alpina | alpine oreoxis | Apiaceae | |
| Orobanche | broomrape | Orobanchaceae | |
| Orobanche cooperi | desert broomrape | Orobanchaceae | |
| Orobanche cooperi ssp. cooperi | desert broomrape | Orobanchaceae | |
| Orobanche cooperi ssp. latiloba | desert broomrape | Orobanchaceae | |
| Orobanche fasciculata | clustered broomrape | Orobanchaceae | |
| Orobanche ludoviciana | Louisiana broomrape | Orobanchaceae | |
| Orobanche ludoviciana ssp. ludoviciana | Louisiana broomrape | Orobanchaceae | |
| Orobanche ludoviciana ssp. multiflora | manyflower broomrape | Orobanchaceae | |
| Orobanche multicaulis | spiked broomrape | Orobanchaceae | |
| Orobanche uniflora | oneflowered broomrape | Orobanchaceae | |
| Orthilia | orthilia | Pyrolaceae | |
| Orthilia secunda | sidebells wintergreen | Pyrolaceae | |
| Orthocarpus | owl's-clover | Scrophulariaceae | |
| Orthocarpus luteus | yellow owl's-clover | Scrophulariaceae | |
| Orthocarpus purpureoalbus | purplewhite owl's-clover | Scrophulariaceae | |
| Osmorhiza | sweetroot | Apiaceae | |
| Osmorhiza berteroi | sweetcicely | Apiaceae | |
| Osmorhiza brachypoda | California sweetcicely | Apiaceae | |
| Osmorhiza depauperata | bluntseed sweetroot | Apiaceae | |
| Ostrya | hophornbeam | Betulaceae | |
| Ostrya knowltonii | Knowlton's hophornbeam | Betulaceae | |
| Oxalis | woodsorrel | Oxalidaceae | |
| Oxalis albicans | radishroot woodsorrel | Oxalidaceae | |
| Oxalis albicans ssp. albicans | radishroot woodsorrel | Oxalidaceae | |
| Oxalis albicans ssp. pilosa | radishroot woodsorrel | Oxalidaceae | |
| Oxalis alpina | alpine woodsorrel | Oxalidaceae | |
| Oxalis caerulea | blue woodsorrel | Oxalidaceae | |
| Oxalis corniculata | creeping woodsorrel | Oxalidaceae | |
| Oxalis decaphylla | tenleaf woodsorrel | Oxalidaceae | |
| Oxalis dillenii | slender yellow woodsorrel | Oxalidaceae | |
| Oxalis drummondii | Drummond's woodsorrel | Oxalidaceae | |
| Oxalis latifolia | broadleaf woodsorrel | Oxalidaceae | |
| Oxalis pes-caprae | Bermuda buttercup | Oxalidaceae | |
| Oxalis stricta | common yellow oxalis | Oxalidaceae | |
| Oxalis violacea | violet woodsorrel | Oxalidaceae | |
| Oxypolis | cowbane | Apiaceae | |
| Oxypolis fendleri | Fendler's cowbane | Apiaceae | |
| Oxyria | mountainsorrel | Polygonaceae | |
| Oxyria digyna | alpine mountainsorrel | Polygonaceae | |
| Oxytenia | Asteraceae | ||
| Oxytenia acerosa | copperweed | Asteraceae | |
| Oxytheca | oxytheca | Polygonaceae | |
| Oxytheca perfoliata | roundleaf oxytheca | Polygonaceae | |
| Oxytropis | locoweed | Fabaceae | |
| Oxytropis lambertii | purple locoweed | Fabaceae | |
| Oxytropis lambertii var. bigelovii | purple locoweed | Fabaceae | |
| Oxytropis oreophila | mountain oxytrope | Fabaceae | |
| Oxytropis oreophila var. juniperina | mountain oxytrope | Fabaceae | |
| Oxytropis oreophila var. oreophila | mountain oxytrope | Fabaceae | |
| P | |||
| Pachycereus | pachycereus | Cactaceae | |
| Pachycereus schottii | senita cactus | Cactaceae | |
| Packera | ragwort | Asteraceae | |
| Packera cardamine | bittercress ragwort | Asteraceae | |
| Packera cynthioides | White Mountain ragwort | Asteraceae | |
| Packera franciscana | San Francisco Peaks ragwort | Asteraceae | |
| Packera hartiana | Hart's ragwort | Asteraceae | |
| Packera multilobata | lobeleaf groundsel | Asteraceae | |
| Packera neomexicana | New Mexico groundsel | Asteraceae | |
| Packera neomexicana var. metcalfei | Metcalf's groundsel | Asteraceae | |
| Packera neomexicana var. mutabilis | New Mexico groundsel | Asteraceae | |
| Packera neomexicana var. neomexicana | New Mexico groundsel | Asteraceae | |
| Packera neomexicana var. toumeyi | Toumey's groundsel | Asteraceae | |
| Packera plattensis | prairie groundsel | Asteraceae | |
| Packera quaerens | Mogollon Mountain ragwort | Asteraceae | |
| Packera quercetorum | Oak Creek ragwort | Asteraceae | |
| Packera werneriifolia | hoary groundsel | Asteraceae | |
| Palafoxia | palafox | Asteraceae | |
| Palafoxia arida | desert palafox | Asteraceae | |
| Palafoxia arida var. arida | desert palafox | Asteraceae | |
| Palafoxia arida var. gigantea | giant Spanish needle | Asteraceae | |
| Panicum | panicgrass | Poaceae | |
| Panicum alatum | winged panicgrass | Poaceae | |
| Panicum alatum var. alatum | winged panicgrass | Poaceae | |
| Panicum alatum var. minus | winged panicgrass | Poaceae | |
| Panicum antidotale | blue panicum | Poaceae | |
| Panicum bulbosum | bulb panicgrass | Poaceae | |
| Panicum capillare | witchgrass | Poaceae | |
| Panicum dichotomiflorum | fall panicgrass | Poaceae | |
| Panicum dichotomiflorum var. dichotomiflorum | fall panicgrass | Poaceae | |
| Panicum hallii | Hall's panicgrass | Poaceae | |
| Panicum hallii var. hallii | Hall's panicgrass | Poaceae | |
| Panicum hirticaule | Mexican panicgrass | Poaceae | |
| Panicum hirticaule var. hirticaule | Mexican panicgrass | Poaceae | |
| Panicum hirticaule var. stramineum | Sonoran panicgrass | Poaceae | |
| Panicum hirticaule var. verrucosum | Mexican panicgrass | Poaceae | |
| Panicum miliaceum | broomcorn millet | Poaceae | |
| Panicum miliaceum ssp. miliaceum | broomcorn millet | Poaceae | |
| Panicum mohavense | Mojave panicgrass | Poaceae | |
| Panicum obtusum | vine mesquite | Poaceae | |
| Panicum urvilleanum | desert panicgrass | Poaceae | |
| Panicum virgatum | switchgrass | Poaceae | |
| Panicum virgatum var. virgatum | switchgrass | Poaceae | |
| Papaver | poppy | Papaveraceae | |
| Papaver somniferum | opium poppy | Papaveraceae | |
| Pappophorum | pappusgrass | Poaceae | |
| Pappophorum vaginatum | whiplash pappusgrass | Poaceae | |
| Paraserianthes | paraserianthes | Fabaceae | |
| Paraserianthes lophantha | plume albizia | Fabaceae | |
| Parietaria | pellitory | Urticaceae | |
| Parietaria hespera | rillita pellitory | Urticaceae | |
| Parietaria hespera var. hespera | rillita pellitory | Urticaceae | |
| Parietaria pensylvanica | Pennsylvania pellitory | Urticaceae | |
| Parkinsonia | paloverde | Fabaceae | |
| Parkinsonia aculeata | Jerusalem thorn | Fabaceae | |
| Parkinsonia florida | blue paloverde | Fabaceae | |
| Parkinsonia microphylla | yellow paloverde | Fabaceae | |
| Parnassia | grass of Parnassus | Saxifragaceae | |
| Parnassia palustris | marsh grass of Parnassus | Saxifragaceae | |
| Parnassia palustris var. montanensis | mountain grass of Parnassus | Saxifragaceae | |
| Paronychia | nailwort | Caryophyllaceae | |
| Paronychia jamesii | James' nailwort | Caryophyllaceae | |
| Paronychia sessiliflora | creeping nailwort | Caryophyllaceae | |
| Parryella | parryella | Fabaceae | |
| Parryella filifolia | common dunebroom | Fabaceae | |
| Parthenice | parthenice | Asteraceae | |
| Parthenice mollis | annual monsterwort | Asteraceae | |
| Parthenium | feverfew | Asteraceae | |
| Parthenium confertum | Gray's feverfew | Asteraceae | |
| Parthenium confertum var. lyratum | Gray's feverfew | Asteraceae | |
| Parthenium incanum | mariola | Asteraceae | |
| Parthenocissus | creeper | Vitaceae | |
| Parthenocissus vitacea | woodbine | Vitaceae | |
| Pascopyrum | wheatgrass | Poaceae | |
| Pascopyrum smithii | western wheatgrass | Poaceae | |
| Paspalum | crowngrass | Poaceae | |
| Paspalum dilatatum | dallisgrass | Poaceae | |
| Paspalum distichum | knotgrass | Poaceae | |
| Paspalum setaceum | thin paspalum | Poaceae | |
| Paspalum virletii | Virlet's paspalum | Poaceae | |
| Passiflora | passionflower | Passifloraceae | |
| Passiflora bryonioides | cupped passionflower | Passifloraceae | |
| Passiflora foetida | fetid passionflower | Passifloraceae | |
| Passiflora foetida var. arizonica | Arizonia passionflower | Passifloraceae | |
| Passiflora mexicana | Mexican passionflower | Passifloraceae | |
| Pastinaca | parsnip | Apiaceae | |
| Pastinaca sativa | wild parsnip | Apiaceae | |
| Paxistima | paxistima | Celastraceae | |
| Paxistima myrsinites | Oregon boxleaf | Celastraceae | |
| Pectis | chinchweed | Asteraceae | |
| Pectis angustifolia | lemonscent | Asteraceae | |
| Pectis angustifolia var. angustifolia | narrowleaf pectis | Asteraceae | |
| Pectis cylindrica | Sonoran chinchweed | Asteraceae | |
| Pectis filipes | fivebract chinchweed | Asteraceae | |
| Pectis filipes var. subnuda | fivebract chinchweed | Asteraceae | |
| Pectis imberbis | beardless chinchweed | Asteraceae | |
| Pectis linifolia | romero macho | Asteraceae | |
| Pectis longipes | longstalk chinchweed | Asteraceae | |
| Pectis papposa | manybristle chinchweed | Asteraceae | |
| Pectis papposa var. grandis | manybristle chinchweed | Asteraceae | |
| Pectis papposa var. papposa | manybristle chinchweed | Asteraceae | |
| Pectis prostrata | spreading chinchweed | Asteraceae | |
| Pectis rusbyi | Rusby's chinchweed | Asteraceae | |
| Pectocarya | combseed | Boraginaceae | |
| Pectocarya heterocarpa | chuckwalla combseed | Boraginaceae | |
| Pectocarya penicillata | sleeping combseed | Boraginaceae | |
| Pectocarya platycarpa | broadfruit combseed | Boraginaceae | |
| Pectocarya recurvata | curvenut combseed | Boraginaceae | |
| Pectocarya setosa | moth combseed | Boraginaceae | |
| Pedicularis | lousewort | Scrophulariaceae | |
| Pedicularis centranthera | dwarf lousewort | Scrophulariaceae | |
| Pedicularis groenlandica | elephanthead lousewort | Scrophulariaceae | |
| Pedicularis parryi | Parry's lousewort | Scrophulariaceae | |
| Pedicularis parryi ssp. mogollonica | Mogollon lousewort | Scrophulariaceae | |
| Pedicularis parryi ssp. parryi | Parry's lousewort | Scrophulariaceae | |
| Pedicularis procera | giant lousewort | Scrophulariaceae | |
| Pedicularis racemosa | sickletop lousewort | Scrophulariaceae | |
| Pedicularis racemosa ssp. alba | sickletop lousewort | Scrophulariaceae | |
| Pediocactus | pincushion cactus | Cactaceae | |
| Pediocactus bradyi | Brady's pincushion cactus | Cactaceae | |
| Pediocactus paradinei | Kaibab pincushion cactus | Cactaceae | |
| Pediocactus peeblesianus | Navajo pincushion cactus | Cactaceae | |
| Pediocactus simpsonii | mountain ball cactus | Cactaceae | |
| Pediocactus simpsonii var. simpsonii | mountain ball cactus | Cactaceae | |
| Pediomelum | Indian breadroot | Fabaceae | |
| Pediomelum aromaticum | aromatic Indian breadroot | Fabaceae | |
| Pediomelum castoreum | beaver Indian breadroot | Fabaceae | |
| Pediomelum megalanthum | Intermountain Indian breadroot | Fabaceae | |
| Pediomelum megalanthum var. epipsilum | Intermountain Indian breadroot | Fabaceae | |
| Pediomelum megalanthum var. megalanthum | Intermountain Indian breadroot | Fabaceae | |
| Pediomelum megalanthum var. retrorsum | Intermountain Indian breadroot | Fabaceae | |
| Pediomelum mephiticum | skunktop | Fabaceae | |
| Pediomelum pentaphyllum | small Indian breadroot | Fabaceae | |
| Peganum | peganum | Zygophyllaceae | |
| Peganum harmala | harmal peganum | Zygophyllaceae | |
| Pellaea | cliffbrake | Pteridaceae | |
| Pellaea atropurpurea | purple cliffbrake | Pteridaceae | |
| Pellaea glabella | smooth cliffbrake | Pteridaceae | |
| Pellaea glabella ssp. simplex | smooth cliffbrake | Pteridaceae | |
| Pellaea intermedia | intermediate cliffbrake | Pteridaceae | |
| Pellaea lyngholmii | Lyngholm's cliffbrake | Pteridaceae | |
| Pellaea mucronata | birdfoot cliffbrake | Pteridaceae | |
| Pellaea mucronata ssp. mucronata | birdfoot cliffbrake | Pteridaceae | |
| Pellaea ternifolia | Trans-Pecos cliffbrake | Pteridaceae | |
| Pellaea ternifolia ssp. arizonica | Arizonia cliffbrake | Pteridaceae | |
| Pellaea truncata | spiny cliffbrake | Pteridaceae | |
| Pellaea wrightiana | Wright's cliffbrake | Pteridaceae | |
| Peniocereus | peniocereus | Cactaceae | |
| Peniocereus greggii | nightblooming cereus | Cactaceae | |
| Peniocereus greggii var. greggii | nightblooming cereus | Cactaceae | |
| Peniocereus greggii var. transmontanus | nightblooming cereus | Cactaceae | |
| Peniocereus striatus | gearstem cactus | Cactaceae | |
| Pennellia | mock thelypody | Brassicaceae | |
| Pennellia longifolia | longleaf mock thelypody | Brassicaceae | |
| Pennellia micrantha | mountain mock thelypody | Brassicaceae | |
| Pennisetum | fountaingrass | Poaceae | |
| Pennisetum ciliare | buffelgrass | Poaceae | |
| Pennisetum glaucum | pearl millet | Poaceae | |
| Pennisetum setaceum | crimson fountaingrass | Poaceae | |
| Penstemon | beardtongue | Scrophulariaceae | |
| Penstemon albomarginatus | whitemargin beardtongue | Scrophulariaceae | |
| Penstemon ambiguus | gilia beardtongue | Scrophulariaceae | |
| Penstemon ambiguus var. laevissimus | pink plains beardtongue | Scrophulariaceae | |
| Penstemon angustifolius | broadbeard beardtongue | Scrophulariaceae | |
| Penstemon angustifolius var. venosus | broadbeard beardtongue | Scrophulariaceae | |
| Penstemon barbatus | beardlip penstemon | Scrophulariaceae | |
| Penstemon barbatus ssp. barbatus | beardlip penstemon | Scrophulariaceae | |
| Penstemon barbatus ssp. torreyi | Torrey's penstemon | Scrophulariaceae | |
| Penstemon barbatus ssp. trichander | beardlip penstemon | Scrophulariaceae | |
| Penstemon bicolor | pinto beardtongue | Scrophulariaceae | |
| Penstemon bicolor ssp. roseus | pinto beardtongue | Scrophulariaceae | |
| Penstemon breviculus | shortstem beardtongue | Scrophulariaceae | |
| Penstemon caespitosus | mat penstemon | Scrophulariaceae | |
| Penstemon caespitosus var. desertipicti | mat penstemon | Scrophulariaceae | |
| Penstemon clutei | Sunset Crater beardtongue | Scrophulariaceae | |
| Penstemon cobaea | cobaea beardtongue | Scrophulariaceae | |
| Penstemon comarrhenus | dusty beardtongue | Scrophulariaceae | |
| Penstemon crideri | Scrophulariaceae | ||
| Penstemon dasyphyllus | Cochise beardtongue | Scrophulariaceae | |
| Penstemon deaveri | Mt. Graham beardtongue | Scrophulariaceae | |
| Penstemon discolor | Cataiina beardtongue | Scrophulariaceae | |
| Penstemon distans | Mt. Tumbull beardtongue | Scrophulariaceae | |
| Penstemon eatonii | firecracker penstemon | Scrophulariaceae | |
| Penstemon eatonii ssp. eatonii | firecracker penstemon | Scrophulariaceae | |
| Penstemon eatonii ssp. exsertus | firecracker penstemon | Scrophulariaceae | |
| Penstemon eatonii ssp. undosus | firecracker penstemon | Scrophulariaceae | |
| Penstemon fendleri | Fendler's penstemon | Scrophulariaceae | |
| Penstemon laevis | southwestern beardtongue | Scrophulariaceae | |
| Penstemon lentus | handsome beardtongue | Scrophulariaceae | |
| Penstemon lentus var. lentus | handsome beardtongue | Scrophulariaceae | |
| Penstemon linarioides | toadflax penstemon | Scrophulariaceae | |
| Penstemon linarioides ssp. coloradoensis | toadflax penstemon | Scrophulariaceae | |
| Penstemon linarioides ssp. compactifolius | toadflax beardtongue | Scrophulariaceae | |
| Penstemon linarioides ssp. linarioides | toadflax beardtongue | Scrophulariaceae | |
| Penstemon linarioides ssp. maguirei | Maguire's penstemon | Scrophulariaceae | |
| Penstemon linarioides ssp. sileri | Siler's penstemon | Scrophulariaceae | |
| Penstemon mirus | Scrophulariaceae | ||
| Penstemon nudiflorus | Flagstaff beardtongue | Scrophulariaceae | |
| Penstemon oliganthus | Apache beardtongue | Scrophulariaceae | |
| Penstemon ophianthus | coiled anther penstemon | Scrophulariaceae | |
| Penstemon pachyphyllus | thickleaf beardtongue | Scrophulariaceae | |
| Penstemon pachyphyllus var. congestus | thickleaf beardtongue | Scrophulariaceae | |
| Penstemon palmeri | Palmer's penstemon | Scrophulariaceae | |
| Penstemon palmeri var. eglandulosus | scented beardtongue | Scrophulariaceae | |
| Penstemon palmeri var. palmeri | Palmer's penstemon | Scrophulariaceae | |
| Penstemon parryi | Parry's beardtongue | Scrophulariaceae | |
| Penstemon petiolatus | petiolate beardtongue | Scrophulariaceae | |
| Penstemon pinifolius | pineneedle beardtongue | Scrophulariaceae | |
| Penstemon pseudoputus | Kaibab Plateau beardtongue | Scrophulariaceae | |
| Penstemon pseudospectabilis | desert penstemon | Scrophulariaceae | |
| Penstemon pseudospectabilis ssp. connatifolius | desert beardtongue | Scrophulariaceae | |
| Penstemon pseudospectabilis ssp. pseudospectabilis | desert beardtongue | Scrophulariaceae | |
| Penstemon putus | Black River beardtongue | Scrophulariaceae | |
| Penstemon ramosus | lanceleaf beardtongue | Scrophulariaceae | |
| Penstemon rostriflorus | Bridge penstemon | Scrophulariaceae | |
| Penstemon rydbergii | Rydberg's penstemon | Scrophulariaceae | |
| Penstemon rydbergii var. aggregatus | meadow beardtongue | Scrophulariaceae | |
| Penstemon rydbergii var. rydbergii | swollen penstemon | Scrophulariaceae | |
| Penstemon stenophyllus | Sonoran beardtongue | Scrophulariaceae | |
| Penstemon strictiformis | Mancos penstemon | Scrophulariaceae | |
| Penstemon strictus | Rocky Mountain penstemon | Scrophulariaceae | |
| Penstemon subulatus | hackberry beardtongue | Scrophulariaceae | |
| Penstemon superbus | superb beardtongue | Scrophulariaceae | |
| Penstemon thompsoniae | Thompson's beardtongue | Scrophulariaceae | |
| Penstemon thompsoniae ssp. thompsoniae | Thompson's beardtongue | Scrophulariaceae | |
| Penstemon thurberi | Thurber's penstemon | Scrophulariaceae | |
| Penstemon utahensis | Utah penstemon | Scrophulariaceae | |
| Penstemon virgatus | upright blue beardtongue | Scrophulariaceae | |
| Penstemon watsonii | Watson's penstemon | Scrophulariaceae | |
| Penstemon whippleanus | Whipple's penstemon | Scrophulariaceae | |
| Pentagramma | goldback fern | Pteridaceae | |
| Pentagramma triangularis | goldback fern | Pteridaceae | |
| Pentagramma triangularis ssp. maxonii | Maxon's goldback fern | Pteridaceae | |
| Pentzia | pentzia | Asteraceae | |
| Pentzia incana | African sheepbush | Asteraceae | |
| Pericome | pericome | Asteraceae | |
| Pericome caudata | mountain tail-leaf | Asteraceae | |
| Perideridia | yampah | Apiaceae | |
| Perideridia parishii | Parish's yampah | Apiaceae | |
| Perideridia parishii ssp. parishii | Parish's yampah | Apiaceae | |
| Perityle | rockdaisy | Asteraceae | |
| Perityle ajoensis | Ajo rockdaisy | Asteraceae | |
| Perityle ambrosiifolia | lace-leaved rockdaisy | Asteraceae | |
| Perityle ciliata | fringed rockdaisy | Asteraceae | |
| Perityle cochisensis | Cochise rockdaisy | Asteraceae | |
| Perityle congesta | Grand Canyon rockdaisy | Asteraceae | |
| Perityle coronopifolia | crowfoot rockdaisy | Asteraceae | |
| Perityle emoryi | Emory's rockdaisy | Asteraceae | |
| Perityle gilensis | Gila rockdaisy | Asteraceae | |
| Perityle gilensis var. gilensis | Gila rockdaisy | Asteraceae | |
| Perityle gilensis var. salensis | Salt River rockdaisy | Asteraceae | |
| Perityle gracilis | three-lobed rockdaisy | Asteraceae | |
| Perityle lemmonii | Lemmon's rockdaisy | Asteraceae | |
| Perityle microglossa | shortray rockdaisy | Asteraceae | |
| Perityle saxicola | Roosevelt Dam rockdaisy | Asteraceae | |
| Perityle tenella | Springdale rockdaisy | Asteraceae | |
| Petalonyx | sandpaper plant | Loasaceae | |
| Petalonyx linearis | narrowleaf sandpaper plant | Loasaceae | |
| Petalonyx nitidus | shinyleaf sandpaper plant | Loasaceae | |
| Petalonyx parryi | Parry's sandpaper plant | Loasaceae | |
| Petalonyx thurberi | Thurber's sandpaper plant | Loasaceae | |
| Petalonyx thurberi ssp. thurberi | Thurber's sandpaper plant | Loasaceae | |
| Peteria | peteria | Fabaceae | |
| Peteria scoparia | rush peteria | Fabaceae | |
| Peteria thompsoniae | Thompson's peteria | Fabaceae | |
| Petradoria | rock goldenrod | Asteraceae | |
| Petradoria pumila | rock goldenrod | Asteraceae | |
| Petradoria pumila ssp. graminea | grass-leaved rock goldenrod | Asteraceae | |
| Petradoria pumila ssp. pumila | rock goldenrod | Asteraceae | |
| Petrophytum | rockspirea | Rosaceae | |
| Petrophytum caespitosum | mat rockspirea | Rosaceae | |
| Petrophytum caespitosum var. caespitosum | mat rockspirea | Rosaceae | |
| Petrophytum caespitosum var. elatius | mat rockspirea | Rosaceae | |
| Peucephyllum | pygmycedar | Asteraceae | |
| Peucephyllum schottii | Schott's pygmycedar | Asteraceae | |
| Phacelia | phacelia | Hydrophyllaceae | |
| Phacelia affinis | limestone phacelia | Hydrophyllaceae | |
| Phacelia alba | white phacelia | Hydrophyllaceae | |
| Phacelia arizonica | Arizona phacelia | Hydrophyllaceae | |
| Phacelia bombycina | Mangas Spring phacelia | Hydrophyllaceae | |
| Phacelia campanularia | desertbells | Hydrophyllaceae | |
| Phacelia campanularia ssp. campanularia | desertbells | Hydrophyllaceae | |
| Phacelia cephalotes | virgin phacelia | Hydrophyllaceae | |
| Phacelia coerulea | skyblue phacelia | Hydrophyllaceae | |
| Phacelia constancei | Constance's phacelia | Hydrophyllaceae | |
| Phacelia crenulata | cleftleaf wildheliotrope | Hydrophyllaceae | |
| Phacelia crenulata var. ambigua | purplestem phacelia | Hydrophyllaceae | |
| Phacelia crenulata var. angustifolia | cleftleaf phacelia | Hydrophyllaceae | |
| Phacelia crenulata var. corrugata | cleftleaf wildheiotrope | Hydrophyllaceae | |
| Phacelia crenulata var. crenulata | cleftleaf wildheliotrope | Hydrophyllaceae | |
| Phacelia crenulata var. minutiflora | cleftleaf wildheliotrope | Hydrophyllaceae | |
| Phacelia cronquistiana | Cronquist's phacelia | Hydrophyllaceae | |
| Phacelia cryptantha | hiddenflower phacelia | Hydrophyllaceae | |
| Phacelia curvipes | Washoe phacelia | Hydrophyllaceae | |
| Phacelia demissa | Intermountain phacelia | Hydrophyllaceae | |
| Phacelia demissa var. demissa | Intermountain phacelia | Hydrophyllaceae | |
| Phacelia distans | distant phacelia | Hydrophyllaceae | |
| Phacelia egena | Kaweah River phacelia | Hydrophyllaceae | |
| Phacelia filiformis | narrow phacelia | Hydrophyllaceae | |
| Phacelia fremontii | Fremont's phacelia | Hydrophyllaceae | |
| Phacelia glechomifolia | pennyroyal leaf phacelia | Hydrophyllaceae | |
| Phacelia heterophylla | varileaf phacelia | Hydrophyllaceae | |
| Phacelia heterophylla ssp. heterophylla | varileaf phacelia | Hydrophyllaceae | |
| Phacelia howelliana | harlequin phacelia | Hydrophyllaceae | |
| Phacelia integrifolia | gypsum phacelia | Hydrophyllaceae | |
| Phacelia integrifolia var. integrifolia | gypsum phacelia | Hydrophyllaceae | |
| Phacelia ivesiana | Ives' phacelia | Hydrophyllaceae | |
| Phacelia ivesiana var. ivesiana | Ives' phacelia | Hydrophyllaceae | |
| Phacelia ivesiana var. pediculoides | Ives' phacelia | Hydrophyllaceae | |
| Phacelia laxiflora | dozing phacelia | Hydrophyllaceae | |
| Phacelia lemmonii | Lemmon's phacelia | Hydrophyllaceae | |
| Phacelia neglecta | alkali phacelia | Hydrophyllaceae | |
| Phacelia neomexicana | New Mexico phacelia | Hydrophyllaceae | |
| Phacelia palmeri | Palmer's phacelia | Hydrophyllaceae | |
| Phacelia parishii | Parish's phacelia | Hydrophyllaceae | |
| Phacelia parryi | Parry's phacelia | Hydrophyllaceae | |
| Phacelia pedicellata | pedicellate phacelia | Hydrophyllaceae | |
| Phacelia pulchella | beautiful phacelia | Hydrophyllaceae | |
| Phacelia pulchella var. gooddingii | Goodding's phacelia | Hydrophyllaceae | |
| Phacelia pulchella var. pulchella | beautiful phacelia | Hydrophyllaceae | |
| Phacelia rafaelensis | plateau phacelia | Hydrophyllaceae | |
| Phacelia ramosissima | branching phacelia | Hydrophyllaceae | |
| Phacelia ramosissima var. latifolia | branching phacelia | Hydrophyllaceae | |
| Phacelia rotundifolia | roundleaf phacelia | Hydrophyllaceae | |
| Phacelia rupestris | rock phacelia | Hydrophyllaceae | |
| Phacelia saxicola | stonecrop phacelia | Hydrophyllaceae | |
| Phacelia scopulina | Debeque phacelia | Hydrophyllaceae | |
| Phacelia scopulina var. submutica | Debeque phacelia | Hydrophyllaceae | |
| Phacelia sericea | silky phacelia | Hydrophyllaceae | |
| Phacelia sericea ssp. ciliosa | silky phacelia | Hydrophyllaceae | |
| Phacelia serrata | saw phacelia | Hydrophyllaceae | |
| Phacelia tanacetifolia | lacy phacelia | Hydrophyllaceae | |
| Phacelia vallis-mortae | Death Valley phacelia | Hydrophyllaceae | |
| Phacelia vallis-mortae var. vallis-mortae | Death Valley phacelia | Hydrophyllaceae | |
| Phacelia welshii | Welsh's phacelia | Hydrophyllaceae | |
| Phalaris | canarygrass | Poaceae | |
| Phalaris angusta | timothy canarygrass | Poaceae | |
| Phalaris aquatica | bulbous canarygrass | Poaceae | |
| Phalaris arundinacea | reed canarygrass | Poaceae | |
| Phalaris canariensis | annual canarygrass | Poaceae | |
| Phalaris caroliniana | Carolina canarygrass | Poaceae | |
| Phalaris minor | littleseed canarygrass | Poaceae | |
| Phalaris paradoxa | hood canarygrass | Poaceae | |
| Phanerophlebia | phanerophlebia | Dryopteridaceae | |
| Phanerophlebia auriculata | eared veinfern | Dryopteridaceae | |
| Phaseolus | bean | Fabaceae | |
| Phaseolus acutifolius | tepary bean | Fabaceae | |
| Phaseolus acutifolius var. acutifolius | tepary bean | Fabaceae | |
| Phaseolus acutifolius var. latifolius | tepary bean | Fabaceae | |
| Phaseolus acutifolius var. tenuifolius | tepary bean | Fabaceae | |
| Phaseolus angustissimus | slimleaf bean | Fabaceae | |
| Phaseolus filiformis | slimjim bean | Fabaceae | |
| Phaseolus maculatus | spotted bean | Fabaceae | |
| Phaseolus parvulus | Pinos Altos Mountain bean | Fabaceae | |
| Phaseolus pedicellatus | Sonoran bean | Fabaceae | |
| Phaseolus pedicellatus var. grayanus | Gray's bean | Fabaceae | |
| Phaseolus ritensis | Santa Rita Mountain bean | Fabaceae | |
| Phemeranthus | Portulacaceae | ||
| Phemeranthus aurantiacus | orange fameflower | Portulacaceae | |
| Phemeranthus brevifolius | pygmy fameflower | Portulacaceae | |
| Phemeranthus confertiflorus | New Mexico fameflower | Portulacaceae | |
| Phemeranthus humilis | Pinos Altos fameflower | Portulacaceae | |
| Phemeranthus marginatus | tepic fameflower | Portulacaceae | |
| Phemeranthus validulus | Tusayan fameflower | Portulacaceae | |
| Philadelphus | mock orange | Hydrangeaceae | |
| Philadelphus argenteus | silver mock orange | Hydrangeaceae | |
| Philadelphus argyrocalyx | silvercup mock orange | Hydrangeaceae | |
| Philadelphus crinitus | Trans-Pecos mock orange | Hydrangeaceae | |
| Philadelphus maculatus | spotted mock orange | Hydrangeaceae | |
| Philadelphus madrensis | desert mountain mock orange | Hydrangeaceae | |
| Philadelphus microphyllus | littleleaf mock orange | Hydrangeaceae | |
| Philadelphus palmeri | Palmer's mock orange | Hydrangeaceae | |
| Philadelphus serpyllifolius | thymeleaf mock orange | Hydrangeaceae | |
| Phleum | timothy | Poaceae | |
| Phleum alpinum | alpine timothy | Poaceae | |
| Phleum pratense | timothy | Poaceae | |
| Phlox | phlox | Polemoniaceae | |
| Phlox amabilis | Arizona phlox | Polemoniaceae | |
| Phlox austromontana | mountain phlox | Polemoniaceae | |
| Phlox austromontana ssp. austromontana | mountain phlox | Polemoniaceae | |
| Phlox austromontana ssp. densa | dense mountain phlox | Polemoniaceae | |
| Phlox austromontana ssp. prostrata | prostrate mountain phlox | Polemoniaceae | |
| Phlox cluteana | Navajo Mountain phlox | Polemoniaceae | |
| Phlox diffusa | spreading phlox | Polemoniaceae | |
| Phlox diffusa ssp. subcarinata | spreading phlox | Polemoniaceae | |
| Phlox griseola | grayleaf phlox | Polemoniaceae | |
| Phlox griseola ssp. griseola | grayleaf phlox | Polemoniaceae | |
| Phlox hoodii | spiny phlox | Polemoniaceae | |
| Phlox hoodii ssp. canescens | carpet phlox | Polemoniaceae | |
| Phlox hoodii ssp. hoodii | spiny phlox | Polemoniaceae | |
| Phlox hoodii ssp. lanata | carpet phlox | Polemoniaceae | |
| Phlox longifolia | longleaf phlox | Polemoniaceae | |
| Phlox longifolia ssp. brevifolia | longleaf phlox | Polemoniaceae | |
| Phlox longifolia ssp. longifolia | longleaf phlox | Polemoniaceae | |
| Phlox speciosa | showy phlox | Polemoniaceae | |
| Phlox speciosa ssp. woodhousei | Woodhouse's phlox | Polemoniaceae | |
| Phlox stansburyi | cold-desert phlox | Polemoniaceae | |
| Phlox stansburyi ssp. stansburyi | cold-desert phlox | Polemoniaceae | |
| Phlox tenuifolia | Santa Catalina Mountain phlox | Polemoniaceae | |
| Phlox triovulata | threeseed phlox | Polemoniaceae | |
| Phlox viridis | green phlox | Polemoniaceae | |
| Phlox viridis ssp. compacta | green phlox | Polemoniaceae | |
| Phlox viridis ssp. longipes | green phlox | Polemoniaceae | |
| Phlox viscida | sticky phlox | Polemoniaceae | |
| Phoenix | date palm | Arecaceae | |
| Phoenix dactylifera | date palm | Arecaceae | |
| Pholisma | pholisma | Lennoaceae | |
| Pholisma arenarium | desert christmas tree | Lennoaceae | |
| Pholisma sonorae | sandfood | Lennoaceae | |
| Pholistoma | fiestaflower | Hydrophyllaceae | |
| Pholistoma auritum | blue fiestaflower | Hydrophyllaceae | |
| Pholistoma auritum var. arizonicum | Arizona fiestaflower | Hydrophyllaceae | |
| Pholistoma auritum var. auritum | blue fiestaflower | Hydrophyllaceae | |
| Phoradendron | mistletoe | Viscaceae | |
| Phoradendron californicum | mesquite mistletoe | Viscaceae | |
| Phoradendron capitellatum | downy mistletoe | Viscaceae | |
| Phoradendron coryae | Cory's mistletoe | Viscaceae | |
| Phoradendron densum | dense mistletoe | Viscaceae | |
| Phoradendron juniperinum | juniper mistletoe | Viscaceae | |
| Phoradendron macrophyllum | Colorado Desert mistletoe | Viscaceae | |
| Phoradendron macrophyllum ssp. macrophyllum | Colorado Desert mistletoe | Viscaceae | |
| Phoradendron pauciflorum | fir mistletoe | Viscaceae | |
| Phragmites | reed | Poaceae | |
| Phragmites australis | common reed | Poaceae | |
| Phyla | fogfruit | Verbenaceae | |
| Phyla cuneifolia | wedgeleaf | Verbenaceae | |
| Phyla lanceolata | lanceleaf fogfruit | Verbenaceae | |
| Phyla nodiflora | turkey tangle fogfruit | Verbenaceae | |
| Phyllanthus | leafflower | Euphorbiaceae | |
| Phyllanthus polygonoides | smartweed leaf-flower | Euphorbiaceae | |
| Phyllodoce | mountainheath | Ericaceae | |
| Phyllodoce empetriformis | pink mountainheath | Ericaceae | |
| Physalis | groundcherry | Solanaceae | |
| Physalis acutifolia | sharpleaf groundcherry | Solanaceae | |
| Physalis angulata | cutleaf groundcherry | Solanaceae | |
| Physalis caudella | southwestern groundcherry | Solanaceae | |
| Physalis crassifolia | yellow nightshade groundcherry | Solanaceae | |
| Physalis crassifolia var. crassifolia | yellow nightshade groundcherry | Solanaceae | |
| Physalis crassifolia var. versicolor | yellow nightshade groundcherry | Solanaceae | |
| Physalis hederifolia | ivyleaf groundcherry | Solanaceae | |
| Physalis hederifolia var. fendleri | Fendler's groundcherry | Solanaceae | |
| Physalis hederifolia var. hederifolia | ivyleaf groundcherry | Solanaceae | |
| Physalis heterophylla | clammy groundcherry | Solanaceae | |
| Physalis heterophylla var. heterophylla | clammy groundcherry | Solanaceae | |
| Physalis hispida | prairie groundcherry | Solanaceae | |
| Physalis latiphysa | broadleaf groundcherry | Solanaceae | |
| Physalis longifolia | longleaf groundcherry | Solanaceae | |
| Physalis longifolia var. longifolia | longleaf groundcherry | Solanaceae | |
| Physalis philadelphica | Mexican groundcherry | Solanaceae | |
| Physalis philadelphica var. immaculata | Mexican groundcherry | Solanaceae | |
| Physalis pubescens | husk tomato | Solanaceae | |
| Physalis pubescens var. integrifolia | husk tomato | Solanaceae | |
| Physalis subulata | Chihuahuan groundcherry | Solanaceae | |
| Physalis subulata var. neomexicana | New Mexican groundcherry | Solanaceae | |
| Physaria | twinpod | Brassicaceae | |
| Physaria chambersii | Chambers' twinpod | Brassicaceae | |
| Physaria newberryi | Newberry's twinpod | Brassicaceae | |
| Physaria newberryi var. newberryi | Newberry's twinpod | Brassicaceae | |
| Physaria newberryi var. racemosa | Newberry's twinpod | Brassicaceae | |
| Physocarpus | ninebark | Rosaceae | |
| Physocarpus monogynus | mountain ninebark | Rosaceae | |
| Phytolacca | pokeweed | Phytolaccaceae | |
| Phytolacca americana | American pokeweed | Phytolaccaceae | |
| Phytolacca americana var. americana | American pokeweed | Phytolaccaceae | |
| Phytolacca icosandra | tropical pokeweed | Phytolaccaceae | |
| Phytolacca octandra | red inkplant | Phytolaccaceae | |
| Picea | spruce | Pinaceae | |
| Picea engelmannii | Engelmann spruce | Pinaceae | |
| Picea engelmannii var. engelmannii | Engelmann spruce | Pinaceae | |
| Picea engelmannii var. mexicana | Pinaceae | ||
| Picea pungens | blue spruce | Pinaceae | |
| Picradeniopsis | bahia | Asteraceae | |
| Picradeniopsis oppositifolia | oppositeleaf bahia | Asteraceae | |
| Picradeniopsis woodhousei | Woodhouse's bahia | Asteraceae | |
| Picrothamnus | bud sagebrush | Asteraceae | |
| Picrothamnus desertorum | bud sagebrush | Asteraceae | |
| Pilostyles | stemsucker | Rafflesiaceae | |
| Pilostyles thurberi | Thurber's stemsucker | Rafflesiaceae | |
| Pinaropappus | rocklettuce | Asteraceae | |
| Pinaropappus roseus | white rocklettuce | Asteraceae | |
| Pinaropappus roseus var. foliosus | white rocklettuce | Asteraceae | |
| Pinus | pine | Pinaceae | |
| Pinus aristata | bristlecone pine | Pinaceae | |
| Pinus arizonica | Arizona pine | Pinaceae | |
| Pinus arizonica var. arizonica | Arizona pine | Pinaceae | |
| Pinus arizonica var. stormiae | Arizona pine | Pinaceae | |
| Pinus discolor | border pinyon | Pinaceae | |
| Pinus edulis | twoneedle pinyon | Pinaceae | |
| Pinus engelmannii | Apache pine | Pinaceae | |
| Pinus flexilis | limber pine | Pinaceae | |
| Pinus leiophylla | Chihuahuan pine | Pinaceae | |
| Pinus leiophylla var. chihuahuana | Chihuahuan pine | Pinaceae | |
| Pinus monophylla | singleleaf pinyon | Pinaceae | |
| Pinus monophylla var. fallax | singleleaf pinyon | Pinaceae | |
| Pinus monophylla var. monophylla | singleleaf pinyon | Pinaceae | |
| Pinus ponderosa | ponderosa pine | Pinaceae | |
| Pinus ponderosa var. scopulorum | ponderosa pine | Pinaceae | |
| Pinus strobiformis | southwestern white pine | Pinaceae | |
| Piptatherum | ricegrass | Poaceae | |
| Piptatherum micranthum | littleseed ricegrass | Poaceae | |
| Piptatherum miliaceum | smilograss | Poaceae | |
| Piptochaetium | speargrass | Poaceae | |
| Piptochaetium fimbriatum | pinyon ricegrass | Poaceae | |
| Piptochaetium pringlei | Pringle's speargrass | Poaceae | |
| Pisonia | catchbirdtree | Nyctaginaceae | |
| Pisonia capitata | Mexican devil's-claws | Nyctaginaceae | |
| Pistia | pistia | Araceae | |
| Pistia stratiotes | water lettuce | Araceae | |
| Plagiobothrys | popcornflower | Boraginaceae | |
| Plagiobothrys arizonicus | Arizona popcornflower | Boraginaceae | |
| Plagiobothrys collinus | Cooper's popcornflower | Boraginaceae | |
| Plagiobothrys collinus var. fulvescens | Cooper's popcornflower | Boraginaceae | |
| Plagiobothrys jonesii | Mojave popcornflower | Boraginaceae | |
| Plagiobothrys pringlei | Pringle's popcornflower | Boraginaceae | |
| Plagiobothrys scouleri | Scouler's popcornflower | Boraginaceae | |
| Plagiobothrys scouleri var. hispidulus | sleeping popcornflower | Boraginaceae | |
| Plagiobothrys tenellus | Pacific popcornflower | Boraginaceae | |
| Plantago | plantain | Plantaginaceae | |
| Plantago argyrea | saltmeadow plantain | Plantaginaceae | |
| Plantago australis | Mexican plantain | Plantaginaceae | |
| Plantago australis ssp. hirtella | Mexican plantain | Plantaginaceae | |
| Plantago elongata | prairie plantain | Plantaginaceae | |
| Plantago elongata ssp. elongata | prairie plantain | Plantaginaceae | |
| Plantago eriopoda | redwool plantain | Plantaginaceae | |
| Plantago lanceolata | narrowleaf plantain | Plantaginaceae | |
| Plantago major | common plantain | Plantaginaceae | |
| Plantago ovata | desert Indianwheat | Plantaginaceae | |
| Plantago patagonica | woolly plantain | Plantaginaceae | |
| Plantago rhodosperma | redseed plantain | Plantaginaceae | |
| Plantago tweedyi | Tweedy's plantain | Plantaginaceae | |
| Plantago virginica | Virginia plantain | Plantaginaceae | |
| Plantago wrightiana | Wright's plantain | Plantaginaceae | |
| Platanthera | fringed orchid | Orchidaceae | |
| Platanthera aquilonis | northern green orchid | Orchidaceae | |
| Platanthera dilatata | scentbottle | Orchidaceae | |
| Platanthera dilatata var. leucostachys | Sierra bog orchid | Orchidaceae | |
| Platanthera gracilis | lax-flowered green orchid | Orchidaceae | |
| Platanthera limosa | Thurber's bog orchid | Orchidaceae | |
| Platanthera purpurascens | purple-petal bog orchid | Orchidaceae | |
| Platanthera sparsiflora | sparse-flowered bog orchid | Orchidaceae | |
| Platanthera sparsiflora var. ensifolia | sparse-flowered bog orchid | Orchidaceae | |
| Platanthera sparsiflora var. sparsiflora | sparse-flowered bog orchid | Orchidaceae | |
| Platanthera stricta | slender bog orchid | Orchidaceae | |
| Platanthera zothecina | alcove bog orchid | Orchidaceae | |
| Platanus | sycamore | Platanaceae | |
| Platanus wrightii | Arizona sycamore | Platanaceae | |
| Platyschkuhria | basindaisy | Asteraceae | |
| Platyschkuhria integrifolia | basindaisy | Asteraceae | |
| Platyschkuhria integrifolia var. oblongifolia | oblongleaf basindaisy | Asteraceae | |
| Platystemon | creamcups | Papaveraceae | |
| Platystemon californicus | creamcups | Papaveraceae | |
| Plectritis | seablush | Valerianaceae | |
| Plectritis ciliosa | longspur seablush | Valerianaceae | |
| Plectritis ciliosa ssp. ciliosa | longspur seablush | Valerianaceae | |
| Plectritis ciliosa ssp. insignis | longspur seablush | Valerianaceae | |
| Pleiacanthus | Asteraceae | ||
| Pleiacanthus spinosus | thorn skeletonweed | Asteraceae | |
| Pleopeltis | scaly polypody | Polypodiaceae | |
| Pleopeltis riograndensis | Rio Grande scaly polypody | Polypodiaceae | |
| Pleuraphis | galleta grass | Poaceae | |
| Pleuraphis jamesii | James' galleta | Poaceae | |
| Pleuraphis mutica | tobosagrass | Poaceae | |
| Pleuraphis rigida | big galleta | Poaceae | |
| Pleurocoronis | pleurocoronis | Asteraceae | |
| Pleurocoronis pluriseta | bush arrowleaf | Asteraceae | |
| Pluchea | camphorweed | Asteraceae | |
| Pluchea odorata | sweetscent | Asteraceae | |
| Pluchea odorata var. odorata | sweetscent | Asteraceae | |
| Pluchea sericea | arrowweed | Asteraceae | |
| Plumbago | leadwort | Plumbaginaceae | |
| Plumbago scandens | doctorbush | Plumbaginaceae | |
| Poa | bluegrass | Poaceae | |
| Poa annua | annual bluegrass | Poaceae | |
| Poa bigelovii | Bigelow's bluegrass | Poaceae | |
| Poa bulbosa | bulbous bluegrass | Poaceae | |
| Poa compressa | Canada bluegrass | Poaceae | |
| Poa fendleriana | muttongrass | Poaceae | |
| Poa fendleriana ssp. albescens | muttongrass | Poaceae | |
| Poa fendleriana ssp. fendleriana | muttongrass | Poaceae | |
| Poa fendleriana ssp. longiligula | muttongrass | Poaceae | |
| Poa glauca | glaucous bluegrass | Poaceae | |
| Poa glauca ssp. rupicola | timberline bluegrass | Poaceae | |
| Poa leptocoma | marsh bluegrass | Poaceae | |
| Poa nemoralis | wood bluegrass | Poaceae | |
| Poa nemoralis ssp. interior | inland bluegrass | Poaceae | |
| Poa occidentalis | New Mexico bluegrass | Poaceae | |
| Poa palustris | fowl bluegrass | Poaceae | |
| Poa pratensis | Kentucky bluegrass | Poaceae | |
| Poa pratensis ssp. pratensis | Kentucky bluegrass | Poaceae | |
| Poa reflexa | nodding bluegrass | Poaceae | |
| Poa secunda | Sandberg bluegrass | Poaceae | |
| Polanisia | clammyweed | Capparaceae | |
| Polanisia dodecandra | redwhisker clammyweed | Capparaceae | |
| Polanisia dodecandra ssp. dodecandra | redwhisker clammyweed | Capparaceae | |
| Polanisia dodecandra ssp. trachysperma | sandyseed clammyweed | Capparaceae | |
| Polemonium | Jacob's-ladder | Polemoniaceae | |
| Polemonium foliosissimum | towering Jacob's-ladder | Polemoniaceae | |
| Polemonium foliosissimum var. flavum | yellow Jacob's-ladder | Polemoniaceae | |
| Polemonium foliosissimum var. foliosissimum | towering Jacob's-ladder | Polemoniaceae | |
| Polemonium pauciflorum | fewflower Jacob's-ladder | Polemoniaceae | |
| Polemonium pauciflorum ssp. hinckleyi | Hinckley's polemonium | Polemoniaceae | |
| Polemonium pauciflorum ssp. pauciflorum | fewflower Jacob's-ladder | Polemoniaceae | |
| Polemonium pulcherrimum | Jacob's-ladder | Polemoniaceae | |
| Polemonium pulcherrimum ssp. delicatum | Jacob's-ladder | Polemoniaceae | |
| Polemonium viscosum | sticky polemonium | Polemoniaceae | |
| Poliomintha | rosemary-mint | Lamiaceae | |
| Poliomintha incana | frosted mint | Lamiaceae | |
| Polygala | polygala | Polygalaceae | |
| Polygala acanthoclada | desert polygala | Polygalaceae | |
| Polygala alba | white milkwort | Polygalaceae | |
| Polygala barbeyana | blue milkwort | Polygalaceae | |
| Polygala glochidiata | tropical milkwort | Polygalaceae | |
| Polygala hemipterocarpa | winged milkwort | Polygalaceae | |
| Polygala intermontana | Intermountain milkwort | Polygalaceae | |
| Polygala lindheimeri | shrubby milkwort | Polygalaceae | |
| Polygala lindheimeri var. parvifolia | shrubby milkwort | Polygalaceae | |
| Polygala macradenia | glandleaf milkwort | Polygalaceae | |
| Polygala obscura | velvetseed milkwort | Polygalaceae | |
| Polygala piliophora | Huachuca Mountain milkwort | Polygalaceae | |
| Polygala rusbyi | Rusby's milkwort | Polygalaceae | |
| Polygala scoparioides | broom milkwort | Polygalaceae | |
| Polygala subspinosa | spiny milkwort | Polygalaceae | |
| Polygonatum | Solomon's seal | Liliaceae | |
| Polygonatum cobrense | McKittrick's Solomon's seal | Liliaceae | |
| Polygonum | knotweed | Polygonaceae | |
| Polygonum amphibium | water knotweed | Polygonaceae | |
| Polygonum amphibium var. emersum | longroot smartweed | Polygonaceae | |
| Polygonum amphibium var. stipulaceum | water smartweed | Polygonaceae | |
| Polygonum arenastrum | oval-leaf knotweed | Polygonaceae | |
| Polygonum argyrocoleon | silversheath knotweed | Polygonaceae | |
| Polygonum aviculare | prostrate knotweed | Polygonaceae | |
| Polygonum bistortoides | American bistort | Polygonaceae | |
| Polygonum buxiforme | box knotweed | Polygonaceae | |
| Polygonum convolvulus | black bindweed | Polygonaceae | |
| Polygonum convolvulus var. convolvulus | black bindweed | Polygonaceae | |
| Polygonum douglasii | Douglas' knotweed | Polygonaceae | |
| Polygonum douglasii ssp. douglasii | Douglas' knotweed | Polygonaceae | |
| Polygonum douglasii ssp. johnstonii | Johnston's knotweed | Polygonaceae | |
| Polygonum hydropiperoides | swamp smartweed | Polygonaceae | |
| Polygonum lapathifolium | curlytop knotweed | Polygonaceae | |
| Polygonum minimum | broadleaf knotweed | Polygonaceae | |
| Polygonum pensylvanicum | Pennsylvania smartweed | Polygonaceae | |
| Polygonum persicaria | spotted ladysthumb | Polygonaceae | |
| Polygonum polygaloides | milkwort knotweed | Polygonaceae | |
| Polygonum polygaloides ssp. confertiflorum | fruitleaf knotweed | Polygonaceae | |
| Polygonum polygaloides ssp. kelloggii | Kellogg's knotweed | Polygonaceae | |
| Polygonum punctatum | dotted smartweed | Polygonaceae | |
| Polygonum punctatum var. confertiflorum | dotted smartweed | Polygonaceae | |
| Polygonum ramosissimum | bushy knotweed | Polygonaceae | |
| Polygonum ramosissimum var. ramosissimum | bushy knotweed | Polygonaceae | |
| Polygonum viviparum | alpine bistort | Polygonaceae | |
| Polypodium | polypody | Polypodiaceae | |
| Polypodium glycyrrhiza | licorice fern | Polypodiaceae | |
| Polypodium hesperium | western polypody | Polypodiaceae | |
| Polypogon | rabbitsfoot grass | Poaceae | |
| Polypogon australis | Chilean rabbitsfoot grass | Poaceae | |
| Polypogon elongatus | streambank rabbitsfoot grass | Poaceae | |
| Polypogon interruptus | ditch rabbitsfoot grass | Poaceae | |
| Polypogon monspeliensis | annual rabbitsfoot grass | Poaceae | |
| Polypogon viridis | beardless rabbitsfoot grass | Poaceae | |
| Polystichum | hollyfern | Dryopteridaceae | |
| Polystichum lonchitis | northern hollyfern | Dryopteridaceae | |
| Polystichum scopulinum | mountain hollyfern | Dryopteridaceae | |
| Pomaria | Fabaceae | ||
| Pomaria jamesii | James' holdback | Fabaceae | |
| Populus | cottonwood | Salicaceae | |
| Populus acuminata | lanceleaf cottonwood | Salicaceae | |
| Populus angustifolia | narrowleaf cottonwood | Salicaceae | |
| Populus deltoides | eastern cottonwood | Salicaceae | |
| Populus deltoides ssp. wislizeni | Rio Grande cottonwood | Salicaceae | |
| Populus fremontii | Fremont cottonwood | Salicaceae | |
| Populus fremontii ssp. fremontii | Fremont cottonwood | Salicaceae | |
| Populus fremontii ssp. mesetae | Fremont cottonwood | Salicaceae | |
| Populus hinckleyana | Salicaceae | ||
| Populus nigra | Lombardy poplar | Salicaceae | |
| Populus parryi | Salicaceae | ||
| Populus tremuloides | quaking aspen | Salicaceae | |
| Porophyllum | poreleaf | Asteraceae | |
| Porophyllum gracile | slender poreleaf | Asteraceae | |
| Porophyllum ruderale | yerba porosa | Asteraceae | |
| Porophyllum ruderale ssp. macrocephalum | yerba porosa | Asteraceae | |
| Porterella | porterella | Campanulaceae | |
| Porterella carnosula | fleshy porterella | Campanulaceae | |
| Portulaca | purslane | Portulacaceae | |
| Portulaca halimoides | silkcotton purslane | Portulacaceae | |
| Portulaca oleracea | little hogweed | Portulacaceae | |
| Portulaca pilosa | kiss me quick | Portulacaceae | |
| Portulaca suffrutescens | shrubby purslane | Portulacaceae | |
| Portulaca umbraticola | wingpod purslane | Portulacaceae | |
| Portulaca umbraticola ssp. umbraticola | wingpod purslane | Portulacaceae | |
| Potamogeton | pondweed | Potamogetonaceae | |
| Potamogeton crispus | curly pondweed | Potamogetonaceae | |
| Potamogeton diversifolius | waterthread pondweed | Potamogetonaceae | |
| Potamogeton foliosus | leafy pondweed | Potamogetonaceae | |
| Potamogeton foliosus ssp. foliosus | leafy pondweed | Potamogetonaceae | |
| Potamogeton gramineus | variableleaf pondweed | Potamogetonaceae | |
| Potamogeton illinoensis | Illinois pondweed | Potamogetonaceae | |
| Potamogeton natans | floating pondweed | Potamogetonaceae | |
| Potamogeton nodosus | longleaf pondweed | Potamogetonaceae | |
| Potamogeton pusillus | small pondweed | Potamogetonaceae | |
| Potamogeton pusillus ssp. pusillus | small pondweed | Potamogetonaceae | |
| Potamogeton pusillus ssp. tenuissimus | small pondweed | Potamogetonaceae | |
| Potamogeton richardsonii | Richardson's pondweed | Potamogetonaceae | |
| Potamogeton spathuliformis | Potamogetonaceae | ||
| Potentilla | cinquefoil | Rosaceae | |
| Potentilla albiflora | whiteflower cinquefoil | Rosaceae | |
| Potentilla argentea | silver cinquefoil | Rosaceae | |
| Potentilla argentea var. argentea | silver cinquefoil | Rosaceae | |
| Potentilla arguta | tall cinquefoil | Rosaceae | |
| Potentilla arguta ssp. convallaria | cream cinquefoil | Rosaceae | |
| Potentilla biennis | biennial cinquefoil | Rosaceae | |
| Potentilla concinna | elegant cinquefoil | Rosaceae | |
| Potentilla concinna var. proxima | elegant cinquefoil | Rosaceae | |
| Potentilla crinita | bearded cinquefoil | Rosaceae | |
| Potentilla crinita var. crinita | bearded cinquefoil | Rosaceae | |
| Potentilla crinita var. lemmonii | Lemmon's cinquefoil | Rosaceae | |
| Potentilla diversifolia | varileaf cinquefoil | Rosaceae | |
| Potentilla diversifolia var. diversifolia | varileaf cinquefoil | Rosaceae | |
| Potentilla glandulosa | sticky cinquefoil | Rosaceae | |
| Potentilla glandulosa ssp. arizonica | Arizona cinquefoil | Rosaceae | |
| Potentilla glandulosa ssp. glabrata | sticky cinquefoil | Rosaceae | |
| Potentilla gracilis | slender cinquefoil | Rosaceae | |
| Potentilla gracilis var. fastigiata | slender cinquefoil | Rosaceae | |
| Potentilla hippiana | woolly cinquefoil | Rosaceae | |
| Potentilla hippiana var. hippiana | woolly cinquefoil | Rosaceae | |
| Potentilla nivea | snow cinquefoil | Rosaceae | |
| Potentilla nivea var. pentaphylla | fiveleaf cinquefoil | Rosaceae | |
| Potentilla norvegica | Norwegian cinquefoil | Rosaceae | |
| Potentilla norvegica ssp. monspeliensis | Norwegian cinquefoil | Rosaceae | |
| Potentilla pectinisecta | combleaf cinquefoil | Rosaceae | |
| Potentilla pensylvanica | Pennsylvania cinquefoil | Rosaceae | |
| Potentilla pensylvanica var. pensylvanica | Pennsylvania cinquefoil | Rosaceae | |
| Potentilla plattensis | Platte River cinquefoil | Rosaceae | |
| Potentilla pulcherrima | beautiful cinquefoil | Rosaceae | |
| Potentilla rivalis | brook cinquefoil | Rosaceae | |
| Potentilla rubida | Chihuahuan cinquefoil | Rosaceae | |
| Potentilla subviscosa | Navajo cinquefoil | Rosaceae | |
| Potentilla subviscosa var. ramulosa | Navajo cinquefoil | Rosaceae | |
| Potentilla subviscosa var. subviscosa | Navajo cinquefoil | Rosaceae | |
| Potentilla thurberi | scarlet cinquefoil | Rosaceae | |
| Potentilla thurberi var. atrorubens | scarlet cinquefoil | Rosaceae | |
| Potentilla thurberi var. sanguinea | scarlet cinquefoil | Rosaceae | |
| Potentilla thurberi var. thurberi | scarlet cinquefoil | Rosaceae | |
| Potentilla wheeleri | Kern cinquefoil | Rosaceae | |
| Prenanthella | prenanthella | Asteraceae | |
| Prenanthella exigua | brightwhite | Asteraceae | |
| Primula | primrose | Primulaceae | |
| Primula parryi | Parry's primrose | Primulaceae | |
| Primula rusbyi | Rusby's primrose | Primulaceae | |
| Primula specuicola | cavedwelling primrose | Primulaceae | |
| Proboscidea | unicorn-plant | Pedaliaceae | |
| Proboscidea althaeifolia | desert unicorn-plant | Pedaliaceae | |
| Proboscidea parviflora | doubleclaw | Pedaliaceae | |
| Proboscidea parviflora ssp. parviflora | unicorn plant, devil's claw | Pedaliaceae | |
| Proboscidea parviflora ssp. parviflora var. hohokamiana | Pedaliaceae | ||
| Proboscidea parviflora ssp. parviflora var. parviflora | doubleclaw | Pedaliaceae | |
| Prosartes | Liliaceae | ||
| Prosartes trachycarpa | roughfruit fairybells | Liliaceae | |
| Prosopis | mesquite | Fabaceae | |
| Prosopis farcta | Syrian mesquite | Fabaceae | |
| Prosopis glandulosa | honey mesquite | Fabaceae | |
| Prosopis glandulosa var. torreyana | western honey mesquite | Fabaceae | |
| Prosopis pubescens | screwbean mesquite | Fabaceae | |
| Prosopis velutina | velvet mesquite | Fabaceae | |
| Prunella | selfheal | Lamiaceae | |
| Prunella vulgaris | common selfheal | Lamiaceae | |
| Prunella vulgaris ssp. lanceolata | lance selfheal | Lamiaceae | |
| Prunus | plum | Rosaceae | |
| Prunus americana | American plum | Rosaceae | |
| Prunus emarginata | bitter cherry | Rosaceae | |
| Prunus emarginata var. emarginata | bitter cherry | Rosaceae | |
| Prunus fasciculata | desert almond | Rosaceae | |
| Prunus fasciculata var. fasciculata | desert almond | Rosaceae | |
| Prunus persica | peach | Rosaceae | |
| Prunus persica var. persica | peach | Rosaceae | |
| Prunus serotina | black cherry | Rosaceae | |
| Prunus serotina var. rufula | black cherry | Rosaceae | |
| Prunus serotina var. virens | black cherry | Rosaceae | |
| Prunus virginiana | chokecherry | Rosaceae | |
| Prunus virginiana var. demissa | western chokecherry | Rosaceae | |
| Psacalium | Indianbush | Asteraceae | |
| Psacalium decompositum | desert Indianbush | Asteraceae | |
| Psathyrostachys | wildrye | Poaceae | |
| Psathyrostachys juncea | Russian wildrye | Poaceae | |
| Psathyrotes | turtleback | Asteraceae | |
| Psathyrotes annua | annual psathyrotes | Asteraceae | |
| Psathyrotes pilifera | hairybeast turtleback | Asteraceae | |
| Psathyrotes ramosissima | velvet turtleback | Asteraceae | |
| Pseudelymus | foxtail wheatgrass | Poaceae | |
| Pseudelymus saxicola | foxtail wheatgrass | Poaceae | |
| Pseudocymopterus | false springparsley | Apiaceae | |
| Pseudocymopterus montanus | alpine false springparsley | Apiaceae | |
| Pseudognaphalium | cudweed | Asteraceae | |
| Pseudognaphalium arizonicum | Arizona cudweed | Asteraceae | |
| Pseudognaphalium canescens | Wright's cudweed | Asteraceae | |
| Pseudognaphalium canescens ssp. canescens | Wright's cudweed | Asteraceae | |
| Pseudognaphalium jaliscense | Jalisco rabbit-tobacco | Asteraceae | |
| Pseudognaphalium leucocephalum | white cudweed | Asteraceae | |
| Pseudognaphalium luteoalbum | Jersey cudweed | Asteraceae | |
| Pseudognaphalium macounii | Macoun's cudweed | Asteraceae | |
| Pseudognaphalium pringlei | Pringle's cudweed | Asteraceae | |
| Pseudognaphalium stramineum | cottonbatting plant | Asteraceae | |
| Pseudoroegneria | wheatgrass | Poaceae | |
| Pseudoroegneria spicata | bluebunch wheatgrass | Poaceae | |
| Pseudoroegneria spicata ssp. spicata | bluebunch wheatgrass | Poaceae | |
| Pseudorontium | pseudorontium | Scrophulariaceae | |
| Pseudorontium cyathiferum | dog's-mouth | Scrophulariaceae | |
| Pseudostellaria | pseudostellaria | Caryophyllaceae | |
| Pseudostellaria jamesiana | tuber starwort | Caryophyllaceae | |
| Pseudotsuga | Douglas-fir | Pinaceae | |
| Pseudotsuga menziesii | Douglas-fir | Pinaceae | |
| Pseudotsuga menziesii var. glauca | Rocky Mountain Douglas-fir | Pinaceae | |
| Psilactis | tansyaster | Asteraceae | |
| Psilactis asteroides | New Mexico tansyaster | Asteraceae | |
| Psilactis gentryi | Mexican tansyaster | Asteraceae | |
| Psilostrophe | paperflower | Asteraceae | |
| Psilostrophe cooperi | whitestem paperflower | Asteraceae | |
| Psilostrophe sparsiflora | greenstem paperflower | Asteraceae | |
| Psilostrophe tagetina | woolly paperflower | Asteraceae | |
| Psilostrophe tagetina var. tagetina | woolly paperflower | Asteraceae | |
| Psilotum | whisk fern | Psilotaceae | |
| Psilotum nudum | whisk fern | Psilotaceae | |
| Psoralidium | scurfpea | Fabaceae | |
| Psoralidium junceum | rush lemonweed | Fabaceae | |
| Psoralidium lanceolatum | lemon scurfpea | Fabaceae | |
| Psoralidium tenuiflorum | slimflower scurfpea | Fabaceae | |
| Psorothamnus | dalea | Fabaceae | |
| Psorothamnus arborescens | Mojave indigobush | Fabaceae | |
| Psorothamnus arborescens var. pubescens | Mojave indigobush | Fabaceae | |
| Psorothamnus emoryi | dyebush | Fabaceae | |
| Psorothamnus fremontii | Fremont's dalea | Fabaceae | |
| Psorothamnus fremontii var. attenuatus | Fremont's dalea | Fabaceae | |
| Psorothamnus fremontii var. fremontii | Fremont's dalea | Fabaceae | |
| Psorothamnus schottii | Schott's dalea | Fabaceae | |
| Psorothamnus scoparius | broom dalea | Fabaceae | |
| Psorothamnus spinosus | smoketree | Fabaceae | |
| Psorothamnus thompsoniae | Thompson's dalea | Fabaceae | |
| Psorothamnus thompsoniae var. whitingii | Whiting's dalea | Fabaceae | |
| Ptelea | hoptree | Rutaceae | |
| Ptelea trifoliata | common hoptree | Rutaceae | |
| Ptelea trifoliata ssp. pallida | pallid hoptree | Rutaceae | |
| Ptelea trifoliata ssp. pallida var. cognata | pallid hoptree | Rutaceae | |
| Ptelea trifoliata ssp. pallida var. lutescens | pallid hoptree | Rutaceae | |
| Ptelea trifoliata ssp. pallida var. pallida | pallid hoptree | Rutaceae | |
| Ptelea trifoliata ssp. polyadenia | pallid hoptree | Rutaceae | |
| Pteridium | brackenfern | Dennstaedtiaceae | |
| Pteridium aquilinum | western brackenfern | Dennstaedtiaceae | |
| Pteridium aquilinum var. pubescens | hairy brackenfern | Dennstaedtiaceae | |
| Pterospora | pinedrops | Monotropaceae | |
| Pterospora andromedea | woodland pinedrops | Monotropaceae | |
| Pterostegia | pterostegia | Polygonaceae | |
| Pterostegia drymarioides | woodland pterostegia | Polygonaceae | |
| Pteryxia | wavewing | Apiaceae | |
| Pteryxia davidsonii | Davidson's wavewing | Apiaceae | |
| Pteryxia petraea | rockloving wavewing | Apiaceae | |
| Puccinellia | alkaligrass | Poaceae | |
| Puccinellia distans | weeping alkaligrass | Poaceae | |
| Puccinellia distans ssp. distans | weeping alkaligrass | Poaceae | |
| Puccinellia fasciculata | saltmarsh alkaligrass | Poaceae | |
| Puccinellia nuttalliana | Nuttall's alkaligrass | Poaceae | |
| Puccinellia parishii | bog alkaligrass | Poaceae | |
| Purshia | bitterbrush | Rosaceae | |
| Purshia glandulosa | desert bitterbrush | Rosaceae | |
| Purshia mexicana | Mexican cliffrose | Rosaceae | |
| Purshia pinkavae | Pinkava's cliffrose | Rosaceae | |
| Purshia stansburiana | Stansbury cliffrose | Rosaceae | |
| Purshia subintegra | Rosaceae | ||
| Purshia tridentata | antelope bitterbrush | Rosaceae | |
| Pyracantha | firethorn | Rosaceae | |
| Pyracantha koidzumii | Formosa firethorn | Rosaceae | |
| Pyrola | wintergreen | Pyrolaceae | |
| Pyrola chlorantha | greenflowered wintergreen | Pyrolaceae | |
| Pyrola elliptica | waxflower shinleaf | Pyrolaceae | |
| Pyrola minor | snowline wintergreen | Pyrolaceae | |
| Pyrola picta | whiteveined wintergreen | Pyrolaceae | |
| Pyrrhopappus | desert-chicory | Asteraceae | |
| Pyrrhopappus pauciflorus | smallflower desert-chicory | Asteraceae | |
| Pyrrocoma | goldenweed | Asteraceae | |
| Pyrrocoma crocea | curlyhead goldenweed | Asteraceae | |
| Pyrrocoma crocea var. genuflexa | curlyhead goldenweed | Asteraceae | |
| Q | |||
| Quercus | oak | Fagaceae | |
| Quercus ajoensis | Ajo Mountain scrub oak | Fagaceae | |
| Quercus arizonica | Arizona white oak | Fagaceae | |
| Quercus chrysolepis | canyon live oak | Fagaceae | |
| Quercus chrysolepis var. chrysolepis | canyon live oak | Fagaceae | |
| Quercus emoryi | Emory oak | Fagaceae | |
| Quercus gambelii | Gambel oak | Fagaceae | |
| Quercus gambelii var. gambelii | Gambel oak | Fagaceae | |
| Quercus grisea | gray oak | Fagaceae | |
| Quercus havardii | Havard oak | Fagaceae | |
| Quercus havardii var. havardii | Havard oak | Fagaceae | |
| Quercus hypoleucoides | silverleaf oak | Fagaceae | |
| Quercus oblongifolia | Mexican blue oak | Fagaceae | |
| Quercus organensis | Fagaceae | ||
| Quercus palmeri | Palmer oak | Fagaceae | |
| Quercus pauciloba | Fagaceae | ||
| Quercus pungens | pungent oak | Fagaceae | |
| Quercus rugosa | netleaf oak | Fagaceae | |
| Quercus toumeyi | Toumey oak | Fagaceae | |
| Quercus turbinella | Sonoran scrub oak | Fagaceae | |
| Quercus viminea | Sonoran oak | Fagaceae | |
| Quincula | quincula | Solanaceae | |
| Quincula lobata | Chinese lantern | Solanaceae | |
| R | |||
| Rafinesquia | plumeseed | Asteraceae | |
| Rafinesquia californica | California plumeseed | Asteraceae | |
| Rafinesquia neomexicana | New Mexico plumeseed | Asteraceae | |
| Ranunculus | buttercup | Ranunculaceae | |
| Ranunculus andersonii | Anderson's buttercup | Ranunculaceae | |
| Ranunculus andersonii var. tenellus | Anderson's buttercup | Ranunculaceae | |
| Ranunculus arizonicus | Arizona buttercup | Ranunculaceae | |
| Ranunculus cardiophyllus | heartleaf buttercup | Ranunculaceae | |
| Ranunculus cymbalaria | alkali buttercup | Ranunculaceae | |
| Ranunculus eschscholtzii | Eschscholtz's buttercup | Ranunculaceae | |
| Ranunculus eschscholtzii var. eschscholtzii | Eschscholtz's buttercup | Ranunculaceae | |
| Ranunculus eximius | tundra buttercup | Ranunculaceae | |
| Ranunculus flammula | greater creeping spearwort | Ranunculaceae | |
| Ranunculus flammula var. flammula | greater creeping spearwort | Ranunculaceae | |
| Ranunculus glaberrimus | sagebrush buttercup | Ranunculaceae | |
| Ranunculus glaberrimus var. ellipticus | elliptical buttercup | Ranunculaceae | |
| Ranunculus hebecarpus | delicate buttercup | Ranunculaceae | |
| Ranunculus hydrocharoides | frogbit buttercup | Ranunculaceae | |
| Ranunculus hydrocharoides var. hydrocharoides | frogbit buttercup | Ranunculaceae | |
| Ranunculus hydrocharoides var. stolonifer | frogbit buttercup | Ranunculaceae | |
| Ranunculus inamoenus | graceful buttercup | Ranunculaceae | |
| Ranunculus inamoenus var. alpeophilus | graceful buttercup | Ranunculaceae | |
| Ranunculus inamoenus var. inamoenus | graceful buttercup | Ranunculaceae | |
| Ranunculus inamoenus var. subaffinis | graceful buttercup | Ranunculaceae | |
| Ranunculus longirostris | longbeak buttercup | Ranunculaceae | |
| Ranunculus macounii | Macoun's buttercup | Ranunculaceae | |
| Ranunculus macranthus | large buttercup | Ranunculaceae | |
| Ranunculus oreogenes | Oregon buttercup | Ranunculaceae | |
| Ranunculus pedatifidus | surefoot buttercup | Ranunculaceae | |
| Ranunculus pedatifidus var. affinis | northern buttercup | Ranunculaceae | |
| Ranunculus pensylvanicus | Pennsylvania buttercup | Ranunculaceae | |
| Ranunculus petiolaris | Latin American buttercup | Ranunculaceae | |
| Ranunculus petiolaris var. arsenei | Arsene's buttercup | Ranunculaceae | |
| Ranunculus sceleratus | cursed buttercup | Ranunculaceae | |
| Ranunculus sceleratus var. multifidus | cursed buttercup | Ranunculaceae | |
| Ranunculus trichophyllus | threadleaf crowfoot | Ranunculaceae | |
| Ranunculus trichophyllus var. trichophyllus | threadleaf crowfoot | Ranunculaceae | |
| Ranunculus uncinatus | woodland buttercup | Ranunculaceae | |
| Ranunculus uncinatus var. uncinatus | woodland buttercup | Ranunculaceae | |
| Raphanus | radish | Brassicaceae | |
| Raphanus raphanistrum | wild radish | Brassicaceae | |
| Raphanus sativus | cultivated radish | Brassicaceae | |
| Ratibida | prairie coneflower | Asteraceae | |
| Ratibida columnifera | upright prairie coneflower | Asteraceae | |
| Ratibida tagetes | green prairie coneflower | Asteraceae | |
| Redfieldia | blowout grass | Poaceae | |
| Redfieldia flexuosa | blowout grass | Poaceae | |
| Reverchonia | reverchonia | Euphorbiaceae | |
| Reverchonia arenaria | sand reverchonia | Euphorbiaceae | |
| Rhamnus | buckthorn | Rhamnaceae | |
| Rhamnus crocea | redberry buckthorn | Rhamnaceae | |
| Rhamnus crocea ssp. crocea | redberry buckthorn | Rhamnaceae | |
| Rhamnus crocea ssp. pilosa | hollyleaf buckthorn | Rhamnaceae | |
| Rhamnus ilicifolia | hollyleaf redberry | Rhamnaceae | |
| Rhamnus serrata | sawleaf buckthorn | Rhamnaceae | |
| Rhinanthus | yellow rattle | Scrophulariaceae | |
| Rhinanthus minor | little yellow rattle | Scrophulariaceae | |
| Rhinanthus minor ssp. minor | little yellow rattle | Scrophulariaceae | |
| Rhodiola | stonecrop | Crassulaceae | |
| Rhodiola rhodantha | redpod stonecrop | Crassulaceae | |
| Rhus | sumac | Anacardiaceae | |
| Rhus glabra | smooth sumac | Anacardiaceae | |
| Rhus kearneyi | Kearney's sumac | Anacardiaceae | |
| Rhus lanceolata | prairie sumac | Anacardiaceae | |
| Rhus microphylla | littleleaf sumac | Anacardiaceae | |
| Rhus ovata | sugar sumac | Anacardiaceae | |
| Rhus trilobata | skunkbush sumac | Anacardiaceae | |
| Rhus trilobata var. anisophylla | skunkbush sumac | Anacardiaceae | |
| Rhus trilobata var. pilosissima | pubescent skunkbush sumac | Anacardiaceae | |
| Rhus trilobata var. quinata | skunkbush sumac | Anacardiaceae | |
| Rhus trilobata var. racemulosa | skunkbush sumac | Anacardiaceae | |
| Rhus trilobata var. simplicifolia | skunkbush sumac | Anacardiaceae | |
| Rhus trilobata var. trilobata | skunkbush sumac | Anacardiaceae | |
| Rhus virens | evergreen sumac | Anacardiaceae | |
| Rhus virens var. choriophylla | evergreen sumac | Anacardiaceae | |
| Rhynchosia | snoutbean | Fabaceae | |
| Rhynchosia edulis | Chihuahuan snoutbean | Fabaceae | |
| Rhynchosia precatoria | rosary snoutbean | Fabaceae | |
| Rhynchosia senna | Texas snoutbean | Fabaceae | |
| Rhynchosia senna var. texana | Texas snoutbean | Fabaceae | |
| Rhynchosida | rhynchosida | Malvaceae | |
| Rhynchosida physocalyx | buffpetal | Malvaceae | |
| Ribes | currant | Grossulariaceae | |
| Ribes aureum | golden currant | Grossulariaceae | |
| Ribes aureum var. aureum | golden currant | Grossulariaceae | |
| Ribes cereum | wax currant | Grossulariaceae | |
| Ribes cereum var. cereum | wax currant | Grossulariaceae | |
| Ribes cereum var. pedicellare | whisky currant | Grossulariaceae | |
| Ribes inerme | whitestem gooseberry | Grossulariaceae | |
| Ribes inerme var. inerme | whitestem gooseberry | Grossulariaceae | |
| Ribes leptanthum | trumpet gooseberry | Grossulariaceae | |
| Ribes montigenum | gooseberry currant | Grossulariaceae | |
| Ribes pinetorum | orange gooseberry | Grossulariaceae | |
| Ribes quercetorum | rock gooseberry | Grossulariaceae | |
| Ribes velutinum | desert gooseberry | Grossulariaceae | |
| Ribes velutinum var. velutinum | desert gooseberry | Grossulariaceae | |
| Ribes viscosissimum | sticky currant | Grossulariaceae | |
| Ribes wolfii | Wolf's currant | Grossulariaceae | |
| Ricinus | ricinus | Euphorbiaceae | |
| Ricinus communis | castorbean | Euphorbiaceae | |
| Rivina | rivina | Phytolaccaceae | |
| Rivina humilis | rougeplant | Phytolaccaceae | |
| Robinia | locust | Fabaceae | |
| Robinia neomexicana | New Mexico locust | Fabaceae | |
| Robinia neomexicana var. neomexicana | New Mexico locust | Fabaceae | |
| Robinia neomexicana var. rusbyi | Rusby's locust | Fabaceae | |
| Robinia pseudoacacia | black locust | Fabaceae | |
| Roldana | groundsel | Asteraceae | |
| Roldana hartwegii | Hartweg's groundsel | Asteraceae | |
| Rorippa | yellowcress | Brassicaceae | |
| Rorippa curvipes | bluntleaf yellowcress | Brassicaceae | |
| Rorippa curvipes var. curvipes | bluntleaf yellowcress | Brassicaceae | |
| Rorippa curvipes var. truncata | bluntleaf yellowcress | Brassicaceae | |
| Rorippa curvisiliqua | curvepod yellowcress | Brassicaceae | |
| Rorippa curvisiliqua var. orientalis | Oriental yellowcress | Brassicaceae | |
| Rorippa microtitis | Chihuahuan yellowcress | Brassicaceae | |
| Rorippa palustris | bog yellowcress | Brassicaceae | |
| Rorippa palustris ssp. fernaldiana | Fernald's yellowcress | Brassicaceae | |
| Rorippa palustris ssp. occidentalis | western bog yellowcress | Brassicaceae | |
| Rorippa sinuata | spreading yellowcress | Brassicaceae | |
| Rorippa sphaerocarpa | roundfruit yellowcress | Brassicaceae | |
| Rorippa sylvestris | creeping yellowcress | Brassicaceae | |
| Rosa | rose | Rosaceae | |
| Rosa stellata | desert rose | Rosaceae | |
| Rosa stellata ssp. abyssa | desert rose | Rosaceae | |
| Rosa stellata ssp. stellata | desert rose | Rosaceae | |
| Rosa woodsii | Woods' rose | Rosaceae | |
| Rosa woodsii var. woodsii | Woods' rose | Rosaceae | |
| Rostraria | hairgrass | Poaceae | |
| Rostraria cristata | Mediterranean hairgrass | Poaceae | |
| Rotala | rotala | Lythraceae | |
| Rotala ramosior | lowland rotala | Lythraceae | |
| Rubus | blackberry | Rosaceae | |
| Rubus arizonensis | Arizona dewberry | Rosaceae | |
| Rubus armeniacus | Himalayan blackberry | Rosaceae | |
| Rubus idaeus | American red raspberry | Rosaceae | |
| Rubus idaeus ssp. strigosus | grayleaf red raspberry | Rosaceae | |
| Rubus leucodermis | whitebark raspberry | Rosaceae | |
| Rubus leucodermis var. leucodermis | whitebark raspberry | Rosaceae | |
| Rubus neomexicanus | New Mexico raspberry | Rosaceae | |
| Rubus parviflorus | thimbleberry | Rosaceae | |
| Rubus parviflorus var. parviflorus | thimbleberry | Rosaceae | |
| Rudbeckia | coneflower | Asteraceae | |
| Rudbeckia laciniata | cutleaf coneflower | Asteraceae | |
| Rudbeckia laciniata var. ampla | cutleaf coneflower | Asteraceae | |
| Rudbeckia laciniata var. laciniata | cutleaf coneflower | Asteraceae | |
| Ruellia | wild petunia | Acanthaceae | |
| Ruellia nudiflora | violet wild petunia | Acanthaceae | |
| Ruellia nudiflora var. nudiflora | violet wild petunia | Acanthaceae | |
| Rumex | dock | Polygonaceae | |
| Rumex acetosella | common sheep sorrel | Polygonaceae | |
| Rumex altissimus | pale dock | Polygonaceae | |
| Rumex aquaticus | western dock | Polygonaceae | |
| Rumex aquaticus var. fenestratus | western dock | Polygonaceae | |
| Rumex conglomeratus | clustered dock | Polygonaceae | |
| Rumex crispus | curly dock | Polygonaceae | |
| Rumex crispus ssp. crispus | curly dock | Polygonaceae | |
| Rumex densiflorus | denseflowered dock | Polygonaceae | |
| Rumex dentatus | toothed dock | Polygonaceae | |
| Rumex hymenosepalus | canaigre dock | Polygonaceae | |
| Rumex maritimus | golden dock | Polygonaceae | |
| Rumex nematopodus | Arizona dock | Polygonaceae | |
| Rumex obtusifolius | bitter dock | Polygonaceae | |
| Rumex orthoneurus | Chiricahua Mountain dock | Polygonaceae | |
| Rumex salicifolius | willow dock | Polygonaceae | |
| Rumex salicifolius var. denticulatus | toothed willow dock | Polygonaceae | |
| Rumex salicifolius var. mexicanus | Mexican dock | Polygonaceae | |
| Rumex stenophyllus | narrowleaf dock | Polygonaceae | |
| Rumex violascens | violet dock | Polygonaceae | |
| Ruppia | widgeonweed | Ruppiaceae | |
| Ruppia cirrhosa | spiral ditchgrass | Ruppiaceae | |
| S | |||
| Saccharum | sugarcane | Poaceae | |
| Saccharum ravennae | ravennagrass | Poaceae | |
| Sageretia | mock buckthorn | Rhamnaceae | |
| Sageretia wrightii | Wright's mock buckthorn | Rhamnaceae | |
| Sagina | pearlwort | Caryophyllaceae | |
| Sagina decumbens | trailing pearlwort | Caryophyllaceae | |
| Sagina decumbens ssp. decumbens | trailing pearlwort | Caryophyllaceae | |
| Sagina decumbens ssp. occidentalis | western pearlwort | Caryophyllaceae | |
| Sagina saginoides | arctic pearlwort | Caryophyllaceae | |
| Sagittaria | arrowhead | Alismataceae | |
| Sagittaria calycina | hooded arrowhead | Alismataceae | |
| Sagittaria calycina var. calycina | hooded arrowhead | Alismataceae | |
| Sagittaria cuneata | arumleaf arrowhead | Alismataceae | |
| Sagittaria graminea | grassy arrowhead | Alismataceae | |
| Sagittaria graminea var. graminea | grassy arrowhead | Alismataceae | |
| Sagittaria latifolia | broadleaf arrowhead | Alismataceae | |
| Sagittaria longiloba | longbarb arrowhead | Alismataceae | |
| Sairocarpus | snapdragon | Scrophulariaceae | |
| Sairocarpus kingii | least snapdragon | Scrophulariaceae | |
| Sairocarpus nuttallianus | violet snapdragon | Scrophulariaceae | |
| Sairocarpus watsonii | Watson's snapdragon | Scrophulariaceae | |
| Salazaria | bladdersage | Lamiaceae | |
| Salazaria mexicana | Mexican bladdersage | Lamiaceae | |
| Salix | willow | Salicaceae | |
| Salix alba | white willow | Salicaceae | |
| Salix amygdaloides | peachleaf willow | Salicaceae | |
| Salix arizonica | Arizona willow | Salicaceae | |
| Salix bebbiana | Bebb willow | Salicaceae | |
| Salix bonplandiana | Bonpland willow | Salicaceae | |
| Salix boothii | Booth's willow | Salicaceae | |
| Salix exigua | narrowleaf willow | Salicaceae | |
| Salix geyeriana | Geyer willow | Salicaceae | |
| Salix gooddingii | Goodding's willow | Salicaceae | |
| Salix irrorata | dewystem willow | Salicaceae | |
| Salix laevigata | red willow | Salicaceae | |
| Salix lasiolepis | arroyo willow | Salicaceae | |
| Salix lasiolepis var. lasiolepis | arroyo willow | Salicaceae | |
| Salix ligulifolia | strapleaf willow | Salicaceae | |
| Salix lucida | shining willow | Salicaceae | |
| Salix lucida ssp. lasiandra | Pacific willow | Salicaceae | |
| Salix lutea | yellow willow | Salicaceae | |
| Salix monticola | park willow | Salicaceae | |
| Salix planifolia | diamondleaf willow | Salicaceae | |
| Salix planifolia ssp. planifolia | diamondleaf willow | Salicaceae | |
| Salix rubens | hybrid crack willow | Salicaceae | |
| Salix scouleriana | Scouler's willow | Salicaceae | |
| Salix sepulcralis | weeping willow | Salicaceae | |
| Salix taxifolia | yewleaf willow | Salicaceae | |
| Salpichroa | salpichroa | Solanaceae | |
| Salpichroa origanifolia | lily of the valley vine | Solanaceae | |
| Salsola | Russian thistle | Chenopodiaceae | |
| Salsola collina | slender Russian thistle | Chenopodiaceae | |
| Salsola paulsenii | barbwire Russian thistle | Chenopodiaceae | |
| Salsola tragus | prickly Russian thistle | Chenopodiaceae | |
| Salvia | sage | Lamiaceae | |
| Salvia aethiopis | Mediterranean sage | Lamiaceae | |
| Salvia amissa | Santa Catalina Mountain sage | Lamiaceae | |
| Salvia arizonica | desert indigo sage | Lamiaceae | |
| Salvia columbariae | chia | Lamiaceae | |
| Salvia columbariae var. columbariae | chia | Lamiaceae | |
| Salvia davidsonii | Davidson's sage | Lamiaceae | |
| Salvia dorrii | purple sage | Lamiaceae | |
| Salvia dorrii ssp. dorrii | purple sage | Lamiaceae | |
| Salvia dorrii ssp. dorrii var. dorrii | purple sage | Lamiaceae | |
| Salvia dorrii ssp. dorrii var. pilosa | purple sage | Lamiaceae | |
| Salvia dorrii ssp. mearnsii | purple sage | Lamiaceae | |
| Salvia henryi | crimson sage | Lamiaceae | |
| Salvia lemmonii | Lemmon's sage | Lamiaceae | |
| Salvia microphylla | baby sage | Lamiaceae | |
| Salvia mohavensis | Mojave sage | Lamiaceae | |
| Salvia pachyphylla | blue sage | Lamiaceae | |
| Salvia parryi | Parry's sage | Lamiaceae | |
| Salvia pinguifolia | rock sage | Lamiaceae | |
| Salvia reflexa | lanceleaf sage | Lamiaceae | |
| Salvia subincisa | sawtooth sage | Lamiaceae | |
| Salvia tiliifolia | lindenleaf sage | Lamiaceae | |
| Salvinia | watermoss | Salviniaceae | |
| Salvinia molesta | kariba-weed | Salviniaceae | |
| Sambucus | elderberry | Caprifoliaceae | |
| Sambucus nigra | black elderberry | Caprifoliaceae | |
| Sambucus nigra ssp. canadensis | American black elderberry | Caprifoliaceae | |
| Sambucus nigra ssp. cerulea | blue elderberry | Caprifoliaceae | |
| Sambucus racemosa | red elderberry | Caprifoliaceae | |
| Sambucus racemosa var. melanocarpa | Rocky Mountain elder | Caprifoliaceae | |
| Sambucus racemosa var. racemosa | red elderberry | Caprifoliaceae | |
| Samolus | brookweed | Primulaceae | |
| Samolus vagans | Chiricahua Mountain brookweed | Primulaceae | |
| Samolus valerandi | seaside brookweed | Primulaceae | |
| Samolus valerandi ssp. parviflorus | seaside brookweed | Primulaceae | |
| Sanguisorba | burnet | Rosaceae | |
| Sanguisorba annua | prairie burnet | Rosaceae | |
| Sanguisorba minor | small burnet | Rosaceae | |
| Sanguisorba minor ssp. balearica | small burnet | Rosaceae | |
| Sanvitalia | creeping zinnia | Asteraceae | |
| Sanvitalia abertii | Abert's creeping zinnia | Asteraceae | |
| Sapindus | soapberry | Sapindaceae | |
| Sapindus saponaria | wingleaf soapberry | Sapindaceae | |
| Sapindus saponaria var. drummondii | western soapberry | Sapindaceae | |
| Saponaria | soapwort | Caryophyllaceae | |
| Saponaria officinalis | bouncingbet | Caryophyllaceae | |
| Sarcobatus | greasewood | Chenopodiaceae | |
| Sarcobatus vermiculatus | greasewood | Chenopodiaceae | |
| Sarcocornia | swampfire | Chenopodiaceae | |
| Sarcocornia utahensis | Utah swampfire | Chenopodiaceae | |
| Saxifraga | saxifrage | Saxifragaceae | |
| Saxifraga caespitosa | tufted alpine saxifrage | Saxifragaceae | |
| Saxifraga caespitosa ssp. caespitosa | tufted alpine saxifrage | Saxifragaceae | |
| Saxifraga caespitosa ssp. monticola | tufted alpine saxifrage | Saxifragaceae | |
| Saxifraga eriophora | redfuzz saxifrage | Saxifragaceae | |
| Saxifraga flagellaris | whiplash saxifrage | Saxifragaceae | |
| Saxifraga flagellaris ssp. crandallii | Crandall's saxifrage | Saxifragaceae | |
| Saxifraga odontoloma | brook saxifrage | Saxifragaceae | |
| Saxifraga rhomboidea | diamondleaf saxifrage | Saxifragaceae | |
| Saxifraga rivularis | weak saxifrage | Saxifragaceae | |
| Scabrethia | Asteraceae | ||
| Scabrethia scabra | badlands mule-ears | Asteraceae | |
| Scabrethia scabra ssp. attenuata | badlands mule-ears | Asteraceae | |
| Scabrethia scabra ssp. canescens | badlands mule-ears | Asteraceae | |
| Scabrethia scabra ssp. scabra | badlands mule-ears | Asteraceae | |
| Scandix | scandix | Apiaceae | |
| Scandix pecten-veneris | shepherdsneedle | Apiaceae | |
| Schedonnardus | tumblegrass | Poaceae | |
| Schedonnardus paniculatus | tumblegrass | Poaceae | |
| Schedonorus | Poaceae | ||
| Schedonorus phoenix | tall fescue | Poaceae | |
| Schedonorus pratensis | meadow fescue | Poaceae | |
| Schiedeella | Orchidaceae | ||
| Schiedeella arizonica | parasitic lady's tresses | Orchidaceae | |
| Schismus | Mediterranean grass | Poaceae | |
| Schismus arabicus | Arabian schismus | Poaceae | |
| Schismus barbatus | common Mediterranean grass | Poaceae | |
| Schistophragma | schistophragma | Scrophulariaceae | |
| Schistophragma intermedia | harlequin spiralseed | Scrophulariaceae | |
| Schizachyrium | little bluestem | Poaceae | |
| Schizachyrium cirratum | Texas bluestem | Poaceae | |
| Schizachyrium sanguineum | crimson bluestem | Poaceae | |
| Schizachyrium sanguineum var. hirtiflorum | crimson bluestem | Poaceae | |
| Schizachyrium scoparium | little bluestem | Poaceae | |
| Schizachyrium scoparium var. scoparium | little bluestem | Poaceae | |
| Schkuhria | false threadleaf | Asteraceae | |
| Schkuhria anthemoidea | Wright's false threadleaf | Asteraceae | |
| Schkuhria anthemoidea var. wrightii | Wright's false threadleaf | Asteraceae | |
| Schkuhria multiflora | manyflower false threadleaf | Asteraceae | |
| Schkuhria pinnata | pinnate false threadleaf | Asteraceae | |
| Schkuhria pinnata var. guatemalensis | Wislizenus' false threadleaf | Asteraceae | |
| Schoenocrambe | plainsmustard | Brassicaceae | |
| Schoenocrambe linearifolia | slimleaf plainsmustard | Brassicaceae | |
| Schoenoplectus | bulrush | Cyperaceae | |
| Schoenoplectus acutus | hardstem bulrush | Cyperaceae | |
| Schoenoplectus acutus var. occidentalis | tule | Cyperaceae | |
| Schoenoplectus americanus | chairmaker's bulrush | Cyperaceae | |
| Schoenoplectus californicus | California bulrush | Cyperaceae | |
| Schoenoplectus fluviatilis | river bulrush | Cyperaceae | |
| Schoenoplectus maritimus | cosmopolitan bulrush | Cyperaceae | |
| Schoenoplectus pungens | common threesquare | Cyperaceae | |
| Schoenoplectus pungens var. longispicatus | common threesquare | Cyperaceae | |
| Schoenoplectus tabernaemontani | softstem bulrush | Cyperaceae | |
| Scirpus | bulrush | Cyperaceae | |
| Scirpus atrovirens | green bulrush | Cyperaceae | |
| Scirpus microcarpus | panicled bulrush | Cyperaceae | |
| Scirpus pallidus | cloaked bulrush | Cyperaceae | |
| Scirpus pendulus | rufous bulrush | Cyperaceae | |
| Sclerocactus | fishhook cactus | Cactaceae | |
| Sclerocactus papyracanthus | paperspine fishhook cactus | Cactaceae | |
| Sclerocactus parviflorus | smallflower fishhook cactus | Cactaceae | |
| Sclerocactus parviflorus ssp. havasupaiensis | Cactaceae | ||
| Sclerocactus parviflorus ssp. intermedius | intermediate fishhook cactus | Cactaceae | |
| Sclerocactus parviflorus ssp. parviflorus | smallflower fishhook cactus | Cactaceae | |
| Sclerocactus parviflorus ssp. terrae-canyonae | longspine fishhook cactus | Cactaceae | |
| Sclerocactus sileri | Siler's pincushion cactus | Cactaceae | |
| Sclerocactus whipplei | Whipple's fishhook cactus | Cactaceae | |
| Sclerochloa | hardgrass | Poaceae | |
| Sclerochloa dura | common hardgrass | Poaceae | |
| Scleropogon | burrograss | Poaceae | |
| Scleropogon brevifolius | burrograss | Poaceae | |
| Scrophularia | figwort | Scrophulariaceae | |
| Scrophularia parviflora | pineland figwort | Scrophulariaceae | |
| Scutellaria | skullcap | Lamiaceae | |
| Scutellaria drummondii | Drummond's skullcap | Lamiaceae | |
| Scutellaria drummondii var. edwardsiana | Drummond's skullcap | Lamiaceae | |
| Scutellaria galericulata | marsh skullcap | Lamiaceae | |
| Scutellaria lateriflora | blue skullcap | Lamiaceae | |
| Scutellaria lateriflora var. lateriflora | blue skullcap | Lamiaceae | |
| Scutellaria potosina | Mexican skullcap | Lamiaceae | |
| Scutellaria potosina ssp. platyphylla | Mexican skullcap | Lamiaceae | |
| Scutellaria potosina ssp. platyphylla var. platyphylla | Mexican skullcap | Lamiaceae | |
| Scutellaria potosina ssp. potosina | Mexican skullcap | Lamiaceae | |
| Scutellaria potosina ssp. potosina var. grahamiana | Mexican skullcap | Lamiaceae | |
| Scutellaria potosina ssp. potosina var. tessellata | Mexican skullcap | Lamiaceae | |
| Sebastiania | Sebastian-bush | Euphorbiaceae | |
| Sebastiania bilocularis | arrow poision plant | Euphorbiaceae | |
| Secale | rye | Poaceae | |
| Secale cereale | cereal rye | Poaceae | |
| Securigera | Fabaceae | ||
| Securigera varia | crownvetch | Fabaceae | |
| Sedum | stonecrop | Crassulaceae | |
| Sedum cockerellii | Cockerell's stonecrop | Crassulaceae | |
| Sedum lanceolatum | spearleaf stonecrop | Crassulaceae | |
| Sedum lanceolatum ssp. lanceolatum | spearleaf stonecrop | Crassulaceae | |
| Sedum stelliforme | Huachuca Mountain stonecrop | Crassulaceae | |
| Selaginella | spikemoss | Selaginellaceae | |
| Selaginella arizonica | Arizona spikemoss | Selaginellaceae | |
| Selaginella densa | lesser spikemoss | Selaginellaceae | |
| Selaginella densa var. densa | lesser spikemoss | Selaginellaceae | |
| Selaginella densa var. scopulorum | Rocky Mountain spikemoss | Selaginellaceae | |
| Selaginella eremophila | desert spikemoss | Selaginellaceae | |
| Selaginella leucobryoides | Mojave spikemoss | Selaginellaceae | |
| Selaginella mutica | bluntleaf spikemoss | Selaginellaceae | |
| Selaginella mutica var. limitanea | bluntleaf spikemoss | Selaginellaceae | |
| Selaginella mutica var. mutica | bluntleaf spikemoss | Selaginellaceae | |
| Selaginella neomexicana | Selaginellaceae | ||
| Selaginella rupincola | rockloving spikemoss | Selaginellaceae | |
| Selaginella underwoodii | Underwood's spikemoss | Selaginellaceae | |
| Selaginella watsonii | Watson's spikemoss | Selaginellaceae | |
| Selinocarpus | moonpod | Nyctaginaceae | |
| Selinocarpus nevadensis | desert moonpod | Nyctaginaceae | |
| Senecio | ragwort | Asteraceae | |
| Senecio actinella | Flagstaff ragwort | Asteraceae | |
| Senecio arizonicus | Arizona ragwort | Asteraceae | |
| Senecio bigelovii | nodding ragwort | Asteraceae | |
| Senecio bigelovii var. bigelovii | nodding ragwort | Asteraceae | |
| Senecio bigelovii var. hallii | Hall's ragwort | Asteraceae | |
| Senecio eremophilus | desert ragwort | Asteraceae | |
| Senecio eremophilus var. kingii | King's ragwort | Asteraceae | |
| Senecio eremophilus var. macdougalii | MacDougal's ragwort | Asteraceae | |
| Senecio flaccidus | threadleaf ragwort | Asteraceae | |
| Senecio flaccidus var. flaccidus | threadleaf ragwort | Asteraceae | |
| Senecio flaccidus var. monoensis | smooth threadleaf ragwort | Asteraceae | |
| Senecio lemmonii | Lemmon's ragwort | Asteraceae | |
| Senecio mohavensis | Mojave ragwort | Asteraceae | |
| Senecio multidentatus | Huachuca Mountain ragwort | Asteraceae | |
| Senecio multidentatus var. huachucanus | Huachuca Mountain ragwort | Asteraceae | |
| Senecio parryi | mountain ragwort | Asteraceae | |
| Senecio riddellii | Riddell's ragwort | Asteraceae | |
| Senecio spartioides | broom-like ragwort | Asteraceae | |
| Senecio spartioides var. multicapitatus | broom-like ragwort | Asteraceae | |
| Senecio spartioides var. spartioides | broom-like ragwort | Asteraceae | |
| Senecio vulgaris | old-man-in-the-Spring | Asteraceae | |
| Senecio wootonii | Wooton's ragwort | Asteraceae | |
| Senna | senna | Fabaceae | |
| Senna armata | desertsenna | Fabaceae | |
| Senna artemisioides | silver senna | Fabaceae | |
| Senna bauhinioides | twinleaf senna | Fabaceae | |
| Senna covesii | Coues' cassia | Fabaceae | |
| Senna didymobotrya | African senna | Fabaceae | |
| Senna hirsuta | woolly senna | Fabaceae | |
| Senna hirsuta var. glaberrima | woolly senna | Fabaceae | |
| Senna lindheimeriana | velvet leaf senna | Fabaceae | |
| Senna pendula | valamuerto | Fabaceae | |
| Senna pendula var. glabrata | valamuerto | Fabaceae | |
| Senna wislizeni | Wislizenus' senna | Fabaceae | |
| Sesbania | riverhemp | Fabaceae | |
| Sesbania herbacea | bigpod sesbania | Fabaceae | |
| Sesuvium | seapurslane | Aizoaceae | |
| Sesuvium verrucosum | verrucose seapurslane | Aizoaceae | |
| Setaria | bristlegrass | Poaceae | |
| Setaria adhaerens | bur bristlegrass | Poaceae | |
| Setaria arizonica | Arizona bristlegrass | Poaceae | |
| Setaria faberi | Japanese bristlegrass | Poaceae | |
| Setaria grisebachii | Grisebach's bristlegrass | Poaceae | |
| Setaria italica | foxtail bristlegrass | Poaceae | |
| Setaria leucopila | streambed bristlegrass | Poaceae | |
| Setaria liebmannii | Liebmann's bristlegrass | Poaceae | |
| Setaria macrostachya | large-spike bristlegrass | Poaceae | |
| Setaria parviflora | marsh bristlegrass | Poaceae | |
| Setaria pumila | yellow foxtail | Poaceae | |
| Setaria pumila ssp. pumila | yellow foxtail | Poaceae | |
| Setaria scheelei | southwestern bristlegrass | Poaceae | |
| Setaria verticillata | hooked bristlegrass | Poaceae | |
| Setaria villosissima | hairyleaf bristlegrass | Poaceae | |
| Setaria viridis | green bristlegrass | Poaceae | |
| Setaria viridis var. viridis | green bristlegrass | Poaceae | |
| Setaria vulpiseta | plains bristlegrass | Poaceae | |
| Setariopsis | Poaceae | ||
| Setariopsis auriculata | Poaceae | ||
| Seymeria | blacksenna | Scrophulariaceae | |
| Seymeria bipinnatisecta | Eagle Pass blacksenna | Scrophulariaceae | |
| Shepherdia | buffaloberry | Elaeagnaceae | |
| Shepherdia argentea | silver buffaloberry | Elaeagnaceae | |
| Shepherdia canadensis | russet buffaloberry | Elaeagnaceae | |
| Shepherdia rotundifolia | roundleaf buffaloberry | Elaeagnaceae | |
| Sherardia | sherardia | Rubiaceae | |
| Sherardia arvensis | blue fieldmadder | Rubiaceae | |
| Sibbaldia | sibbaldia | Rosaceae | |
| Sibbaldia procumbens | creeping sibbaldia | Rosaceae | |
| Sicyos | bur cucumber | Cucurbitaceae | |
| Sicyos ampelophyllus | streamside bur cucumber | Cucurbitaceae | |
| Sicyos laciniatus | cutleaf bur cucumber | Cucurbitaceae | |
| Sicyosperma | sicyosperma | Cucurbitaceae | |
| Sicyosperma gracile | climbing arrowheads | Cucurbitaceae | |
| Sida | fanpetals | Malvaceae | |
| Sida abutifolia | spreading fanpetals | Malvaceae | |
| Sida neomexicana | New Mexico fanpetals | Malvaceae | |
| Sida rhombifolia | Cuban jute | Malvaceae | |
| Sida spinosa | prickly fanpetals | Malvaceae | |
| Sida tragiifolia | earleaf fanpetals | Malvaceae | |
| Sidalcea | checkerbloom | Malvaceae | |
| Sidalcea neomexicana | salt spring checkerbloom | Malvaceae | |
| Sidalcea neomexicana ssp. neomexicana | salt spring checkerbloom | Malvaceae | |
| Sidalcea neomexicana ssp. thurberi | Thurber's checkerbloom | Malvaceae | |
| Sideroxylon | bully | Sapotaceae | |
| Sideroxylon lanuginosum | gum bully | Sapotaceae | |
| Sideroxylon lanuginosum ssp. rigidum | gum bully | Sapotaceae | |
| Silene | catchfly | Caryophyllaceae | |
| Silene acaulis | moss campion | Caryophyllaceae | |
| Silene acaulis var. subacaulescens | moss campion | Caryophyllaceae | |
| Silene antirrhina | sleepy silene | Caryophyllaceae | |
| Silene drummondii | Drummond's campion | Caryophyllaceae | |
| Silene drummondii var. drummondii | Drummond's campion | Caryophyllaceae | |
| Silene gallica | common catchfly | Caryophyllaceae | |
| Silene laciniata | cardinal catchfly | Caryophyllaceae | |
| Silene laciniata ssp. greggii | cardinal catchfly | Caryophyllaceae | |
| Silene menziesii | Menzies' campion | Caryophyllaceae | |
| Silene menziesii ssp. menziesii | Menzies' campion | Caryophyllaceae | |
| Silene menziesii ssp. menziesii var. menziesii | Menzies' campion | Caryophyllaceae | |
| Silene rectiramea | Grand Canyon campion | Caryophyllaceae | |
| Silene scouleri | simple campion | Caryophyllaceae | |
| Silene scouleri ssp. pringlei | simple campion | Caryophyllaceae | |
| Silene scouleri ssp. pringlei var. concolor | simple campion | Caryophyllaceae | |
| Silene scouleri ssp. pringlei var. eglandulosa | simple campion | Caryophyllaceae | |
| Silene scouleri ssp. pringlei var. leptophylla | simple campion | Caryophyllaceae | |
| Silene scouleri ssp. pringlei var. pringlei | simple campion | Caryophyllaceae | |
| Silene thurberi | woolly catchfly | Caryophyllaceae | |
| Silybum | milkthistle | Asteraceae | |
| Silybum marianum | blessed milkthistle | Asteraceae | |
| Simmondsia | goatnut | Simmondsiaceae | |
| Simmondsia chinensis | jojoba | Simmondsiaceae | |
| Simsia | bushsunflower | Asteraceae | |
| Simsia lagasceiformis | annual bushsunflower | Asteraceae | |
| Sinapis | mustard | Brassicaceae | |
| Sinapis alba | white mustard | Brassicaceae | |
| Sinapis arvensis | charlock mustard | Brassicaceae | |
| Sinapis arvensis ssp. arvensis | wild mustard | Brassicaceae | |
| Sisymbrium | hedgemustard | Brassicaceae | |
| Sisymbrium altissimum | tall tumblemustard | Brassicaceae | |
| Sisymbrium irio | London rocket | Brassicaceae | |
| Sisymbrium orientale | Indian hedgemustard | Brassicaceae | |
| Sisyrinchium | blue-eyed grass | Iridaceae | |
| Sisyrinchium arizonicum | Arizona blue-eyed grass | Iridaceae | |
| Sisyrinchium cernuum | nodding blue-eyed grass | Iridaceae | |
| Sisyrinchium demissum | stiff blue-eyed grass | Iridaceae | |
| Sisyrinchium idahoense | Idaho blue-eyed grass | Iridaceae | |
| Sisyrinchium idahoense var. occidentale | Idaho blue-eyed grass | Iridaceae | |
| Sisyrinchium longipes | timberland blue-eyed grass | Iridaceae | |
| Sisyrinchium macrocarpon | Willow Spring blue-eyed grass | Iridaceae | |
| Sium | waterparsnip | Apiaceae | |
| Sium suave | hemlock waterparsnip | Apiaceae | |
| Solanum | nightshade | Solanaceae | |
| Solanum adscendens | sonoita nightshade | Solanaceae | |
| Solanum americanum | American black nightshade | Solanaceae | |
| Solanum carolinense | Carolina horsenettle | Solanaceae | |
| Solanum carolinense var. carolinense | Carolina horsenettle | Solanaceae | |
| Solanum douglasii | greenspot nightshade | Solanaceae | |
| Solanum elaeagnifolium | silverleaf nightshade | Solanaceae | |
| Solanum fendleri | Fendler's horsenettle | Solanaceae | |
| Solanum fendleri var. fendleri | Fendler's horsenettle | Solanaceae | |
| Solanum heterodoxum | melonleaf nightshade | Solanaceae | |
| Solanum heterodoxum var. setigeroides | melonleaf nightshade | Solanaceae | |
| Solanum hindsianum | Hinds' nightshade | Solanaceae | |
| Solanum jamesii | wild potato | Solanaceae | |
| Solanum lumholtzianum | Sonoran nightshade | Solanaceae | |
| Solanum lycopersicum | garden tomato | Solanaceae | |
| Solanum lycopersicum var. lycopersicum | garden tomato | Solanaceae | |
| Solanum physalifolium | hoe nightshade | Solanaceae | |
| Solanum pinnatisectum | tansyleaf nightshade | Solanaceae | |
| Solanum ptycanthum | West Indian nightshade | Solanaceae | |
| Solanum rostratum | buffalobur nightshade | Solanaceae | |
| Solanum sisymbriifolium | sticky nightshade | Solanaceae | |
| Solanum triflorum | cutleaf nightshade | Solanaceae | |
| Solanum umbelliferum | bluewitch nightshade | Solanaceae | |
| Solanum umbelliferum var. glabrescens | bluewitch | Solanaceae | |
| Solanum xanti | chaparral nightshade | Solanaceae | |
| Solanum xanti var. xanti | chaparral nightshade | Solanaceae | |
| Solidago | goldenrod | Asteraceae | |
| Solidago altissima | Canada goldenrod | Asteraceae | |
| Solidago canadensis | Canada goldenrod | Asteraceae | |
| Solidago canadensis var. gilvocanescens | shorthair goldenrod | Asteraceae | |
| Solidago missouriensis | Missouri goldenrod | Asteraceae | |
| Solidago missouriensis var. fasciculata | Missouri goldenrod | Asteraceae | |
| Solidago missouriensis var. missouriensis | Missouri goldenrod | Asteraceae | |
| Solidago missouriensis var. tenuissima | Missouri goldenrod | Asteraceae | |
| Solidago multiradiata | Rocky Mountain goldenrod | Asteraceae | |
| Solidago multiradiata var. scopulorum | manyray goldenrod | Asteraceae | |
| Solidago nana | baby goldenrod | Asteraceae | |
| Solidago simplex | Mt. Albert goldenrod | Asteraceae | |
| Solidago simplex ssp. simplex | Mt. Albert goldenrod | Asteraceae | |
| Solidago simplex ssp. simplex var. simplex | Mt. Albert goldenrod | Asteraceae | |
| Solidago spectabilis | Nevada goldenrod | Asteraceae | |
| Solidago spectabilis var. spectabilis | Nevada goldenrod | Asteraceae | |
| Solidago velutina | threenerve goldenrod | Asteraceae | |
| Solidago wrightii | Wright's goldenrod | Asteraceae | |
| Solidago wrightii var. adenophora | Wright's goldenrod | Asteraceae | |
| Solidago wrightii var. wrightii | Wright's goldenrod | Asteraceae | |
| Soliva | burrweed | Asteraceae | |
| Soliva sessilis | field burrweed | Asteraceae | |
| Sonchus | sowthistle | Asteraceae | |
| Sonchus asper | spiny sowthistle | Asteraceae | |
| Sonchus oleraceus | common sowthistle | Asteraceae | |
| Sophora | necklacepod | Fabaceae | |
| Sophora arizonica | Arizona necklacepod | Fabaceae | |
| Sophora nuttalliana | silky sophora | Fabaceae | |
| Sophora stenophylla | fringeleaf necklacepod | Fabaceae | |
| Sorbus | mountain ash | Rosaceae | |
| Sorbus dumosa | Arizona mountain ash | Rosaceae | |
| Sorbus scopulina | Greene's mountain ash | Rosaceae | |
| Sorbus scopulina var. scopulina | Greene's mountain ash | Rosaceae | |
| Sorghastrum | Indiangrass | Poaceae | |
| Sorghastrum nutans | Indiangrass | Poaceae | |
| Sorghum | sorghum | Poaceae | |
| Sorghum bicolor | sorghum | Poaceae | |
| Sorghum bicolor ssp. bicolor | grain sorghum | Poaceae | |
| Sorghum bicolor ssp. drummondii | Sudangrass | Poaceae | |
| Sorghum halepense | Johnsongrass | Poaceae | |
| Sparganium | bur-reed | Sparganiaceae | |
| Sparganium angustifolium | narrowleaf bur-reed | Sparganiaceae | |
| Sparganium emersum | European bur-reed | Sparganiaceae | |
| Sparganium eurycarpum | broadfruit bur-reed | Sparganiaceae | |
| Sparganium natans | small bur-reed | Sparganiaceae | |
| Spartina | cordgrass | Poaceae | |
| Spartina gracilis | alkali cordgrass | Poaceae | |
| Spergularia | sandspurry | Caryophyllaceae | |
| Spergularia salina | salt sandspurry | Caryophyllaceae | |
| Spermolepis | scaleseed | Apiaceae | |
| Spermolepis echinata | bristly scaleseed | Apiaceae | |
| Sphaeralcea | globemallow | Malvaceae | |
| Sphaeralcea ambigua | desert globemallow | Malvaceae | |
| Sphaeralcea ambigua ssp. ambigua | apricot globemallow | Malvaceae | |
| Sphaeralcea ambigua ssp. rosacea | rose globemallow | Malvaceae | |
| Sphaeralcea angustifolia | copper globemallow | Malvaceae | |
| Sphaeralcea coccinea | scarlet globemallow | Malvaceae | |
| Sphaeralcea coccinea ssp. coccinea | scarlet globemallow | Malvaceae | |
| Sphaeralcea coccinea ssp. elata | scarlet globemallow | Malvaceae | |
| Sphaeralcea coulteri | Coulter's globemallow | Malvaceae | |
| Sphaeralcea digitata | juniper globemallow | Malvaceae | |
| Sphaeralcea digitata ssp. digitata | juniper globemallow | Malvaceae | |
| Sphaeralcea emoryi | Emory's globemallow | Malvaceae | |
| Sphaeralcea fendleri | Fendler's globemallow | Malvaceae | |
| Sphaeralcea fendleri ssp. albescens | thicket globemallow | Malvaceae | |
| Sphaeralcea fendleri ssp. elongata | thicket globemallow | Malvaceae | |
| Sphaeralcea fendleri ssp. fendleri | Fendler's globemallow | Malvaceae | |
| Sphaeralcea fendleri ssp. tripartita | thicket globemallow | Malvaceae | |
| Sphaeralcea fendleri ssp. venusta | thicket globemallow | Malvaceae | |
| Sphaeralcea grossulariifolia | gooseberryleaf globemallow | Malvaceae | |
| Sphaeralcea grossulariifolia ssp. grossulariifolia | gooseberryleaf globemallow | Malvaceae | |
| Sphaeralcea grossulariifolia ssp. pedata | gooseberryleaf globemallow | Malvaceae | |
| Sphaeralcea hastulata | spear globemallow | Malvaceae | |
| Sphaeralcea incana | gray globemallow | Malvaceae | |
| Sphaeralcea incana ssp. cuneata | soft globemallow | Malvaceae | |
| Sphaeralcea incana ssp. incana | gray globemallow | Malvaceae | |
| Sphaeralcea laxa | caliche globemallow | Malvaceae | |
| Sphaeralcea leptophylla | scaly globemallow | Malvaceae | |
| Sphaeralcea orcuttii | Carrizo Creek globemallow | Malvaceae | |
| Sphaeralcea parvifolia | smallflower globemallow | Malvaceae | |
| Sphaeralcea rusbyi | Rusby's globemallow | Malvaceae | |
| Sphaeralcea rusbyi ssp. gilensis | Gila globemallow | Malvaceae | |
| Sphaeralcea rusbyi ssp. rusbyi | Rusby's globemallow | Malvaceae | |
| Sphaeralcea wrightii | Wright's globemallow | Malvaceae | |
| Sphaerophysa | sphaerophysa | Fabaceae | |
| Sphaerophysa salsula | alkali swainsonpea | Fabaceae | |
| Sphenopholis | wedgescale | Poaceae | |
| Sphenopholis intermedia | slender wedgescale | Poaceae | |
| Sphenopholis obtusata | prairie wedgescale | Poaceae | |
| Sphinctospermum | sphinctospermum | Fabaceae | |
| Sphinctospermum constrictum | hourglass peaseed | Fabaceae | |
| Spiranthes | lady's tresses | Orchidaceae | |
| Spiranthes delitescens | reclusive lady's tresses | Orchidaceae | |
| Spiranthes romanzoffiana | hooded lady's tresses | Orchidaceae | |
| Spirodela | duckmeat | Lemnaceae | |
| Spirodela polyrrhiza | common duckmeat | Lemnaceae | |
| Sporobolus | dropseed | Poaceae | |
| Sporobolus airoides | alkali sacaton | Poaceae | |
| Sporobolus compositus | composite dropseed | Poaceae | |
| Sporobolus compositus var. compositus | composite dropseed | Poaceae | |
| Sporobolus contractus | spike dropseed | Poaceae | |
| Sporobolus cryptandrus | sand dropseed | Poaceae | |
| Sporobolus domingensis | coral dropseed | Poaceae | |
| Sporobolus flexuosus | mesa dropseed | Poaceae | |
| Sporobolus giganteus | giant dropseed | Poaceae | |
| Sporobolus interruptus | black dropseed | Poaceae | |
| Sporobolus junceus | pineywoods dropseed | Poaceae | |
| Sporobolus nealleyi | gyp dropseed | Poaceae | |
| Sporobolus neglectus | puffsheath dropseed | Poaceae | |
| Sporobolus pyramidatus | Madagascar dropseed | Poaceae | |
| Sporobolus texanus | Texas dropseed | Poaceae | |
| Sporobolus vaginiflorus | poverty dropseed | Poaceae | |
| Sporobolus vaginiflorus var. vaginiflorus | poverty dropseed | Poaceae | |
| Sporobolus wrightii | big sacaton | Poaceae | |
| Stachys | hedgenettle | Lamiaceae | |
| Stachys coccinea | scarlet hedgenettle | Lamiaceae | |
| Stachys crenata | mousesear | Lamiaceae | |
| Stachys pilosa | hairy hedgenettle | Lamiaceae | |
| Stachys pilosa var. pilosa | hairy hedgenettle | Lamiaceae | |
| Stachys rothrockii | Rothrock's hedgenettle | Lamiaceae | |
| Stanleya | princesplume | Brassicaceae | |
| Stanleya albescens | white princesplume | Brassicaceae | |
| Stanleya pinnata | desert princesplume | Brassicaceae | |
| Stanleya pinnata var. pinnata | desert princesplume | Brassicaceae | |
| Stellaria | starwort | Caryophyllaceae | |
| Stellaria longifolia | longleaf starwort | Caryophyllaceae | |
| Stellaria longifolia var. longifolia | longleaf starwort | Caryophyllaceae | |
| Stellaria longipes | longstalk starwort | Caryophyllaceae | |
| Stellaria longipes ssp. longipes | chickweed, starwort | Caryophyllaceae | |
| Stellaria media | common chickweed | Caryophyllaceae | |
| Stellaria media ssp. media | common chickweed | Caryophyllaceae | |
| Stellaria nitens | shiny chickweed | Caryophyllaceae | |
| Stellaria porsildii | Porsild's starwort | Caryophyllaceae | |
| Stellaria umbellata | umbrella starwort | Caryophyllaceae | |
| Stemodia | twintip | Scrophulariaceae | |
| Stemodia durantifolia | whitewoolly twintip | Scrophulariaceae | |
| Stenocereus | stenocereus | Cactaceae | |
| Stenocereus thurberi | organpipe cactus | Cactaceae | |
| Stenogonum | buckwheat | Polygonaceae | |
| Stenogonum flexum | bent two-whorl buckwheat | Polygonaceae | |
| Stenogonum salsuginosum | salty buckwheat | Polygonaceae | |
| Stenorrhynchos | lady orchid | Orchidaceae | |
| Stenorrhynchos michuacanum | Michuacan lady orchid | Orchidaceae | |
| Stenotus | mock goldenweed | Asteraceae | |
| Stenotus acaulis | stemless mock goldenweed | Asteraceae | |
| Stenotus armerioides | thrift mock goldenweed | Asteraceae | |
| Stenotus armerioides var. armerioides | thrift mock goldenweed | Asteraceae | |
| Stephanomeria | wirelettuce | Asteraceae | |
| Stephanomeria exigua | small wirelettuce | Asteraceae | |
| Stephanomeria exigua ssp. exigua | small wirelettuce | Asteraceae | |
| Stephanomeria minor | lesser wirelettuce | Asteraceae | |
| Stephanomeria minor var. minor | narrowleaf wirelettuce | Asteraceae | |
| Stephanomeria parryi | Parry's wirelettuce | Asteraceae | |
| Stephanomeria pauciflora | brownplume wirelettuce | Asteraceae | |
| Stephanomeria schottii | Schott's wirelettuce | Asteraceae | |
| Stephanomeria thurberi | Thurber's wirelettuce | Asteraceae | |
| Stevia | candyleaf | Asteraceae | |
| Stevia lemmonii | Lemmon's candyleaf | Asteraceae | |
| Stevia micrantha | annual candyleaf | Asteraceae | |
| Stevia plummerae | Plummer's candyleaf | Asteraceae | |
| Stevia plummerae var. alba | Plummer's candyleaf | Asteraceae | |
| Stevia plummerae var. plummerae | Plummer's candyleaf | Asteraceae | |
| Stevia serrata | sawtooth candyleaf | Asteraceae | |
| Stevia viscida | viscid candyleaf | Asteraceae | |
| Stillingia | toothleaf | Euphorbiaceae | |
| Stillingia linearifolia | queen's-root | Euphorbiaceae | |
| Stillingia paucidentata | Mojave toothleaf | Euphorbiaceae | |
| Stillingia spinulosa | annual toothleaf | Euphorbiaceae | |
| Streptanthella | streptanthella | Brassicaceae | |
| Streptanthella longirostris | longbeak streptanthella | Brassicaceae | |
| Streptanthus | twistflower | Brassicaceae | |
| Streptanthus carinatus | lyreleaf jewelflower | Brassicaceae | |
| Streptanthus carinatus ssp. arizonicus | lyreleaf jewelflower | Brassicaceae | |
| Streptanthus carinatus ssp. carinatus | lyreleaf jewelflower | Brassicaceae | |
| Streptanthus cordatus | heartleaf twistflower | Brassicaceae | |
| Streptanthus cordatus var. cordatus | heartleaf twistflower | Brassicaceae | |
| Streptanthus lemmonii | Lemmon's jewelflower | Brassicaceae | |
| Streptopus | twistedstalk | Liliaceae | |
| Streptopus amplexifolius | claspleaf twistedstalk | Liliaceae | |
| Streptopus amplexifolius var. amplexifolius | claspleaf twistedstalk | Liliaceae | |
| Strophostyles | fuzzybean | Fabaceae | |
| Strophostyles leiosperma | slickseed fuzzybean | Fabaceae | |
| Stuckenia | pondweed | Potamogetonaceae | |
| Stuckenia filiformis | fineleaf pondweed | Potamogetonaceae | |
| Stuckenia filiformis ssp. alpina | fineleaf pondweed | Potamogetonaceae | |
| Stuckenia pectinata | sago pondweed | Potamogetonaceae | |
| Stuckenia striata | broadleaf pondweed | Potamogetonaceae | |
| Stylocline | neststraw | Asteraceae | |
| Stylocline gnaphalioides | mountain neststraw | Asteraceae | |
| Stylocline intertexta | Morefield's neststraw | Asteraceae | |
| Stylocline micropoides | woollyhead neststraw | Asteraceae | |
| Stylocline sonorensis | Sonoran neststraw | Asteraceae | |
| Stylosanthes | pencilflower | Fabaceae | |
| Stylosanthes biflora | sidebeak pencilflower | Fabaceae | |
| Stylosanthes humilis | Townsville stylo | Fabaceae | |
| Suaeda | seepweed | Chenopodiaceae | |
| Suaeda calceoliformis | Pursh seepweed | Chenopodiaceae | |
| Suaeda moquinii | Mojave seablite | Chenopodiaceae | |
| Suaeda suffrutescens | desert seepweed | Chenopodiaceae | |
| Suaeda suffrutescens var. suffrutescens | desert seepweed | Chenopodiaceae | |
| Swertia | felwort | Gentianaceae | |
| Swertia perennis | felwort | Gentianaceae | |
| Symphoricarpos | snowberry | Caprifoliaceae | |
| Symphoricarpos longiflorus | desert snowberry | Caprifoliaceae | |
| Symphoricarpos oreophilus | mountain snowberry | Caprifoliaceae | |
| Symphoricarpos oreophilus var. oreophilus | mountain snowberry | Caprifoliaceae | |
| Symphoricarpos oreophilus var. utahensis | Utah snowberry | Caprifoliaceae | |
| Symphoricarpos palmeri | Palmer's snowberry | Caprifoliaceae | |
| Symphoricarpos rotundifolius | roundleaf snowberry | Caprifoliaceae | |
| Symphoricarpos rotundifolius var. parishii | Parish's snowberry | Caprifoliaceae | |
| Symphyotrichum | aster | Asteraceae | |
| Symphyotrichum ascendens | western aster | Asteraceae | |
| Symphyotrichum eatonii | Eaton's aster | Asteraceae | |
| Symphyotrichum ericoides | white heath aster | Asteraceae | |
| Symphyotrichum ericoides var. ericoides | white heath aster | Asteraceae | |
| Symphyotrichum expansum | southwestern annual saltmarsh aster | Asteraceae | |
| Symphyotrichum falcatum | white prairie aster | Asteraceae | |
| Symphyotrichum falcatum var. commutatum | white prairie aster | Asteraceae | |
| Symphyotrichum falcatum var. falcatum | white prairie aster | Asteraceae | |
| Symphyotrichum foliaceum | alpine leafybract aster | Asteraceae | |
| Symphyotrichum foliaceum var. canbyi | Canby's aster | Asteraceae | |
| Symphyotrichum foliaceum var. parryi | Parry's aster | Asteraceae | |
| Symphyotrichum frondosum | short-rayed alkali aster | Asteraceae | |
| Symphyotrichum laeve | smooth blue aster | Asteraceae | |
| Symphyotrichum laeve var. geyeri | Geyer's aster | Asteraceae | |
| Symphyotrichum lanceolatum | white panicle aster | Asteraceae | |
| Symphyotrichum lanceolatum ssp. hesperium | white panicle aster | Asteraceae | |
| Symphyotrichum lanceolatum ssp. hesperium var. hesperium | white panicle aster | Asteraceae | |
| Symphyotrichum potosinum | Santa Rita Mountain aster | Asteraceae | |
| Syntrichopappus | Fremont's-gold | Asteraceae | |
| Syntrichopappus fremontii | yellowray Fremont's-gold | Asteraceae | |
| T | |||
| Tagetes | marigold | Asteraceae | |
| Tagetes lemmonii | Lemmon's marigold | Asteraceae | |
| Tagetes micrantha | licorice marigold | Asteraceae | |
| Talinum | fameflower | Portulacaceae | |
| Talinum gooddingii | Goodding's fameflower | Portulacaceae | |
| Talinum paniculatum | jewels of Opar | Portulacaceae | |
| Tamarix | tamarisk | Tamaricaceae | |
| Tamarix africana | African tamarisk | Tamaricaceae | |
| Tamarix aphylla | Athel tamarisk | Tamaricaceae | |
| Tamarix canariensis | Canary Island tamarisk | Tamaricaceae | |
| Tamarix chinensis | five-stamen tamarisk | Tamaricaceae | |
| Tamarix parviflora | smallflower tamarisk | Tamaricaceae | |
| Tamarix ramosissima | saltcedar | Tamaricaceae | |
| Tanacetum | tansy | Asteraceae | |
| Tanacetum vulgare | common tansy | Asteraceae | |
| Taraxacum | dandelion | Asteraceae | |
| Taraxacum laevigatum | rock dandelion | Asteraceae | |
| Taraxacum lyratum | harp dandelion | Asteraceae | |
| Taraxacum officinale | common dandelion | Asteraceae | |
| Taraxacum officinale ssp. officinale | common dandelion | Asteraceae | |
| Tecoma | trumpetbush | Bignoniaceae | |
| Tecoma stans | yellow trumpetbush | Bignoniaceae | |
| Tephrosia | hoarypea | Fabaceae | |
| Tephrosia leiocarpa | smoothpod hoarypea | Fabaceae | |
| Tephrosia thurberi | Thurber's hoarypea | Fabaceae | |
| Tephrosia vicioides | red hoarypea | Fabaceae | |
| Tetraclea | tetraclea | Verbenaceae | |
| Tetraclea coulteri | Coulter's wrinklefruit | Verbenaceae | |
| Tetracoccus | shrubby-spurge | Euphorbiaceae | |
| Tetracoccus hallii | Hall's shrubby-spurge | Euphorbiaceae | |
| Tetradymia | horsebrush | Asteraceae | |
| Tetradymia argyraea | striped cottonthorn | Asteraceae | |
| Tetradymia axillaris | longspine horsebrush | Asteraceae | |
| Tetradymia axillaris var. longispina | longspine horsebrush | Asteraceae | |
| Tetradymia canescens | spineless horsebrush | Asteraceae | |
| Tetradymia stenolepis | Mojave cottonthorn | Asteraceae | |
| Tetramerium | tetramerium | Acanthaceae | |
| Tetramerium nervosum | hairy fournwort | Acanthaceae | |
| Tetraneuris | four-nerve daisy | Asteraceae | |
| Tetraneuris acaulis | stemless four-nerve daisy | Asteraceae | |
| Tetraneuris acaulis var. arizonica | Arizona four-nerve daisy | Asteraceae | |
| Tetraneuris argentea | perkysue | Asteraceae | |
| Tetraneuris brandegeei | Brandegee's four-nerve daisy | Asteraceae | |
| Tetraneuris ivesiana | Ives' fournerved daisy | Asteraceae | |
| Teucrium | germander | Lamiaceae | |
| Teucrium canadense | Canada germander | Lamiaceae | |
| Teucrium canadense var. canadense | Canada germander | Lamiaceae | |
| Teucrium canadense var. occidentale | western germander | Lamiaceae | |
| Teucrium cubense | small coastal germander | Lamiaceae | |
| Teucrium cubense var. densum | small coastal germander | Lamiaceae | |
| Teucrium glandulosum | sticky germander | Lamiaceae | |
| Thalictrum | meadow-rue | Ranunculaceae | |
| Thalictrum dasycarpum | purple meadow-rue | Ranunculaceae | |
| Thalictrum fendleri | Fendler's meadow-rue | Ranunculaceae | |
| Thalictrum fendleri var. fendleri | Fendler's meadow-rue | Ranunculaceae | |
| Thalictrum fendleri var. wrightii | Wright's meadow-rue | Ranunculaceae | |
| Thalictrum revolutum | waxyleaf meadow-rue | Ranunculaceae | |
| Thamnosma | desertrue | Rutaceae | |
| Thamnosma montana | turpentinebroom | Rutaceae | |
| Thamnosma texana | rue of the mountains | Rutaceae | |
| Thelesperma | greenthread | Asteraceae | |
| Thelesperma longipes | longstalk greenthread | Asteraceae | |
| Thelesperma megapotamicum | Hopi tea greenthread | Asteraceae | |
| Thelesperma simplicifolium | slender greenthread | Asteraceae | |
| Thelesperma subnudum | Navajo tea | Asteraceae | |
| Thelesperma subnudum var. subnudum | Navajo tea | Asteraceae | |
| Thelypodiopsis | tumblemustard | Brassicaceae | |
| Thelypodiopsis ambigua | Long Valley tumblemustard | Brassicaceae | |
| Thelypodiopsis ambigua var. ambigua | Long Valley tumblemustard | Brassicaceae | |
| Thelypodiopsis ambigua var. erecta | Long Valley tumblemustard | Brassicaceae | |
| Thelypodiopsis purpusii | Purpus' tumblemustard | Brassicaceae | |
| Thelypodium | thelypody | Brassicaceae | |
| Thelypodium integrifolium | entireleaved thelypody | Brassicaceae | |
| Thelypodium integrifolium ssp. gracilipes | entireleaved thelypody | Brassicaceae | |
| Thelypodium integrifolium ssp. longicarpum | entireleaved thelypody | Brassicaceae | |
| Thelypodium wrightii | Wright's thelypody | Brassicaceae | |
| Thelypodium wrightii ssp. wrightii | Wright's thelypody | Brassicaceae | |
| Thelypteris | maiden fern | Thelypteridaceae | |
| Thelypteris puberula | showy maiden fern | Thelypteridaceae | |
| Thelypteris puberula var. sonorensis | Sonoran maiden fern | Thelypteridaceae | |
| Thermopsis | goldenbanner | Fabaceae | |
| Thermopsis montana | mountain goldenbanner | Fabaceae | |
| Thermopsis montana var. montana | mountain goldenbanner | Fabaceae | |
| Thinopyrum | wheatgrass | Poaceae | |
| Thinopyrum intermedium | intermediate wheatgrass | Poaceae | |
| Thinopyrum ponticum | tall wheatgrass | Poaceae | |
| Thlaspi | pennycress | Brassicaceae | |
| Thlaspi arvense | field pennycress | Brassicaceae | |
| Thymophylla | pricklyleaf | Asteraceae | |
| Thymophylla acerosa | pricklyleaf dogweed | Asteraceae | |
| Thymophylla concinna | Sonoran pricklyleaf | Asteraceae | |
| Thymophylla pentachaeta | fiveneedle pricklyleaf | Asteraceae | |
| Thymophylla pentachaeta var. belenidium | fiveneedle pricklyleaf | Asteraceae | |
| Thymophylla pentachaeta var. hartwegii | Hartweg's pricklyleaf | Asteraceae | |
| Thysanocarpus | fringepod | Brassicaceae | |
| Thysanocarpus curvipes | sand fringepod | Brassicaceae | |
| Tidestromia | honeysweet | Amaranthaceae | |
| Tidestromia lanuginosa | woolly tidestromia | Amaranthaceae | |
| Tidestromia oblongifolia | Arizona honeysweet | Amaranthaceae | |
| Tillandsia | airplant | Bromeliaceae | |
| Tillandsia recurvata | small ballmoss | Bromeliaceae | |
| Tiquilia | crinklemat | Boraginaceae | |
| Tiquilia canescens | woody crinklemat | Boraginaceae | |
| Tiquilia canescens var. canescens | woody crinklemat | Boraginaceae | |
| Tiquilia canescens var. pulchella | woody crinklemat | Boraginaceae | |
| Tiquilia latior | matted crinklemat | Boraginaceae | |
| Tiquilia nuttallii | Nuttall's crinklemat | Boraginaceae | |
| Tiquilia palmeri | Palmer's crinklemat | Boraginaceae | |
| Tiquilia plicata | fanleaf crinklemat | Boraginaceae | |
| Tithonia | tithonia | Asteraceae | |
| Tithonia thurberi | Arizona sunflowerweed | Asteraceae | |
| Tordylium | tordylium | Apiaceae | |
| Tordylium apulum | Mediterranean hartwort | Apiaceae | |
| Torilis | hedgeparsley | Apiaceae | |
| Torilis nodosa | knotted hedgeparsley | Apiaceae | |
| Torreyochloa | false mannagrass | Poaceae | |
| Torreyochloa pallida | pale false mannagrass | Poaceae | |
| Torreyochloa pallida var. pauciflora | pale false mannagrass | Poaceae | |
| Townsendia | Townsend daisy | Asteraceae | |
| Townsendia annua | annual Townsend daisy | Asteraceae | |
| Townsendia exscapa | stemless Townsend daisy | Asteraceae | |
| Townsendia formosa | smooth Townsend daisy | Asteraceae | |
| Townsendia incana | hoary Townsend daisy | Asteraceae | |
| Townsendia jonesii | Jones' Townsend daisy | Asteraceae | |
| Townsendia jonesii var. jonesii | Jones' Townsend daisy | Asteraceae | |
| Townsendia leptotes | common Townsend daisy | Asteraceae | |
| Townsendia smithii | Black Rock Townsend daisy | Asteraceae | |
| Toxicodendron | poison oak | Anacardiaceae | |
| Toxicodendron radicans | eastern poison ivy | Anacardiaceae | |
| Toxicodendron radicans ssp. divaricatum | eastern poison ivy | Anacardiaceae | |
| Toxicodendron rydbergii | western poison ivy | Anacardiaceae | |
| Trachypogon | crinkleawn grass | Poaceae | |
| Trachypogon spicatus | spiked crinkleawn | Poaceae | |
| Tradescantia | spiderwort | Commelinaceae | |
| Tradescantia occidentalis | prairie spiderwort | Commelinaceae | |
| Tradescantia occidentalis var. occidentalis | prairie spiderwort | Commelinaceae | |
| Tradescantia occidentalis var. scopulorum | prairie spiderwort | Commelinaceae | |
| Tradescantia pinetorum | pinewoods spiderwort | Commelinaceae | |
| Tragia | noseburn | Euphorbiaceae | |
| Tragia amblyodonta | dogtooth noseburn | Euphorbiaceae | |
| Tragia laciniata | Sonoita noseburn | Euphorbiaceae | |
| Tragia nepetifolia | catnip noseburn | Euphorbiaceae | |
| Tragia nepetifolia var. dissecta | catnip noseburn | Euphorbiaceae | |
| Tragia ramosa | branched noseburn | Euphorbiaceae | |
| Tragopogon | goatsbeard | Asteraceae | |
| Tragopogon dubius | yellow salsify | Asteraceae | |
| Tragopogon lamottei | Jack-go-to-bed-at-noon | Asteraceae | |
| Tragopogon mirus | remarkable goatsbeard | Asteraceae | |
| Tragopogon miscellus | Moscow salsify | Asteraceae | |
| Tragopogon porrifolius | salsify | Asteraceae | |
| Tragus | bur grass | Poaceae | |
| Tragus berteronianus | spiked bur grass | Poaceae | |
| Tragus racemosus | stalked bur grass | Poaceae | |
| Trautvetteria | bugbane | Ranunculaceae | |
| Trautvetteria caroliniensis | Carolina bugbane | Ranunculaceae | |
| Trautvetteria caroliniensis var. occidentalis | western bugbane | Ranunculaceae | |
| Trianthema | trianthema | Aizoaceae | |
| Trianthema portulacastrum | desert horsepurslane | Aizoaceae | |
| Tribulus | puncturevine | Zygophyllaceae | |
| Tribulus terrestris | puncturevine | Zygophyllaceae | |
| Tricardia | tricardia | Hydrophyllaceae | |
| Tricardia watsonii | threehearts | Hydrophyllaceae | |
| Trichloris | Poaceae | ||
| Trichloris crinita | false Rhodes grass | Poaceae | |
| Trichoptilium | trichoptilium | Asteraceae | |
| Trichoptilium incisum | yellowdome | Asteraceae | |
| Trichostema | bluecurls | Lamiaceae | |
| Trichostema arizonicum | Arizona bluecurls | Lamiaceae | |
| Trichostema brachiatum | fluxweed | Lamiaceae | |
| Trichostema micranthum | smallflower bluecurls | Lamiaceae | |
| Tridens | tridens | Poaceae | |
| Tridens albescens | white tridens | Poaceae | |
| Tridens eragrostoides | lovegrass tridens | Poaceae | |
| Tridens muticus | slim tridens | Poaceae | |
| Tridens muticus var. elongatus | slim tridens | Poaceae | |
| Tridens muticus var. muticus | slim tridens | Poaceae | |
| Trifolium | clover | Fabaceae | |
| Trifolium albopurpureum | rancheria clover | Fabaceae | |
| Trifolium amabile | Aztec clover | Fabaceae | |
| Trifolium andinum | Intermountain clover | Fabaceae | |
| Trifolium andinum var. andinum | Intermountain clover | Fabaceae | |
| Trifolium bejariense | Bejar clover | Fabaceae | |
| Trifolium dasyphyllum | alpine clover | Fabaceae | |
| Trifolium dasyphyllum ssp. uintense | Uinta clover | Fabaceae | |
| Trifolium dubium | suckling clover | Fabaceae | |
| Trifolium gracilentum | pinpoint clover | Fabaceae | |
| Trifolium gracilentum var. gracilentum | pinpoint clover | Fabaceae | |
| Trifolium gymnocarpon | hollyleaf clover | Fabaceae | |
| Trifolium gymnocarpon ssp. gymnocarpon | hollyleaf clover | Fabaceae | |
| Trifolium gymnocarpon ssp. plummerae | Plummer's clover | Fabaceae | |
| Trifolium hybridum | alsike clover | Fabaceae | |
| Trifolium kingii | King's clover | Fabaceae | |
| Trifolium kingii ssp. macilentum | King's clover | Fabaceae | |
| Trifolium longipes | longstalk clover | Fabaceae | |
| Trifolium longipes ssp. pygmaeum | pygmy clover | Fabaceae | |
| Trifolium longipes ssp. reflexum | droopflower clover | Fabaceae | |
| Trifolium microcephalum | smallhead clover | Fabaceae | |
| Trifolium mucronatum | cusp clover | Fabaceae | |
| Trifolium mucronatum ssp. lacerum | spinytooth clover | Fabaceae | |
| Trifolium neurophyllum | White Mountain clover | Fabaceae | |
| Trifolium pinetorum | woods clover | Fabaceae | |
| Trifolium pratense | red clover | Fabaceae | |
| Trifolium repens | white clover | Fabaceae | |
| Trifolium variegatum | whitetip clover | Fabaceae | |
| Trifolium willdenovii | tomcat clover | Fabaceae | |
| Trifolium wormskioldii | cows clover | Fabaceae | |
| Triglochin | arrowgrass | Juncaginaceae | |
| Triglochin maritima | seaside arrowgrass | Juncaginaceae | |
| Triglochin palustris | marsh arrowgrass | Juncaginaceae | |
| Triodanis | Venus' looking-glass | Campanulaceae | |
| Triodanis biflora | small Venus' looking-glass | Campanulaceae | |
| Triodanis holzingeri | Holzinger's Venus' looking-glass | Campanulaceae | |
| Triodanis perfoliata | clasping Venus' looking-glass | Campanulaceae | |
| Tripsacum | gamagrass | Poaceae | |
| Tripsacum lanceolatum | Mexican gamagrass | Poaceae | |
| Tripterocalyx | sandpuffs | Nyctaginaceae | |
| Tripterocalyx carneus | winged sandpuffs | Nyctaginaceae | |
| Tripterocalyx carneus var. wootonii | Wooton's sandpuffs | Nyctaginaceae | |
| Tripterocalyx micranthus | smallflower sandverbena | Nyctaginaceae | |
| Trisetum | oatgrass | Poaceae | |
| Trisetum canescens | tall trisetum | Poaceae | |
| Trisetum interruptum | prairie false oat | Poaceae | |
| Trisetum spicatum | spike trisetum | Poaceae | |
| Triteleia | triteleia | Liliaceae | |
| Triteleia lemmoniae | Oak Creek triteleia | Liliaceae | |
| Triteleiopsis | Bajalily | Liliaceae | |
| Triteleiopsis palmeri | Palmer's Bajalily | Liliaceae | |
| Triticum | wheat | Poaceae | |
| Triticum aestivum | common wheat | Poaceae | |
| Trixis | threefold | Asteraceae | |
| Trixis californica | American threefold | Asteraceae | |
| Tumamoca | tumamoca | Cucurbitaceae | |
| Tumamoca macdougalii | Tumamoc globeberry | Cucurbitaceae | |
| Typha | cattail | Typhaceae | |
| Typha domingensis | southern cattail | Typhaceae | |
| Typha latifolia | broadleaf cattail | Typhaceae | |
| U | |||
| Ulmus | elm | Ulmaceae | |
| Ulmus parvifolia | Chinese elm | Ulmaceae | |
| Ulmus pumila | Siberian elm | Ulmaceae | |
| Urochloa | signalgrass | Poaceae | |
| Urochloa arizonica | Arizona signalgrass | Poaceae | |
| Urochloa fusca | browntop signalgrass | Poaceae | |
| Urochloa maxima | guineagrass | Poaceae | |
| Urochloa panicoides | panic liverseed grass | Poaceae | |
| Urochloa platyphylla | broadleaf signalgrass | Poaceae | |
| Urochloa texana | Texas signalgrass | Poaceae | |
| Urtica | nettle | Urticaceae | |
| Urtica dioica | stinging nettle | Urticaceae | |
| Urtica dioica ssp. gracilis | California nettle | Urticaceae | |
| Urtica dioica ssp. holosericea | stinging nettle | Urticaceae | |
| Urtica gracilenta | mountain nettle | Urticaceae | |
| Urtica urens | dwarf nettle | Urticaceae | |
| Utricularia | bladderwort | Lentibulariaceae | |
| Utricularia macrorhiza | common bladderwort | Lentibulariaceae | |
| Utricularia minor | lesser bladderwort | Lentibulariaceae | |
| V | |||
| Vaccaria | soapwort | Caryophyllaceae | |
| Vaccaria hispanica | cow soapwort | Caryophyllaceae | |
| Vaccinium | blueberry | Ericaceae | |
| Vaccinium geminiflorum | Mexican blueberry | Ericaceae | |
| Vaccinium membranaceum | thinleaf huckleberry | Ericaceae | |
| Vaccinium myrtillus | whortleberry | Ericaceae | |
| Valeriana | valerian | Valerianaceae | |
| Valeriana acutiloba | sharpleaf valerian | Valerianaceae | |
| Valeriana acutiloba var. acutiloba | sharpleaf valerian | Valerianaceae | |
| Valeriana arizonica | Arizona valerian | Valerianaceae | |
| Valeriana edulis | tobacco root | Valerianaceae | |
| Valeriana edulis var. edulis | tobacco root | Valerianaceae | |
| Valeriana occidentalis | western valerian | Valerianaceae | |
| Valeriana sorbifolia | pineland valerian | Valerianaceae | |
| Vallisneria | eelgrass | Hydrocharitaceae | |
| Vallisneria americana | American eelgrass | Hydrocharitaceae | |
| Vanclevea | vanclevea | Asteraceae | |
| Vanclevea stylosa | pillar false gumweed | Asteraceae | |
| Vauquelinia | rosewood | Rosaceae | |
| Vauquelinia californica | Arizona rosewood | Rosaceae | |
| Vauquelinia californica ssp. californica | Arizona rosewood | Rosaceae | |
| Vauquelinia californica ssp. pauciflora | Arizona rosewood | Rosaceae | |
| Vauquelinia californica ssp. sonorensis | Sonora rosewood | Rosaceae | |
| Veratrum | false hellebore | Liliaceae | |
| Veratrum californicum | California false hellebore | Liliaceae | |
| Veratrum californicum var. californicum | California false hellebore | Liliaceae | |
| Verbascum | mullein | Scrophulariaceae | |
| Verbascum blattaria | moth mullein | Scrophulariaceae | |
| Verbascum thapsus | common mullein | Scrophulariaceae | |
| Verbascum virgatum | wand mullein | Scrophulariaceae | |
| Verbena | vervain | Verbenaceae | |
| Verbena bonariensis | purpletop vervain | Verbenaceae | |
| Verbena bonariensis var. bonariensis | purpletop vervain | Verbenaceae | |
| Verbena bracteata | bigbract verbena | Verbenaceae | |
| Verbena carolina | Carolina vervain | Verbenaceae | |
| Verbena ehrenbergiana | Ehrenberg's vervain | Verbenaceae | |
| Verbena gracilis | Fort Huachuca vervain | Verbenaceae | |
| Verbena halei | Texas vervain | Verbenaceae | |
| Verbena hastata | swamp verbena | Verbenaceae | |
| Verbena hastata var. scabra | swamp verbena | Verbenaceae | |
| Verbena macdougalii | MacDougal verbena | Verbenaceae | |
| Verbena menthifolia | mint vervain | Verbenaceae | |
| Verbena neomexicana | hillside vervain | Verbenaceae | |
| Verbena neomexicana var. hirtella | hillside vervain | Verbenaceae | |
| Verbena neomexicana var. neomexicana | hillside vervain | Verbenaceae | |
| Verbena neomexicana var. xylopoda | hillside vervain | Verbenaceae | |
| Verbena perennis | pinleaf vervain | Verbenaceae | |
| Verbena pinetorum | Chihuahuan vervain | Verbenaceae | |
| Verbena plicata | fanleaf vervain | Verbenaceae | |
| Verbena scabra | sandpaper vervain | Verbenaceae | |
| Verbena stricta | hoary verbena | Verbenaceae | |
| Verbena xutha | Gulf vervain | Verbenaceae | |
| Verbesina | crownbeard | Asteraceae | |
| Verbesina encelioides | golden crownbeard | Asteraceae | |
| Verbesina encelioides ssp. exauriculata | golden crownbeard | Asteraceae | |
| Verbesina longifolia | longleaf crownbeard | Asteraceae | |
| Verbesina rothrockii | Rothrock's crownbeard | Asteraceae | |
| Vernonia | ironweed | Asteraceae | |
| Vernonia marginata | plains ironweed | Asteraceae | |
| Veronica | speedwell | Scrophulariaceae | |
| Veronica americana | American speedwell | Scrophulariaceae | |
| Veronica anagallis-aquatica | water speedwell | Scrophulariaceae | |
| Veronica arvensis | corn speedwell | Scrophulariaceae | |
| Veronica peregrina | neckweed | Scrophulariaceae | |
| Veronica peregrina ssp. xalapensis | hairy purslane speedwell | Scrophulariaceae | |
| Veronica persica | birdeye speedwell | Scrophulariaceae | |
| Veronica polita | gray field speedwell | Scrophulariaceae | |
| Veronica serpyllifolia | thymeleaf speedwell | Scrophulariaceae | |
| Veronica serpyllifolia ssp. humifusa | brightblue speedwell | Scrophulariaceae | |
| Veronica wormskjoldii | American alpine speedwell | Scrophulariaceae | |
| Veronica wormskjoldii var. wormskjoldii | American alpine speedwell | Scrophulariaceae | |
| Vicia | vetch | Fabaceae | |
| Vicia americana | American vetch | Fabaceae | |
| Vicia americana ssp. americana | American vetch | Fabaceae | |
| Vicia americana ssp. minor | mat vetch | Fabaceae | |
| Vicia leucophaea | Mogollon Mountain vetch | Fabaceae | |
| Vicia ludoviciana | Louisiana vetch | Fabaceae | |
| Vicia ludoviciana ssp. ludoviciana | Louisiana vetch | Fabaceae | |
| Vicia pulchella | sweetclover vetch | Fabaceae | |
| Vicia sativa | garden vetch | Fabaceae | |
| Vicia sativa ssp. nigra | garden vetch | Fabaceae | |
| Vicia villosa | winter vetch | Fabaceae | |
| Vicia villosa ssp. villosa | winter vetch | Fabaceae | |
| Viguiera | goldeneye | Asteraceae | |
| Viguiera cordifolia | heartleaf goldeneye | Asteraceae | |
| Viguiera dentata | toothleaf goldeneye | Asteraceae | |
| Viguiera dentata var. dentata | toothleaf goldeneye | Asteraceae | |
| Viguiera dentata var. lancifolia | toothleaf goldeneye | Asteraceae | |
| Viguiera parishii | Parish's goldeneye | Asteraceae | |
| Viguiera triloba | yellow streamers | Asteraceae | |
| Vinca | periwinkle | Apocynaceae | |
| Vinca major | bigleaf periwinkle | Apocynaceae | |
| Vinca minor | common periwinkle | Apocynaceae | |
| Viola | violet | Violaceae | |
| Viola adunca | hookedspur violet | Violaceae | |
| Viola adunca var. adunca | hookedspur violet | Violaceae | |
| Viola bicolor | field pansy | Violaceae | |
| Viola canadensis | Canadian white violet | Violaceae | |
| Viola canadensis var. rugulosa | creepingroot violet | Violaceae | |
| Viola canadensis var. scariosa | Canadian white violet | Violaceae | |
| Viola nephrophylla | northern bog violet | Violaceae | |
| Viola odorata | sweet violet | Violaceae | |
| Viola palustris | marsh violet | Violaceae | |
| Viola palustris var. brevipes | marsh violet | Violaceae | |
| Viola pedatifida | prairie violet | Violaceae | |
| Viola purpurea | goosefoot violet | Violaceae | |
| Viola purpurea ssp. mohavensis | goosefoot violet | Violaceae | |
| Viola umbraticola | Ponderosa violet | Violaceae | |
| Viola umbraticola var. glaberrima | Ponderosa violet | Violaceae | |
| Viola vallicola | sagebrush violet | Violaceae | |
| Viola vallicola var. vallicola | sagebrush violet | Violaceae | |
| Vitex | chastetree | Verbenaceae | |
| Vitex agnus-castus | lilac chastetree | Verbenaceae | |
| Vitex agnus-castus var. agnus-castus | lilac chastetree | Verbenaceae | |
| Vitis | grape | Vitaceae | |
| Vitis arizonica | canyon grape | Vitaceae | |
| Vulpia | fescue | Poaceae | |
| Vulpia bromoides | brome fescue | Poaceae | |
| Vulpia microstachys | small fescue | Poaceae | |
| Vulpia microstachys var. ciliata | Eastwood fescue | Poaceae | |
| Vulpia microstachys var. microstachys | desert fescue | Poaceae | |
| Vulpia microstachys var. pauciflora | Pacific fescue | Poaceae | |
| Vulpia myuros | rat-tail fescue | Poaceae | |
| Vulpia octoflora | sixweeks fescue | Poaceae | |
| Vulpia octoflora var. glauca | sixweeks fescue | Poaceae | |
| Vulpia octoflora var. hirtella | sixweeks fescue | Poaceae | |
| Vulpia octoflora var. octoflora | sixweeks fescue | Poaceae | |
| W | |||
| Waltheria | waltheria | Sterculiaceae | |
| Waltheria indica | uhaloa | Sterculiaceae | |
| Washingtonia | fan palm | Arecaceae | |
| Washingtonia filifera | California fan palm | Arecaceae | |
| Wislizenia | wislizenia | Capparaceae | |
| Wislizenia refracta | spectacle fruit | Capparaceae | |
| Wislizenia refracta ssp. refracta | spectacle fruit | Capparaceae | |
| Woodsia | cliff fern | Dryopteridaceae | |
| Woodsia cochisensis | Cochise cliff fern | Dryopteridaceae | |
| Woodsia neomexicana | New Mexico cliff fern | Dryopteridaceae | |
| Woodsia oregana | Oregon cliff fern | Dryopteridaceae | |
| Woodsia oregana ssp. cathcartiana | Oregon cliff fern | Dryopteridaceae | |
| Woodsia phillipsii | Phillips' cliff fern | Dryopteridaceae | |
| Woodsia plummerae | Plummer's cliff fern | Dryopteridaceae | |
| Woodsia scopulina | Rocky Mountain woodsia | Dryopteridaceae | |
| Woodsia scopulina ssp. laurentiana | Laurent's cliff fern | Dryopteridaceae | |
| Woodwardia | chainfern | Blechnaceae | |
| Woodwardia fimbriata | giant chainfern | Blechnaceae | |
| Wyethia | mule-ears | Asteraceae | |
| Wyethia arizonica | Arizona mule-ears | Asteraceae | |
| X | |||
| Xanthisma | sleepydaisy | Asteraceae | |
| Xanthisma texanum | Texas sleepydaisy | Asteraceae | |
| Xanthisma texanum ssp. drummondii | Drummond's sleepydaisy | Asteraceae | |
| Xanthium | cocklebur | Asteraceae | |
| Xanthium spinosum | spiny cocklebur | Asteraceae | |
| Xanthium strumarium | rough cocklebur | Asteraceae | |
| Xanthium strumarium var. canadense | Canada cocklebur | Asteraceae | |
| Xanthocephalum | xanthocephalum | Asteraceae | |
| Xanthocephalum gymnospermoides | San Pedro matchweed | Asteraceae | |
| Xylorhiza | woodyaster | Asteraceae | |
| Xylorhiza tortifolia | Mojave woodyaster | Asteraceae | |
| Xylorhiza tortifolia var. imberbis | imberis woodyaster | Asteraceae | |
| Xylorhiza tortifolia var. tortifolia | Mojave woodyaster | Asteraceae | |
| Y | |||
| Yabea | yabea | Apiaceae | |
| Yabea microcarpa | false carrot | Apiaceae | |
| Yucca | yucca | Agavaceae | |
| Yucca angustissima | narrowleaf yucca | Agavaceae | |
| Yucca angustissima var. angustissima | narrowleaf yucca | Agavaceae | |
| Yucca angustissima var. kanabensis | Kanab yucca | Agavaceae | |
| Yucca baccata | banana yucca | Agavaceae | |
| Yucca baileyi | Navajo yucca | Agavaceae | |
| Yucca baileyi var. baileyi | Navajo yucca | Agavaceae | |
| Yucca baileyi var. navajoa | Navajo yucca | Agavaceae | |
| Yucca brevifolia | Joshua tree | Agavaceae | |
| Yucca brevifolia var. brevifolia | Joshua tree | Agavaceae | |
| Yucca brevifolia var. jaegeriana | Jaeger's Joshua tree | Agavaceae | |
| Yucca elata | soaptree yucca | Agavaceae | |
| Yucca harrimaniae | Spanish bayonet | Agavaceae | |
| Yucca harrimaniae var. harrimaniae | Spanish bayonet | Agavaceae | |
| Yucca karlsruhensis | Agavaceae | ||
| Yucca madrensis | Agavaceae | ||
| Yucca schidigera | Mojave yucca | Agavaceae | |
| Yucca schottii | Schott's yucca | Agavaceae | |
| Z | |||
| Zannichellia | horned pondweed | Zannichelliaceae | |
| Zannichellia palustris | horned pondweed | Zannichelliaceae | |
| Zapoteca | white stickpea | Fabaceae | |
| Zapoteca formosa | Schott's stickpea | Fabaceae | |
| Zapoteca formosa var. schottii | Schott's stickpea | Fabaceae | |
| Zea | corn | Poaceae | |
| Zea mays | corn | Poaceae | |
| Zea mays ssp. mays | corn | Poaceae | |
| Zephyranthes | zephyrlily | Liliaceae | |
| Zephyranthes longifolia | copper zephyrlily | Liliaceae | |
| Zigadenus | deathcamas | Liliaceae | |
| Zigadenus elegans | mountain deathcamas | Liliaceae | |
| Zigadenus elegans ssp. elegans | mountain deathcamas | Liliaceae | |
| Zigadenus paniculatus | foothill deathcamas | Liliaceae | |
| Zigadenus virescens | green deathcamas | Liliaceae | |
| Zinnia | zinnia | Asteraceae | |
| Zinnia acerosa | desert zinnia | Asteraceae | |
| Zinnia grandiflora | Rocky Mountain zinnia | Asteraceae | |
| Zinnia peruviana | Peruvian zinnia | Asteraceae | |
| Zizania | wildrice | Poaceae | |
| Zizania palustris | northern wildrice | Poaceae | |
| Zizania palustris var. palustris | northern wildrice | Poaceae | |
| Ziziphus | jujube | Rhamnaceae | |
| Ziziphus obtusifolia | lotebush | Rhamnaceae | |
| Ziziphus obtusifolia var. canescens | lotebush | Rhamnaceae | |
| Ziziphus obtusifolia var. obtusifolia | lotebush | Rhamnaceae | |
| Zornia | zornia | Fabaceae | |
| Zornia leptophylla | horsekiller | Fabaceae | |
| Zornia reticulata | neto hoja zarzabacoa de dos hojas | Fabaceae | |
| Zuckia | zuckia | Chenopodiaceae | |
| Zuckia brandegeei | siltbush | Chenopodiaceae | |
| Zuckia brandegeei var. arizonica | Arizona siltbush | Chenopodiaceae | |
| Zuckia brandegeei var. brandegeei | siltbush | Chenopodiaceae |