Plant Name
Scientific Name: Dieteria canescens
Synonyms: Aster canescens, Machaeranthera canescens
Common Names: Hoary Tansyaster, Hoary Tansy-aster, Hoary-aster, Purple Aster
Plant Characteristics
Duration: Annual, Biennial, Perennial
Growth Habit: Herb/Forb
Arizona Native Status: Native
Habitat: Desert, Upland
Flower Color: Purple, White (rare)
Flowering Season: Late spring, Summer, Fall
Height: Up to 4 feet (1.2 m) tall
Description: The flower heads have numerous, slender, purple rays, golden yellow disks, and appressed, spreading, or reflexed phyllaries (bracts at the base of the flower heads) with green, hairy, pointed or spiny tips and mostly hairless, greenish white bases. The flower heads are followed by bristly, rounded, tan-colored seed heads. The leaves are green, alternate, linear to narrowly lance-shaped, and either smooth-edged or edged with small, spine-tipped teeth. The stems are slender, green, erect, and openly branched above. The leaves, stems, and flower stalks are variably hairy grayish white, finely hairy, or sometimes hairless, and they may have a few stalked glandular hairs mixed in with the other types of hairs.
The very similar Dieteria bigelovii (Machaeranthera bigelovii) has flowers with both sticky, very glandular-hairy stalks and phyllaries. Dieteria asteroides (Machaeranthera asteroides) has flowers with solid green phyllaries that have both hairy tips and bases. Almutaster pauciflorus (Aster pauciflorus) has flowers with green, glandular-hairy phyllaries. Arida arizonica (Machaeranthera arida) is only up to 16 inches (40 cm) tall and has small flower heads and pinnatifid or coarsely toothed leaves. Arida riparia (Machaeranthera riparia) is only up to 2 feet (60 cm) tall and has flowers with appressed phyllaries, long, narrowly linear leaves, and just a few spiny teeth on only the basal leaves. Psilactis asteroides has untoothed leaves with wedge-shaped to slightly heart-shaped bases and flowers with green phyllaries. Psilactis gentryi has untoothed leaves with either clasping, heart-shaped leaf bases or a pair of basal lobes. Arida parviflora (Machaeranthera parviflora), Machaeranthera tagetina, and Machaeranthera tanacetifolia have pinnatifid leaves.
Classification
Kingdom: Plantae – Plants
Subkingdom: Tracheobionta – Vascular plants
Superdivision: Spermatophyta – Seed plants
Division: Magnoliophyta – Flowering plants
Class: Magnoliopsida – Dicotyledons
Subclass: Asteridae
Order: Asterales
Family: Asteraceae – Aster family
Genus: Dieteria Nutt. – tansyaster
Species: Dieteria canescens (Pursh) Nutt. – hoary tansyaster