Machaeranthera tagetina – Mesa Tansyaster
Scientific Name: Machaeranthera tagetina
Synonym: Aster tagetinus
Common Names: Mesa Tansyaster, Mesa Tansy-aster
Growth Habit: Herb/Forb
Arizona Native Status: Native
Habitat: Desert, Upland
Flower Color: Purple
Flowering Season: Summer, Fall. This wildflower blooms after the summer monsoon rains have begun.
Height: Up to 20 inches (50 cm) tall
Description: The flower heads have 8 to 16 purple rays, golden yellow disks, and 24 to 44 lance-shaped, appressed to spreading, point-tipped or spine-tipped phyllaries (bracts at the base of the flower heads) in 3 to 5 series. The phyllaries have leafy, green, glandular-hairy tips and white, mostly hairless bases. The flower heads are followed by fluffy, rounded, whitish seed heads. The leaves are green, alternate, spine-tipped, and pinnatifid except near the stem tips. The stems are slender, green, and branched. The stems and leaves are minutely hairy with a mixture of regular and gland-tipped hairs.
The similar Machaeranthera tanacetifolia has fernlike or tansy-like, once or twice pinnatifid leaves and flowers with usually many more rays and phyllaries. Arida arizonica (Machaeranthera arida) has flowers with more rays. Arida parviflora (Machaeranthera parviflora) has wiry stems and flowers with smaller phyllaries and usually more rays. Almutaster pauciflorus (Aster pauciflorus), Arida riparia (Machaeranthera riparia), Dieteria asteroides (Machaeranthera asteroides), Dieteria bigelovii (Machaeranthera bigelovii), Dieteria canescens (Machaeranthera canescens), Psilactis asteroides, and Psilactis gentryi all have non-pinnatifid leaves.
Kingdom: Plantae – Plants
Subkingdom: Tracheobionta – Vascular plants
Superdivision: Spermatophyta – Seed plants
Division: Magnoliophyta – Flowering plants
Class: Magnoliopsida – Dicotyledons
Family: Asteraceae – Aster family
Genus: Machaeranthera Nees – tansyaster
Species: Machaeranthera tagetina Greene – mesa tansyaster
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