Machaeranthera tagetina – Mesa Tansyaster

Machaeranthera tagetina - Mesa Tansyaster, Mesa Tansy-aster (flower)

Machaeranthera tagetina - Mesa Tansyaster, Mesa Tansy-aster (flower)

Machaeranthera tagetina - Mesa Tansyaster, Mesa Tansy-aster

Plant Name

Scientific Name: Machaeranthera tagetina

Synonym: Aster tagetinus

Common Names: Mesa Tansyaster, Mesa Tansy-aster

Plant Characteristics

Duration: Annual

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
Subclass: Asteridae
Order: Asterales
Family: Asteraceae – Aster family
Genus: Machaeranthera Nees – tansyaster
Species: Machaeranthera tagetina Greene – mesa tansyaster

More About This Plant

Arizona County Distribution Map