Hemizonia congesta
Hayfield tarweed
(c) Bruce Homer-Smith, some rights reserved (CC BY) · licence
Family: Asteraceae · Type: Herb · Native
Hemizonia congesta (Hayfield tarweed) is a native California herb in the Asteraceae family, recognized by Sole CA Hemizonia; aromatic annual tarweed of coast ranges/valley margin; congeners are all its own subspecies.
Hayfield tarweed is a California native annual found in grasslands and agricultural areas across the state's central and coastal regions. Flowering from May to October, this plant produces delicate white to yellow ray flowers with purple veins, often arranged in compact clusters with heads 3 to 8 millimeters in diameter. Growing with erect stems 15 to 80 centimeters tall, it has an often aromatic quality with a variable growth habit. Its leaves are distinctively narrow, ranging from 5 to 18 centimeters long and 2 to 8 millimeters wide, with a linear to lance-linear shape and minutely serrated edges, covered in fine puberulent or silky hairs. The plant is particularly notable for its intricate flower heads with 5 to 14 ray flowers and dark purple anthers that add visual complexity to its appearance.
Identification and appearance
Key characters: Sole CA Hemizonia; aromatic annual tarweed of coast ranges/valley margin; congeners are all its own subspecies
How to tell it apart
vs Deinandra: Hemizonia rays often purple-veined beneath; Deinandra rays pure yellow without veining.; vs Madia: Hemizonia has paleae throughout disk; Madia has ray fruits enclosed by phyllaries.; vs Calycadenia: Hemizonia rays shallowly lobed; Calycadenia rays deeply split into spreading lobes.; vs Holocarpha: Hemizonia lacks pit glands on stalks; Holocarpha has distinctive pit-gland-tipped stalk bracts.; vs Anisocarpus: Hemizonia has chaff throughout flower disk; Anisocarpus typically lacks chaff scales.
Frequently asked questions
Is Hemizonia congesta native to California?
Yes. Hemizonia congesta is native to California (recorded as native).
What plant family does Hemizonia congesta belong to?
Hemizonia congesta is in the Asteraceae family, genus Hemizonia.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.