Holocarpha obconica
San joaquin tarweed
(c) Ken-ichi Ueda, some rights reserved (CC BY) · licence
Family: Asteraceae · Type: Herb · Native
Holocarpha obconica (San joaquin tarweed) is a native California herb in the Asteraceae family, recognized by resinous but not stalked-glandular stems, flat-topped clusters distinguish it.
San joaquin tarweed is a California native annual found in southern Sierra Nevada Foothills, northwestern San Joaquin Valley, eastern San Francisco Bay Area, and eastern South Coast Ranges in grassland habitats at elevations below 500 meters. Flowering from April to November, this plant produces yellow flowers with 4 to 9 ray flowers and 11 to 21 yellow to brownish disk flowers in flat-topped or panicle-like clusters. Growing 1 to 8 decimeters tall with slightly resinous stems that are not notably stalked-glandular, it has a distinctive branching structure. Its involucre is approximately obconic to spherical, with phyllaries featuring 5 to 15 pit-gland-tipped outgrowths and generally glabrous or minutely glandular surfaces. The plant's compact, clustered flower heads and resinous stems make it a characteristic element of California's grassland ecosystems.
Identification and appearance
Key characters: 2 sympatric species; resinous but not stalked-glandular stems, flat-topped clusters distinguish it
Habitat and range
Habitat: Grassland
Elevation: < 500 m
Bloom period
Holocarpha obconica blooms Apr-Nov.
How to tell it apart
vs Deinandra: Holocarpha has pit-gland-tipped stalk bracts; Deinandra stalk bracts lack pit glands.; vs Madia: Holocarpha has pit glands on stalk bracts; Madia lacks these distinctive pit glands.; vs Hemizonia: Holocarpha has pit-gland-tipped stalk bracts; Hemizonia stalk bracts lack pit glands.; vs Heterotheca: Holocarpha has yellow rays and pit-gland bracts; Heterotheca lacks pit glands, different flower structure.; vs Centromadia: Holocarpha has pit-gland-tipped stalk bracts; Centromadia lacks pit glands on bracts.
Frequently asked questions
Is Holocarpha obconica native to California?
Yes. Holocarpha obconica is native to California (recorded as native).
When does Holocarpha obconica bloom?
Holocarpha obconica blooms Apr-Nov.
What plant family does Holocarpha obconica belong to?
Holocarpha obconica is in the Asteraceae family, genus Holocarpha.
What habitat does Holocarpha obconica grow in?
Holocarpha obconica grows in Grassland.
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.