Holocarpha obconica, commonly known as the San Joaquin tarweed, is a North American plant species in the sunflower family. It is endemic to (found only in) California, primarily in the Central Valley and adjacent regions.CalFlora taxon report, University of California, Holocarpha obconica (J. Clausen & Keck) Keck, San Joaquin tarweed . accessed 11.14.2011.
The epithet "obconica" means "obconical," in other words, shaped like a cone, but with the widest part furthest from the base. Achenes of H. obconica are obconical. The plant is a resin-containing herb up to 120 cm (4 feet) tall. It produces numerous flower heads, each head containing 4–9 yellow ray flowers surrounding 11–21 small yellow disc flowers, the disc flowers having yellow or brown anthers.Flora of North America, Holocarpha obconica (J. C. Clausen & D. D. Keck) D. D. Keck, 1958. Clausen, Jens Christian & Keck, David Daniels. 1935. Madroño 3(1): 7, Hemizonia obconica
References
External links photo of herbarium specimen at Missouri Botanical Garden, collected in Alameda County in 1933, isotype of Holocarpha obconica Calphotos photo gallery, University of California