Lasthenia, commonly known as goldfields, is a genus of annual (rarely perennial) flowering herbs in the family Asteraceae (order Asterales). The genus comprises about 18 species, 17 of which are native to North America — the vast majority endemic to California — with one species, Lasthenia kunthii, occurring only in Chile.
Plants are typically small, branched, and erect, reaching less than 60 cm in height. The opposite leaves, up to 20 cm long, have entire margins and pinnate venation. Each stem terminates in a solitary flower head (sometimes arranged in cymes) bearing 4 to 16 yellow ray florets surrounding numerous yellow disk florets with 5-lobed corollae. Fruits are small (under 5 mm), cylindric to obovoid, black or gray, and may bear a pappus of awns or scales. The genus is predominantly cross-pollinated, with insects — including Sciaridae fungus gnats — serving as pollinators.
Goldfields are strongly associated with vernal pools and ephemeral wetlands, as well as coastal scrub, semiarid meadows, and open woodland across California and the broader Pacific Coast. Several species are conservation-sensitive: Lasthenia conjugens (Contra Costa goldfields) and Lasthenia burkei (Burke's goldfields) are listed as endangered in the United States.
Etymology
The genus name Lasthenia honors Lasthenia of Mantinea, a woman said to have disguised herself as a man in order to study philosophy under Plato in ancient Athens. The common name "goldfields" refers to the striking yellow carpets these plants create when blooming en masse across open grasslands and vernal pools.
Distribution
Goldfields are predominantly a California genus: of the 18 recognized species, 17 are native to North America (most concentrated in California, with a few extending into Oregon, Washington, British Columbia, Arizona, and northern Mexico) and one (L. kunthii) is restricted to Chile. They favor semiarid conditions and are particularly characteristic of vernal pools, coastal bluffs, and seasonal wetlands along the Pacific Coast.
Ecology
Lasthenia species colonize a range of open, often seasonally wet or semiarid habitats: ephemeral pools, coastal prairies, meadows, shrubland, and open woodland. They are ecologically important components of California vernal pool plant communities. Sciaridae fungus gnats have been recorded visiting flowers for nectar and are suspected to be significant pollinators, particularly for the endangered Contra Costa goldfields (L. conjugens). The genus is generally cross-pollinated and depends on insect visitation.
Conservation
At least two species carry formal threatened status in the United States. Lasthenia conjugens (Contra Costa goldfields) and Lasthenia burkei (Burke's goldfields) are listed as endangered, both restricted to California. Loss and degradation of vernal pool habitat — through urban development, agriculture, and altered hydrology — is the principal threat to these and other range-restricted species in the genus.
