Camissonia is a genus of annual and perennial flowering plants in the evening primrose family, Onagraceae, placed within the order Myrtales. Commonly known as sun cups or sundrops, the genus comprises around 12 accepted species — a significant reduction from earlier treatments that recognized up to 62 species before the group was divided among closely related genera.
The flowers are a characteristic bright yellow, typically opening at dawn and arranged in cup-shaped form that gives rise to the common names. Camissonia is distinguished from the closely related genus Oenothera by its club- or head-shaped stigma, in contrast to the four-lobed stigma of Oenothera.
Nearly all species are native to western North America, with a particular concentration in the California Floristic Province — a global biodiversity hotspot noted for its high proportion of endemic plant species. One species, Camissonia dentata, extends the genus's range to South America. The genus was formerly included within Oenothera before being separated on morphological grounds; subsequent molecular and taxonomic revision further reduced and redefined its circumscription.
Camissonia species play a role in local food webs: the larvae of several moth species in the genus Schinia use them as host plants, with Schinia deserticola feeding exclusively on Camissonia claviformis.
Etymology
The genus name Camissonia honors the German-French Romantic poet and naturalist Adelbert von Chamisso (1781–1838), who collected plants during a Russian circumnavigation expedition and made significant contributions to Pacific and Californian botany.
Distribution
Camissonia is found predominantly in western North America, with species concentrated in the California Floristic Province. The range extends across arid and semi-arid habitats of the western United States. One species, Camissonia dentata, occurs in South America.
Ecology
Species of Camissonia serve as larval food plants for moths in the genus Schinia, including Schinia cupes and Schinia deserticola. Schinia deserticola feeds exclusively on Camissonia claviformis, illustrating a tight specialist herbivore relationship common among Onagraceae of the California Floristic Province.
Taxonomy Notes
Camissonia was originally circumscribed within Oenothera and later separated as a distinct genus. At its broadest, the genus held up to 62 species; modern molecular and morphological revision has reduced it to approximately 12 accepted species, with many former members redistributed to genera such as Chylismia, Eremothera, and Tetrapteron. The key diagnostic character separating Camissonia from Oenothera is the club- or head-shaped (capitate) stigma rather than the four-lobed stigma of Oenothera.
