Calistoga Popcornflower

(Plagiobothrys strictus)

Calistoga popcornflower is a California threatened plant species, which means that killing or possessing this plant is prohibited by the California Endangered Species Act (CESA). This species is also listed as endangered under the federal Endangered Species Act. Calistoga popcornflower is an annual herb in the borage family (Boraginaceae), and it grows from 4 to 16 inches tall. It has slender stems with narrow leaves, and small white flowers that typically appear in March and April in a slender, unbranched inflorescence.

Calistoga popcornflower grows in pools and swales adjacent to hot springs and geysers in annual grassland habitats. This species grows on clay soils containing high concentrations of boron, arsenic, and sulfates. Calistoga popcornflower is only known from two locations near the town of Calistoga in Napa County, where it co-occurs with the California endangered Napa bluegrass (Napa bluegrass (Poa napensis)).

Calistoga popcornflower is highly vulnerable to extinction due to its restricted range and small number of populations. Both populations of this species are located on privately-owned land and neither site is permanently protected. Threats to this species include potential habitat loss due to development or changing land use, potential alteration of geothermal or surface water hydrology, and competition with invasive plant species. Climate change may also threaten the survival of this species.

Long-term survival of Calistoga popcornflower is dependent upon coordination with private landowners to protect the two known populations of this species, and to reduce or eliminate threats due to hydrological changes or competition with invasive plant species. Seeds should be collected from both populations and placed into long-term storage at a qualified seed banking facility affiliated with the Center for Plant Conservation, and populations should be surveyed and an ongoing, standardized monitoring program should be implemented. Research into the species’ specific habitat requirements should also be conducted.

CDFW may issue permits for Calistoga popcornflower pursuant to CESA, and you can learn more about the California laws protecting Calistoga popcornflower and other California native plants. Populations of Calistoga popcornflower occur in CDFW’s Bay Delta Region. More information is also available from the U.S. Fish and Wildlife Service Species Profile for Calistoga Popcornflower.

Updated 01/15/2014

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Plagiobothrys strictus, CDFW file photo
Plagiobothrys strictus, CDFW file photo
Plagiobothrys strictus CDFW illustration by Mary Ann Showers, click for full-sized image
Plagiobothrys strictus CDFW illustration by Mary Ann Showers, click for full-sized image