Presidio clarkia is listed as a California endangered plant species, which means that killing or possessing this plant is prohibited by the California Endangered Species Act (CESA). Presidio clarkia is also listed as endangered under the federal Endangered Species Act. Presidio clarkia is an herbaceous annual in the evening-primrose family (Onagraceae). During May and June, delicate pink flowers bloom at the end of slender, erect stems that are about four centimeters long. This species is only known to grow in two locations, the Oakland Hills and San Francisco’s Presidio. The populations on the Presidio are on public lands owned by the National Park Service and co-managed by the Golden Gate National Recreation Area and Presidio Trust. One of the populations in the Oakland Hills is protected on public land owned by the East Bay Regional Park District (EBRPD), but the other populations are on private land. Presidio clarkia is restricted to serpentine soils in grassland and coastal scrub communities and it prefers habitats unobstructed by shade.
Presidio clarkia is adapted to the harsh conditions of nutrient poor serpentine soils that prevent many other plants from growing. A primary threat to Presidio clarkia is destruction and alteration of its serpentine habitat. Fire suppression, elevated nitrogen deposition from air pollution, climate change, human disturbance and gopher populations all have the potential to alter Presidio clarkia habitat and exacerbate the threat of nonnative plants. Road maintenance and vegetation management have been eliminated as threats in the San Francisco Presidio populations but continue to threaten populations in the Oakland Hills. Population numbers also suffer in dry years because precipitation plays an important role in Presidio clarkia germination, survivorship, and flowering. Pedestrian and mountain bicycle traffic are a threat to Presidio clarkia habitat, but efforts to fence off critical habitat and create defined trails have been implemented.
The EBRPD has been working with the City of Oakland and their fire department to minimize the environmental impacts of road maintenance and fire management. In 2008, the EBRPD compiled a Serpentine Prairie Restoration Plan that began monitoring and managing the Presidio clarkia populations and habitat in Redwood Regional Park. Tree removal has proved to be the most effective management technique in reopening Presidio clarkia habitat; however, annual spring mowing is also critical to maintaining the serpentine grasslands by preventing the development of thatch. Presidio clarkia seedbank increased without active planting or seed dispersal in areas that are cleared through mowing or manual thinning. Overall, the project has been successful in maintaining Presidio clarkia population numbers, restoring habitat, and integrating public land use.
CDFW may issue permits for Presidio clarkia pursuant to CESA, and you can learn more about California laws protecting Presidio clarkia and other California native plants. Populations of Presidio clarkia occur in CDFW’s Bay Delta Region. More information is also available from the U.S. Fish and Wildlife Service Species Profile for Presidio clarkia.