San Francisco owl’s-clover is another of San Francisco’s rare beauties in extreme danger of being lost from our city forever. This annual herb in the figwort family (Scrophulariaceae)produces openly branched, straw-colored, erect stems four to twelve inches high. It is readily recognized by its creamy-white flowers, with long slender tubes and inflated lower lips with three prominent sacs, arranged in compact, dense in florescences one-half to two inches high. Blooming generally occurs April through May, but can start as early as March. The leaves are one half to one-and-a-half inches long and deeply divided into five to nine linear lobes. Flower bracts differ only gradually from the leaves, being smaller and with three to seven lobes. Fruit capsules,less than a quarter inch long, contain 20 to 30 dark brown seeds.

San Francisco owl’s-clove rwas first described in 1835 by the outstanding English taxonomist George Bentham,probably from specimens collected by David Douglas, who is credited with collecting more than 500 California plant species for the Royal Horticultural Society. Formerly called Orthocarpus floribundus, its nomenclature was revised to Triphysaria floribunda by Chuang and Heckard in 1991.

San Francisco owl’s-clover is a very narrow endemic, restricted to open places in coastal prairies and occurring on both serpentine and clay soils. It is most abundant near Drake’s Bay and the Point Reyes lighthouse in Marin County, the northern most occurrences of the species. In San Mateo County, the California Natural Diversity Data Base lists historic populations on Point San Bruno in South San Francisco and on San Bruno Mountain, although the species hasn’t been seen at either of these locations since the mid 1960s. Other historical San Mateo County locations listed in Thomas’ Flora of the Santa Cruz Mountains of California (1961) include Colma, Burlingame, San Mateo, Seal Cove, San Andreas Lake, and Belmont, but none of these populations are believed extant.

In San Francisco County, only a single population of San Francisco owl’s-clover is still present. Occurring on serpentine, this stand is located in the Presidio near the last naturally-occurring individual of Raven’s manzanita (see September 1995 Yerba Buena News). In 1982, the population size was estimated at around 1,000 plants. Only 22 were counted in 1985 and nine were counted in 1993 and 1995.

The Natural Diversity Data Base lists other historical populations of San Francisco owl’s-clover at Potrero Hill and near Lake Merced. Very little habitat remains for the species on Potrero Hill and it has not been seen there since 1881. It was last seen near Lake Merced in 1907. The flora of San Francisco by Howell, Raven and Rubtzoff, lists other historical locations as above Fort Point, Bakers Beach, Bayview Hills, and San Miguel Hills.Due to the abundance of San Francisco owl’s-clover on the Point Reyes Peninsula, the species does not receive any official federal protection under the Endangered Species Act. The United States Fish and Wildlife Service (USFWS) presently lists it as a Category 2 Candidate for federal listing. This designation if given to taxa for which existing information indicates that a listing may be warranted, but sufficient biological data to support a proposed ruling are lacking. Given the USFWS’s current moratorium on new listings, a proposal to change the status of San Francisco owl’s-clover is not likely any time soon.

Similarly, San Francisco owl’s-clover does not have any official status as a threatened or endangered species under the California Endangered Species Act. However, the California Department of Fish and Game (CDFG) does consider it a special plant species and has assigned it a global rank of G-2 (6-20 estimated occurrences or 1,000-3,000 individuals or 2,000-10,000 acres) and a state rank of S2.2 (same population status as G-2 but considered threatened).

Similarly, San Francisco owl’s-clover does not have any official status as a threatened or endangered species under the California Endangered Species Act. However, the California Department of Fish and Game does consider it a special plant and has assigned it a global rank of G-2 (6-20 estimated occurrences, or 1,000-3,000 individuals or 2,000-10,000 acres) and a state rank of S2.2 (same population status as G-2 but considered threatened).

Perhaps the most accurate representation of the actual rarity and threatened status of San Francisco owl’s-clover is provided by the CNPS’s Inventory of Rare and Endangered Vascular Plants of California, which lists the species as a 1B:2-2-3. This designation indicates that the species is rare and endangered, has an occurrence confined to several populations or to one extended population, is endangered in a portion of its range, and is endemic to California. Taking into account that only a single, tiny population of San Francisco owl’s-clover remains south of Marin County, and considering its former extent and loss of habitat in San Francisco and San Mateo counties,the species may well be deserving of official state and/or federal status.Without a concerted effort to preserve the San Francisco population, the species could easily be extirpated from this county as well.

Current threats to San Francisco owl’s-clover in Marin County include grazing and trampling by cattle. It’s too early to tell what effect the recent Point Reyes fire and efforts to fight it might have had on the species, although it is expected to continue to thrive as long as it hasn’t been too heavily impacted by the cutting of fire breaks, road grading, or equipment operation during efforts to control the blaze. In San Francisco, the former extent of the species has been most significantly impacted by a loss of habitat as a result of urban expansion. The last natural San Francisco population is threatened by human trampling, rodents, exotic plant invasion and shading from nearby Monterey pines (Pinus radiata) and Monterey cypress (Cupressus macrocarpa), although most of these threats have been reduced by management of the site.

Although the National Park Service has yet to implement a species-specific program to preserve San Francisco’s last population of Triphysaria floribunda, the site is being carefully monitored. Efforts to protect the site have included removal of invasive exotic species such as German ivy (Senecio mikanioides)and ice plant (Carpobrotus edulis),removal of Monterey pines, and restricting human trampling by use of fencing.Future restoration efforts by the Park Service will include conducting seed germination trials using seed of the more abundant Point Reyes populations. If germination rates and transplanting prove successful, seed would be collected from the San Francisco plants and raised with the hopes of increasing available seed for reintroduction onsite.

To find out what you can do to help preserve native habitats on the Presidio, check out the “Habitat Restoration” page of this website. Get involved and have fun too!