Just this year, three small and precarious populations of California saxifrage (Saxifraga californica) have been discovered in San Francisco, having had the good fortune of reaching a recognizable state while a knowledgeable botanist happened to be in the neighborhood. First documented in San Francisco County by T.S. Brandegee (1891) and then by Peter Raven in the 1950s (Howell, et al. 1958), California saxifrage has not been documented in the City since. A search of the Consortium of California Herbaria database1 doesn’t yield a single accessioned specimen of California saxifrage from San Francisco County, despite an abundance of suitable or formerly suitable habitat. So what is California saxifrage, you ask?
The saxifrages might be more familiar to those of you from the northeastern United States, as this group is most common in temperate regions of East Asia, Europe and North America. The saxifrage family (Saxifragaceae) has a worldwide distribution and includes some 600 species in 40 genera. Other native California members of the family include Boykinia , golden saxifrage (Chrysosplenium), alum root (Heuchera), Jepsonia, woodland star (Lithophragma), miterwort (Mitella), Tellima, piggyback plant (Tolmiea), and laceflower (Tiarella). Formerly assigned to this family are the currants and gooseberries (Ribes), which are now assigned to the Grossulariaceae.
Worldwide, there are some 400 species of Saxifraga, with about 20 species or subspecies native to California. The genus consists of mostly perennial herbs growing from a non-woody caudex2 or rhizome3 and is distinguished from other members of the family by having two or more non-showy flowers with five conspicuous sepals, ten stamens, non-fused styles, and (you’ll love this one) two ovary chambers. Leaves are roundish and not jointed to the petiole.
California saxifrage is a delightful, delicate plant that would be right in place in your rock garden. It has mostly basal leaves arising from a short erect caudex. The leaves are ovate to oblong, with slightly serrate margins, and one-half to two inches long on slightly shorter petioles. It produces succulent, greenish-red, upright flower stalks (inflorescences) that are four to twelve inches high. The five purplish sepals are soon reflexed, revealing white petals less than a quarter of an inch long. The fruits are capsules. In our area, flowering occurs from February through April.
California saxifrage has been recorded from 45 of California’s 58 counties, occurring from San Diego to Siskyou County and from the coast to the Sierra Nevada foothills and the Transverse Ranges. Its range extends south into Baja California and northward into southwest Oregon. It is restricted to moist, shady locations below 4,000 feet in elevation. As the name implies, saxifrages (Latin, saxum, rock and frango, to break) are often associated with rocky ground, occurring in rock crevices.
Past chapter president Jake Sigg reports the presence of a very small population of California saxifrage on Bayview Hill at the radio tower site, a botanical hot spot. He found a few plants there one year, but they went the way of the dodo. But in mid March of this year, while weeding nearby, Jake found a few plants at a different location clinging to existence. Early this year, during a weeding party in the remaining native grassland near the intersection of Palou Avenue and Phelps Street, Natural Areas Program (NAP) staff found a population of about two dozen plants of California saxifrage. And in late March NAP staff found several dozen plants growing on Billy Goat Hill (Castro Street and 30th Street). Chapter newsletter editor Barbara Pitschel recalls seeing the species on Bernal Hill some 35 years ago, but despite many years of work and walks there, she has never seen it again.
The existence of California saxifrage in San Francisco is not surprising; there is an abundance of highly suitable habitat, if not for the presence of so very many invasive species. These delicate moisture-loving perennials are easily squeezed out by dense grasses and forbs that not only over-top them but also dry out the soil before they can flower and set seed. The Palou-Phelps population is growing among a bed of the horribly invasive and pernicious Bermuda buttercup (Oxalis pes-caprae). The Bayview Hill population is threatened by sheep sorrel (Rumex acetosella) and annual grasses. The Billy Goat Hill population is threatened by Bermuda buttercup, perennial sweet pea (Lathyrus latifolius), English plantain (Plantago lanceolata), and annual grasses.
In her 1891 catalog of the plants of San Francisco, T.S. Brandegee reported her observations of California saxifrage as being the eastern Saxifraga virginiensis, confusing it with a widespread species from the eastern half of the United States and Canada. She recorded it at Mission Hills and Laguna Honda. Howell, et al. (1958) reported it from the Bayview Hills. On nearby San Bruno Mountain, McClintock, et al. (1990) reported California saxifrage as an occasional occupant of moist grasslands and brushy or rocky areas in Colma Canyon, Cable Ravine, Devil’s Arroyo and the vicinity of East Powerline. There is no record of California saxifrage at the Presidio and I have never found it on Yerba Buena Island, although it has been recorded on Angel Island. It has been recorded from every county surrounding San Francisco Bay.
The (re)discovery of California saxifrage at these forgotten remnants of natural habitat, isolated in a sea of housing and industry and all but given up for lost amid the invading weeds, provides continued hope that there are discoveries yet to be made and motivation for the citizens of San Francisco to fight for the preservation of these last vestiges of our natural heritage.
2 A caudex is the persistent, often woody base of a herbaceous perennial.
3 A rhizome is a horizontal underground stem or rootstock.