Native Flora of San Francisco

Dunes covered with native plants at North Baker Beach in the Presidio Photo: Margo Bors

This patch of dunes is thought to have been the last known habitat of the Xerces blue butterfly. Lobos Creek is at right. Photo: Greg Gaar Collection

The city of San Francisco harbors a quite diverse and impressive local flora despite its dense population. Its remnant natural areas feature a surprising number of native plant species. At the Presidio, for example, approximately two-thirds of its indigenous flora--more than 260 native species--still remains, including 12 rare or endangered species. Though native plant communities are fragmented by buildings, roads, and tree plantations, they cover 145 acres of Presidio open space, more than 10% of its total area.

As a prominent port and military establishment during the frontier days of scientific exploration of California and the west, San Francisco attracted numerous naturalists and collectors. As a result, San Francisco became the type locality for fifty or sixty species of native plants.

Its unique mosaic of habitats and consequent diversity of native plant species prompted many to study its flora, including early explorers like Chamisso and Eschscholtz, early residents like Behr and Kellogg, and then a second wave of California botanists with greater training like Katharine Brandegee and Alice Eastwood.

Study of the flora reached a pinnacle with the assiduous work of California Academy of Sciences botanist John Thomas Howell and his young co-workers, Peter H. Raven and Peter Rubtzoff. In 1958 they published a landmark flora of San Francisco that documented the historic or present occurrence of 608 native and 447 non-native plant species. Tom Daniel, one of Howell's successors in the Academy's Botany Department, is preparing a new flora to be published sometime in the early 2000s.

In 1934 John Thomas Howell published an account of a botanical ramble to Lone Mountain and the Presidio that illustrates both the continuity and change in native plant communities. Compare the excerpt of his account from 1934 (printed below) with the botanical reminiscences of Hans Herman Behr of the 1850s and Alice Eastwood of the 1890s.

--Pete Holloran

Field Days in San Francisco

San Francisco is, in certain parts, still decked with bright bits of primal vegetation, and to an extent but rarely met with in centers where humanity becomes as densely concentrated. Although, as the years pass, the fringe of natural wildness is shorn more closely--here a boulevard, there a golfing green, and yet again a vegetable garden or a building--there still remain wild areas of sufficient extent to gladden the heart and mind of the field botanist. The marine cliffs at Land's End, the sandy downs and green serpentine in the Presidio, the red chert and clay slopes of Twin Peaks, the swales, dunes, and strand about Lake Merced, all of these carry still the same plant cover that was seen and studied by Chamisso and Eschscholtz, Bolander and Kellogg, Greene, Behr, and the Brandegees. At these places today, the student can still find plants first named from the vicinity, a number of which are narrow endemics, and most of which bear an endemic cast such as one meets in an insular flora. Although it is not possible to find in San Francisco all the plants first made known to the world from its hills and downs, it is probable that the majority can yet be located with a little search.

Two plants, long uncollected, led me afield last spring in the midst of the city. Can Amsinckia kelloggii [A. spectabilis, coast fiddleneck] still be found on the slopes of Lone Mountain, and has Allocarya diffusa [Plagiobothrys diffusus P. reticulatus var. rossianorum, San Francisco popcornflower] been exterminated by the golf course in the Presidio--these were the particular questions to be answered. The quest led first to the mount which, until a few months ago, was a conical oasis of wild vegetation in a desert of streets and houses; but now on its truncated summit stands a school and its slopes have been so graded that scarcely aught remains of the native flora. It was with a doubt-filled mind that I trod the new-made ground and brushed past alien weeds crowding the freshly opened space with an alacrity which left the more tardy natives without a foothold. Passing on to a narrow border of the original undisturbed sand beside a fill of clay, a small colony of natives caught my eye. Here the sand phacelia [Phacelia distans], the trailing croton [Croton californicus], and the dune oenothera [Camissonia cheiranthifolia?] grew and, to my great delight, a few plants of Amsinckia kelloggii. To show that the plant still grew where over sixty years before it was first collected, specimens for the Herbarium of the California Academy of Sciences were prepared as a permanent record for reference. At no other place did I find the plant on the mount; and, as I left, I wondered if the next sweep of the grader would snuff out forever this plant in its classic home.

Heartened by my find, I started for the Presidio, cutting down across the cemetery which flanks the mountain on the west. Here was change too: yawning holes of exhumed graves betokened the encroachment of the living on the city of the dead. Once in the Presidio I sought those slopes above the Marine Hospital and Mountain Lake where, it appears, Green, and no one else, collected his Allocarya in 1886 and again in 1887. Again success was mine for I found this most local species growing with Microseris bigelovii on a restricted clay flat near the summit of the ridge between the Marine Hospital and Fort Winfield Scott. A collection made, I took my way homeward down sandy slopes where low masses of Chorizanthe cuspidata [San Francisco spine flower] and Cryptantha leiocarpa were beginning to bloom and where plants of the autumn-blooming Lessingia germanorum [San Francisco lessingia] were becoming evident in opens between prostrate mats of the true Baccharis pilularis [coyote bush] and bushes of Ericameria ericoides [mock heather]. It had been a day well filled.

The desire to have again in the Herbarium of the California Academy of Sciences specimens of Cirsium amplifolium [=C. andrewsii, Franciscan thistle] took me last July to Lake Merced where the plant had been collected by Miss Eastwood before the fire of 1906 and again by Suksdorf in 1913. A diligent search along the eastern shores of the lake disclosed no extraordinary thistle, only the widespread C. edule [=C. brevistylum, Indian thistle] and C. occidentale [cobweb thistle] on open sandy slopes. For the time I had given up and had started home when I lost my trail on the floor of the narrow swale east of the southern arm of the lake and became entangled in the dense growth of willows, Californian Sweet Gale, and rank herbs. In this annoying predicament while bending every effort to force my way into the open, the desired plant was found, a single robust specimen well covered with heads of light rosy-purple flowers.

--John Thomas Howell, 1934

References:

Howell, John Thomas. 1934. Field days in San Francisco I. Leaflets of Western Botany 1:89-91.

Howell, John Thomas, Peter H. Raven, and Peter Rubtzoff. 1958. A Flora of San Francisco, California. Wasmann Journal of Biology 16, no. 1:1-157. [reprints available from the Yerba Buena chapter of the California Native Plant Society]

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