Franciscan thistle (Cirsium andrewsii)

In keeping with our theme from the previous newsletter, the subject of this issue is another rare member of the sunflower family indigenous to our region, Franciscan thistle. Many comps (short for Compositae, alternate name of the plant family Asteraceae) have common names that include the word “thistle.” In fact, some of our most pernicious weeds are thistles, including yellow star thistle (Centaurea solstitialis), purple star thistle (Centaurea calcitrapa), Italian thistle (Carduus pycnocephalus), milk thistle (Silybum marianum), and the much dreaded cardoon or artichoke thistle (Cynara cardunculus). (By 1855, Charles Darwin was already writing of vast areas in Argentina covered with artichoke thistle, a native of the Mediterranean region.) Even some members of the genus Cirsium (C. arvense, C. vulgare) are well known pests in natural areas.

Perhaps because we associate thistles with invasiveness or because of their tendency to be unapproachable due to their spiny nature, many folks tend to avoid the thistles. Few groups pose as great a challenge to identify (or to press specimens, for that matter) as the genus Cirsium. Handling the flower heads with their numerous and very sharp phyllaries is not exactly enjoyable (more than a few swear words have escaped my lips when working with them). But, like so many of our botanical jewels, spending the time to get to know them has its rewards.

The thistle tribe (Cynareae) consists of some 35 genera found naturally on all continents except South America. They are especially evident in the Mediterranean region. In California, we boast 32 taxa belonging to 24 species. Of these, seven taxa are state- or federally-listed as endangered or threatened and another five are listed in the CNPS Inventory of Rare and Endangered Vascular Plants of California.

One rare thistle indigenous to the San Francisco Peninsula is Franciscan thistle (Cirsium andrewsii). This biennial or short-lived perennial produces numerous fleshy stems reaching up to seven feet in height. Leaves are thinly cobwebby above, becoming glabrous, gray-cobwebby to tomentose below. The species produces one to a few flower heads in loose cymes. Heads contain bright red tubular flowers from June through July.

Franciscan thistle inhabits bluffs, ravines, seeps, mixed evergreen forests, and coastal scrub habitats, sometimes on serpentine. It has been found in Marin, San Francisco, San Mateo, and Sonoma counties. In San Francisco it was recorded historically from Fort Point and east of Lake Merced. Presently, within the city, it can only be found on serpentine seeps below Battery Boutelle in the Presidio.

Franciscan thistle is on the CNPS List 4:1-1-3, indicating that it is rare but found in sufficient numbers and distributed widely enough that the potential for extinction is low at this time. The CNPS List 4 is merely a watch list, intended to encourage regular monitoring of the status of native populations. The species currently receives no formal protection under the state or federal endangered species acts nor is it regarded as a significant resource under the California Environmental Quality Act. Nonetheless, its occurrence in our little corner of the world, one that has been so heavily altered by human beings, is noteworthy. Its presence at the Presidio along with so many other botanical treasures emphasizes our need to support the National Park Service’s efforts to preserve, enhance, and restore some of our most fascinating natural plant communities.