The species is endemic to limited regions within northern and central California, at elevations not exceeding 750 metres (2,460 ft).

There are three recognized varieties of this species: All the taxa within Cirsium fontinale have erect stems with leaves very strongly wavy margins.

Inflorescences are characterized by prickly heads more or less grouped in a panicle-like cluster, closely subtended by the higher leaves.

Anther bases are sharply sagittate, with oblong tips; the ends of the styles manifest a somewhat swollen node, with a cylindrical superior appendage.

The smooth brownish fruits are four to five millimeters in diameter, but distinctly ovoid; many pappus bristles are exhibited.

campylon, the Mount Hamilton thistle, is uncommon, but occurs in widely distributed locations in Santa Clara, Alameda and Stanislaus County, in the southeastern San Francisco Bay Area.

[3][4][5] Elevations of this variety are from 300–750 metres (980–2,460 ft) in the southern Santa Clara Valley and the Diablo Range, including Mount Hamilton.

As with the other species varieties, the Mount Hamilton thistle prefers moist areas on serpentine soil slopes including seeps, riparian stream environments, and other wetlands.

campylon compared to other varieties of this species manifest first in a green stem which has a maximum height of 2 metres (6.6 ft).

campylon are strongly and permanently nodding; moreover, its outer phyllaries present a greenish color and have a length of 20 to 30 millimeters.

[7] However at two of these locations, in or near Edgewood County Park, plants have not been observed for several years, and these populations are presumed extinct.

fontinale was found in the 1980s on serpentine soil along the east side of Upper Crystal Springs Reservoir.