Cirsium occidentale var. californicum

(A. Gray) D. J. Keil & C. E. Turner

Phytologia 73: 315. 1992.

Common names: California thistle
Basionym: Cirsium californicum A. Gray in War Department [U.S.], Pacif. Railr. Rep. 4(5): 112. 1857
Synonyms: Cirsium bernardinum (Greene) Petrak Cirsium californicum var. bernardinum (Greene) Petrak Cirsium californicum subsp. pseudoreglense Petrak
Treatment appears in FNA Volume 19. Treatment on page 139. Mentioned on page 137, 140.

Plants erect, usually 50–200 cm, thinly to densely gray-tomentose, sometimes glabrate. Leaf faces abaxially green to gray, adaxially gray. Heads in ± open clusters, short- to long-pedunculate, elevated well above proximal leaves. Involucres usually about as wide as long, 1.5–5 cm, subglabrous to densely arachnoid. Phyllaries usually imbricate, mid apices appressed to loosely spreading or ascending, sometimes twisted, usually less than 1 cm (but sometimes much longer), 1–3 mm. Corollas white to light purple or rose, 18–35 mm. 2n = 28, 29, 30 (as C. californicum).

Phenology: Flowering spring–summer (Apr–Aug).
Habitat: Pine-oak woodlands, riparian woodlands, chaparral, openings in mixed evergreen forests, roadsides
Elevation: 100–2200 m


Variety californicum occurs in both coastal and interior mountains of California from the northern South Coast Range and the northern Sierra Nevada to the mountains of southwestern California. Considerable variation exists in head size, corolla color, and in length and display of phyllary appendages. In several areas of its range, the predominantly white- to light purple-flowered var. californicum occurs with red-flowered var. venustum. These plants are highly interfertile (H. Wells 1983; D. J. Keil and C. E. Turner 1992). Introgressive hybridization among them has resulted in a variety of emergent phenotypes and may have contributed to the variation within var. californicum.

Selected References


Lower Taxa

David J. Keil +
(A. Gray) D. J. Keil & C. E. Turner +
Cirsium californicum +
California thistle +
100–2200 m +
Pine-oak woodlands, riparian woodlands, chaparral, openings in mixed evergreen forests, roadsides +
Flowering spring–summer (Apr–Aug). +
Illustrated +  and Endemic +
Cirsium bernardinum +, Cirsium californicum var. bernardinum +  and Cirsium californicum subsp. pseudoreglense +
Cirsium occidentale var. californicum +
Cirsium occidentale +
variety +