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FNA | Family List | FNA Vol. 19, 20 and 21 | Asteraceae | Cirsium

40d. Cirsium occidentale (Nuttall) Jepson var. californicum (A. Gray) D. J. Keil & C. E. Turner, Phytologia. 73: 315. 1992.

California thistle

Cirsium californicum A. Gray in War Department [U.S.], Pacif. Railr. Rep. 4(5): 112. 1857; C. bernardinum (Greene) Petrak; C. californicum var. bernardinum (Greene) Petrak; C. californicum subsp. pseudoreglense Petrak

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).

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

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.


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