Heads usually 2.5-3 cm. Cypselae oblong, ca. 5 mm. 2n = 32. Flowering spring-summer (May-Sep). Tidal marshes; of conservation concern; 0-5 m; Calif. Suisun thistle is known only from the Suisun Marsh (Solano County) in the Sacramento River delta.
Variety hydrophilum is listed by the U.S. Fish and Wildlife Service as endangered.
This project made possible by National Science Foundation Award 1410069