Suisun thistle

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.