Cirsium douglasii DC.

Biennials or short-lived monocarpic perennials, 60–250 cm; taprooted. Stems 1–several, erect or ascending, densely gray-tomentose; branches few–many, ascending to spreading. Leaves: blades oblong-elliptic to obovate, 10–60 × 2–15 cm, unlobed or shallowly to deeply pinnatifid, lobes lanceolate to ovate-triangular, ascending to spreading, entire to coarsely dentate or lobed, main spines slender to stout, 2–30 mm, faces densely gray-tomentose, rarely glabrate; basal present at flowering, petiolate; principal cauline well distributed, proximal winged-petiolate, distal sessile, bases auriculate-clasping or decurrent as a spiny wing 1–3 cm; distalmost well separated, bractlike. Heads 10–many, often crowded at branch tips, collectively forming paniculiform arrays. Peduncles 0–4(–8) cm. Involucres ovoid to hemispheric, 1.5–3 cm, 2–4.5 cm diam, loosely arachnoid on phyllary margins or glabrate. Phyllaries in 6–8 series, imbricate, often with dark purple patch near tip, ovate-lanceolate (outer) to linear-lanceolate (inner), abaxial faces with linear to elliptic glutinous ridge; outer and middle appressed, entire, spines spreading, 1–9 mm; apices of inner often purple-tinged, often flexuous, flattened, spineless, scabrid. Corollas rose-purple (white or pinkish-tinged), 18–21 mm, tubes 8–9 mm, throats 5–6 mm (abruptly expanded), lobes 5–6 mm; style tips 3–4.5 mm. Cypselae dark brown to black, 5–6 mm, apical collars not differentiated; pappi 15–20 mm.

Cirsium douglasii is a species of thistle known by the common names Douglas' thistle and California swamp thistle.

It is native to the central coast and northern California ranges, foothills, and plateaus, and adjacent parts of southern Oregon and northwest Nevada. It grows in wet places in a number of types of habitat.

Cirsium douglasii là một loài thực vật có hoa trong họ Cúc. Loài này được DC. mô tả khoa học đầu tiên năm 1838.