Yellowspine Thistle

Perennials, 30–90 cm; crown sprouts or runner roots producing adventitious buds. Stems 1–20+, erect or ascending, densely gray-tomentose with non-septate trichomes; branches 0 or few, usually in distal ¹/2, ascending. Leaves: blades oblong to narrowly elliptic, 10–30 × 2–8 cm, strongly undulate, margins coarsely dentate or shallowly to deeply pinnatifid with 8–15 pairs of lobes 0.5–2 cm, often revolute, lobes ± triangular, closely spaced, spreading, spinose-dentate and cleft into 2–5 spine-tipped divisions, main spines 5–20 mm, yellowish, abaxial faces densely white-tomentose, adaxial thinly gray-tomentose; basal usually present at flowering, winged-petiolate; principal cauline sessile, progressively reduced distally, bases ± auriculate to long-decurrent as spiny wings; distal cauline usually much reduced, less lobed. Heads 1–few, in leafy, ± corymbiform arrays. Peduncles 0–4 cm. Involucres ovoid to hemispheric or broadly campanulate, 2.5–4.5 × 2.5–4.5 cm in first-formed heads, often smaller in later ones, loosely arachnoid on phyllary margins or glabrate. Phyllaries in 5–10 series, imbricate, ovate (outer) to linear-lanceolate (inner), margins entire, abaxial faces with narrow glutinous ridge; outer and middle appressed, spines spreading, 3–12 mm; apices of inner often flexuous, expanded and flat, scabrid-margined, sometimes erose, spineless. Corollas white or pale lavender to purple, pink, or red, 25–45 mm, tubes 8–25 mm, throats 6–17 mm, lobes 6–15 mm; style tips 2–8 mm. Cypselae light brown, sometimes with lighter or darker streaks, 6–9 mm, apical collars colored like the body, narrow; pappi (white or tawny), 20–40 mm, usually noticeably shorter than corolla. 2n = 30, 31, 32, 34.

Cirsium ochrocentrum is a species of thistle known by the common name yellowspine thistle. It is native to the Great Plains of the Central United States and to the desert regions of the western United States and northern Mexico. Its range extends from eastern Oregon east to the Black Hills of South Dakota, south as far as the Mexican State of Durango.