Red star-thistle

Centaurea calcitrapa

nnual or biennial to 1 m high; stem much-branched, striate; stems and leaves with coarse septate hairs.

Basal leaves oblanceolate, deeply pinnatisect with toothed lanceolate lobes, to 20 cm long; lower cauline leaves lanceolate and pinnatifid to lyrate, to 2–8 cm long, 1–3 cm wide, dark green; upper leaves entire, narrow-lanceolate to linear, 2–4 mm wide.

Heads solitary, ovoid-cylindrical, 6–10 mm diam.; involucral bracts ovate, with straw-coloured appendages and a spreading terminal spine, 10–30 mm long; 1–3 pairs of basal spines, 3–4 mm long. Florets pale purple or pink, outer erect; corolla glandular.

Achenes c. 3 mm long, glabrous; pappus absent.

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