Rhizomatous perennial often forming large patches. Stems branched above, with multicellular eglandular and fine cobwebby hairs below, becoming glabrous above, (20)-40-100-(150) cm tall, ribbed, not winged or sometimes with a spiny wing 0-1-(2) cm long decurrent from lf bases. Lvs lanceolate, pinnatifid, green above, pale beneath, (2)-4-15 × 1-5 cm, glabrous or with cobwebby hairs; lobes deltoid to lanceolate; prickles pale, 5-10 mm long. Capitula narrowly ovoid to cylindric at flowering, erect, 1.5-2-(2.5) × 0.7-1.5-(2) cm, in cymes or cymose panicles; peduncles 5-40 mm long. Outer involucral bracts lanceolate, cobwebby-ciliate; apex acuminate, with weak spine 1-(2) mm long, suberect. Inner involucral bracts linear, ciliate; apex acute, not spinous, erect. Corolla usually pale purple or mauve, sometimes white, 12-18 mm long; lobes c. 3 mm long. Style slightly exserted beyond corolla lobes. Achenes pale, cylindric, 3-4 × 1-1.5 mm; pappus 20-25 mm long, shorter in ♂; cilia on pappus bristles 2-3 mm long.