Perennials, 30-150 cm. Stems 1-several, branches ascending, glabrous to ± hirsute. Leaves minutely hispid, resin-gland-dotted; basal and proximal cauline petiolate, blades 10-25 cm, margins usually 1-2-pinnately divided into linear or oblong segments; mid and distal cauline smaller, entire or once dissected. Heads borne singly or few in open cymiform arrays, pedunculate. Involucres ovoid to hemispheric, becoming campanulate, 15-25 mm. Phyllaries: bodies dark green, ovate (outer) to oblong-lanceolate (inner), glabrous or finely arachnoid, margins and erect appendages black, ± fringed distally with slender teeth, inner phyllaries with brownish scarious, expanded, erose dissected appendages. Florets many; corollas reddish purple (white), those of sterile florets 35-40 mm, often conspicuously enlarged, those of fertile florets 20-25 mm. Cypselae brown, 4.5-5 mm, puberulent; pappi of many unequal stiff bristles, white, 4-5 mm. 2n = 20 (Russia), 40. Flowering summer (Jun-Sep). Disturbed sites, pastures, sparingly escaped from cultivation, probably not persisting in all areas where reported; 50-1800 m; introduced; B.C., N.B., Ont., Que.; Conn., Idaho, Iowa, Ky., Maine, Mont., N.H., N.J., N.Y., N.Dak., Ohio, Pa., Utah, Wyo.; Europe.
Taprooted perennial 3-15 dm, the caudex clothed with the long, chaffy-fibrous, persistent lf-bases of former years; herbage hirsute or subglabrous, and slightly arachnoid when young; lvs deeply pinnatifid, or the basal ones sometimes merely toothed; heads few or solitary, naked pedunculate, hemispheric or ovoid; invol 16-25 mm, its bracts with a conspicuous, blackish, scarious, pectinate-fringed tip; fls generally purple, the marginal ones usually enlarged; pappus 3-6 mm; 2n=20, 30, 40. Fields and waste places; native of Europe, escaped from cult. and found here and there in the n. part of our range. June-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.