Cirsium altissimum (L.) Spreng.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Robust, fibrous-rooted perennial, 1–3(–4) m, openly branched when well developed; stem crisply spreading-hirsute to subglabrate, sometimes slightly tomentose in the infl; lvs large, the lower to 5 × 2 dm, broadly oblanceolate to obovate or elliptic, densely white- tomentose beneath, scabrous-hirsute to subglabrous above, merely spiny-toothed or coarsely toothed to sometimes lobed (seldom more than halfway to the midrib), the reduced ones of the infl sometimes more evidently lobed than the others; heads several or numerous on the ± leafy peduncles; invol (2–)2.5–3.5(–4) cm; middle and outer bracts tipped with a spine 2–5 mm; inner bracts merely attenuate or often with a scarious, slightly dilated and erose tip; fls mostly pink-purple; achenes 4.5–6 mm; 2n=18(20). Fields, waste places, river-bottoms, and open woods; Mass. to N.D., s. to Fla. and Tex. July–Oct. (C. iowense)