Rhizomatous, 1-12 dm, the stems glabrous except for some puberulence beneath the heads; lvs chiefly cauline, veiny, with several pairs of evident divergent primary lateral veins, ±serrate, sessile or nearly so, scabrous above, hairy or occasionally glabrous beneath, elliptic to oblong or lance-oblong, 3-10 נ0.6-2.5(-3) cm; heads several in a short and broad, sparsely leafy-bracteate, corymbiform infl, or seldom solitary; invol 6-11 mm, its relatively broad, firm bracts ±imbricate, rounded to acute, puberulent or more often glabrous except for the ciliate or fimbriate margins, often squarrose-tipped, the green tip often ill-defined or wanting; rays 15-40, violet, 8-15 mm; achenes glabrous; 2n=18. Bogs, streambanks, and other moist places; Lab. and Nf. to Md., Va., W.Va., and Ky.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
