Rhizomatous; stems 3-9 dm, puberulent; lvs opposite, petiolate, crenate or crenate-serrate, deltoid-ovate, sometimes narrowly so, 3-10 נ2-5 cm, trinerved or triplinerved, sparsely appressed-hairy or subglabrous, often atomiferous-glandular; invol 3-5 mm, its bracts narrow, firm, long-pointed, ±imbricate; receptacle conic; fls 35-70 per head, bright blue or violet (rarely reddish-purple), often purplish when dry; pappus scanty; 2n=20. Woods, streambanks, meadows, and fields; N.Y. to Ill. and Kans., s. to Fla., Tex., and W.I. July-Oct. (Conoclinium c.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.