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.
Rather infrequent in the southern half of the state. My only specimen from northern Indiana was one which I found on the moist, north bank of Tippecanoe Lake, in Kosciusko County. It was in a habitat which suggested it was native although it might have been seeded there from one of the cottages on the lake, the nearest one being about 150 feet to the east. It prefers a moist, hard, clay soil and is found in roadside ditches and moist places along streams. This species is frequently cultivated and it is possible that some of our roadside plants are escapes.