Stems usually erect, sometimes decumbent or procumbent (rooting at nodes). Leaf blades triangular to deltate or ovate, 2-7(-13) cm, bases usually cuneate to truncate, rarely subcordate, margins serrate to serrate-dentate or crenate, apices acute. Phyllaries 3.5-4 mm. Corollas blue to blue-violet or rosy-violet, (1.6-)2-2.5 mm. Cypselae 1-1.5 mm, glabrous; pappi: bristle tips not dilated. 2n = 20. Flowering (Jun-)Aug-Nov. Stream banks, lakeshores, coastal and inland sands, pine-oak woodlands, low woods, flood plains, ditches, ravines, bogs, wet slopes, pine savannas, disturbed sites, roadsides, along railroads; 50-400 m; Ont.; Ala., Ark., Del., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Mich., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va.
From Flora of Indiana (1940) by Charles C. Deam
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.
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.