Erect, weedy annual, 1.5-6 dm, sparingly branched, very viscid-hairy throughout; lvs long-petioled, lanceolate to ovate, 2-5 cm; fls solitary or paired in the upper axils, short-pedicellate; hypanthium nearly 1 cm; pet red-purple, clawed, the upper 2 the largest, ca 8 mm; 2n=12. Dry soil; N.H. to n. Ill. and Kans., s. to Ga. and La., commoner southward. July-Sept. (C. petiolata, a preoccupied name)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.