Slender annual to 1 m, erect to ascending, often climbing; lfls 4-8 pairs, oblong to elliptic or even obovate, or sometimes linear, 1-3.5 cm; stipules half-sagittate, often sharply serrate, with a glandular spot beneath; fls mostly paired in the upper axils, subsessile, violet or purple, rarely white, 18-30 mm; cal-tube campanulate, 5-7 mm, its lobes linear-subulate, the upper 3-7 mm, the lower 4-9 mm; fr flattened, light brown, 2.5-7 cm, 4-12-seeded; 2n=12. Native of s. Europe, widely cult. in numerous races, and often escaped in our range. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.