Slender annual, climbing or decumbent, 3-6 dm; lfls mostly 2-5 pairs, seldom more, linear-oblong to oblanceolate or narrowly elliptic, 1-2 cm; peduncles 1-3 cm, with 1 or 2(-4) light purple to white fls 3-7 mm; lowest cal-lobe linear, about equaling the tube, the upper much shorter and triangular; style minutely hairy all around near the tip; fr flat, glabrous, with (3)4(-6) seeds; 2n=14. Native of Eurasia, intr. in fields and waste places from Que. to Wis., s. to Fla. and Tex. May-Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.