Slender annual, climbing or decumbent, 3-6 dm; lfls usually 6-8 pairs, seldom fewer, linear to narrowly elliptic, 5-15 mm; peduncles 1-3 cm, with 3-8 whitish fls 3-4 mm; cal-lobes subulate, subequal, 1-1.5 mm, about equaling the tube; style not hairy, only the capitate stigma papillate; fr flattened, hirsute, 6-10 mm, normally 2-seeded; 2n=14. Native of Europe, intr. in fields, roadsides, and waste places throughout most of the U.S. and s. Can. May-Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.