Trailing or climbing perennial to 1 m; lfls usually 5-11 pairs, linear to narrowly oblong, 1-3 cm, with few lateral veins leaving the midrib at a very narrow angle; stipules entire; racemes long-peduncled, dense, secund, equaling or exceeding the subtending lf, with 20-50 crowded blue (white) fls 8-13 mm; cal-tube oblique, gibbous at base, 2-3 mm, the upper lobes broadly triangular, 0.3-0.7 mm, the lowest linear-triangular, 1.3-2.5 mm; blade of the standard about as long as the claw; 2n=14, 28. Fields, roadsides, and meadows; native of Eurasia and possibly ne. N. Amer., widely naturalized in n. U.S. and s. Can., especially eastward, and found essentially throughout our range. June-Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.