With more narrowly winged stem and petioles, lance-linear stipules 1-3 cm, fls 13-20 mm; and fr 4-7 cm, otherwise much like no. 8 [Lathyrus latifolius L.], also occasionally escapes in our range.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.