Flower:

Raceme of 10 to 20 pea-shaped flowers on a finely hairy stem arising from a leaf axil, the flower stem shorter than that of the attending compound leaf. Flowers are ½ to ¾ inch long and about 3/8 inch wide, the upper lip (standard) flaring out on the sides, richly lavender/pink with distinct darker veination. The lower lateral wing petals are pale pink to nearly white and enclose the slightly pinker keel underneath. The calyx holding the flower is attached to a short stalk, both can be smooth or covered with fine hairs.

Leaves and stem:

Leaves are compound with 4 to 7 leaflet pairs and a branched tendril at the tip. Leaflets are oval to oblong-elliptic, rounded at both ends, and can also be finely hairy or nearly smooth.

A pair of narrow leafy appendages (stipules) attend the leaves at the axil, the upper portion longer than the lower and pointed at both ends, generally shaped like half of an arrowhead. Stems are distinctly 4-angled, finely hairy to smooth, with multiple stems arising from rhizomatous root system.

Fruit:

Fruit is a smooth flat pod, 1 to 3 inches long by ¼ inch wide.

Notes:

Veiny pea is widely distributed throughout Minnesota and can readily be distinguished from the many other purple/pink flowered pea-like species by the strongly bi-colored blooms, distinct veination on the upper hood or standard, and the angled stem. Marsh Vetchling (Lathyrus palustris) has similar flowers but can be distinguished by its winged stem, fewer flowers per cluster, and fewer leaflets per compound leaf. Beach Pea (Lathyrus japonicus) also has nearly identical flowers but can be separated by its low, dense colonial growth form and very large stipules. L. japonicus is also restricted to the north eastern third of Minnesota and is most common along the north shore of Lake Superior. I've grown Veiny Pea in the home garden and the only problem, if it's a problem at all, is the rhizomatous roots creep out through the bed, diminishing in the center creating kind of a thin wall of vines migrating out. But this species is not very aggressive and the growth density does not heavily compete with other garden species. There are multiple variations of L. venosus and most references do not consider them separate species, but synomyms of a single species. The DNR, however, lists the species in Minnesota as var. intonsus.