Marsh vetchling

Lathyrus palustris, the marsh vetchling, is a slender climbing or trailing perennial herb in the family Fabaceae with a wide circumboreal distribution across northern Europe, temperate Asia, and much of North America. Plants arise from creeping rhizomes and reach 30-120 cm in length, with narrowly winged, weak, four-angled stems that scramble through surrounding vegetation by means of branched terminal tendrils on the leaves. Leaves are alternate and pinnately compound with 2-4 pairs of lanceolate to linear-elliptic leaflets 3-7 cm long and 5-15 mm wide, glabrous and somewhat glaucous, with leafy stipules that are narrowly arrow-shaped at the base. The inflorescence is an axillary raceme of 2-8 typical pea-flowers, each 12-20 mm long, with reddish-purple to bluish-violet standards and somewhat paler keel and wing petals. Flowering takes place from June to August. The fruit is a flat dehiscent legume 3-6 cm long containing several smooth dark seeds. The species inhabits wet meadows, fens, lakeshores, riparian thickets, sedge marshes, and damp grassy clearings, typically on moist to seasonally waterlogged neutral soils.