Description from Flora of China
Vicia quinquenervia Miquel, Ann. Mus. Bot. Lugduno-Batavi 3: 50. 1867.
Herbs perennial, 20-80 cm tall. Stem erect or clambering over surrounding vegetation, rarely branched, winged. Leaves with simple tendril; stipules linear, with reflexed basal spur, often falcate, 7-23 × 0.2-2 mm; leaflets 1- or 2(or 3)-paired, elliptic-lanceolate or linear-lanceolate, 35-80 × 5-8 mm, pubescent, with 5 stiff, prominent parallel veins, rigid when dry. Raceme 5-8-flowered. Calyx campanulate, pubescent; longest tooth equaling tube. Corolla purple-blue or purple, sometimes with white wings and keel, (12-)15-20 mm; standard orbicular, with claw; wings narrowly obovate, auriculate at base. Ovary densely hairy. Legume linear, 3-5 cm. Fl. May-Jul, fr. Aug-Sep.
This species is often confused with Lathyrus palustris but can be distinguished by the five strong, parallel veins in long, slender leaflets. The linear, acute stipules with a reflexed basal spur, the strong wings on the stems, and the simple tendrils also aid in identification.
Herbarium specimens are often mislabeled as Lathyrus palustris var. linearifolius.
Forests, hill slopes, roadsides; below 2500 m. Gansu, Hebei, Heilongjiang, Henan, Hubei, Jiangsu, Jilin, Nei Mongol, Qinghai, Shandong, Shanxi, Sichuan [Japan, Korea, Russia].