山黧豆 shan li dou

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.

Forests, hill slopes, roadsides; below 2500 m. Gansu, Hebei, Hei­longjiang, Henan, Hubei, Jiangsu, Jilin, Nei Mongol, Qinghai, Shan­dong, Shanxi, Sichuan [Japan, Korea, Russia].

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.