12. Lathyrus quinquenervius (Miquel) Litvinov in Komarov & Alissova-Klobukova, Opred. Rast. Dal’nevost. Kraia. 2: 683. 1932.
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.