Perennial herbs, (25-)40-80(-100) cm. Stems erect, quadrangular, base often purplish, glabrous or puberulent. Stipules broadly triangular-lanceolate, 5-8 mm, shallowly serrate, base subhastate; petiole slender, 2.5-3.5(-5) cm, shorter above; leaflets broadly ovate, orbicular, to broadly elliptic, (15-)20-30 × (8-)15-25 mm, papery, sparsely hairy or glabrescent abaxially, glabrous adaxially, lateral veins ca. 10 pairs, inconspicuous, base rounded to broadly cuneate, margin irregularly dentate, apex rounded or truncate. Flowers (4 or)5-8(-15) in umbels; peduncle shorter than or equal to subtending leaf, slender; bracts minute, ovate, apiculate, ca. 1 mm; pedicels 3-5 mm. Corolla yellow with purple stripes, bluish when dry, (7-)9-12(-14) mm; standard oblong-spatulate, slightly constricted at middle. Ovary linear; ovules 12-14. Legume oblong-falcate to semilunar, (10-)12-18(-24) × 5-9 mm, flat, veins crosswise long reticulate, black when ripe, dorsal suture straight, apex rounded, shortly beaked. Seeds (5-)8-12, brown, broadly ovoid, ca. 3 × 2 mm, smooth to rugose. Fl. Jun-Jul, fr. Jul-Aug.
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