Annual or perennial, slender, twinner and pubescent young branches; leaves stipulate, stipelate, 3-foliolate, leaflets obovate, rhomboid or ovate, elliptic, membranous, glabrescent above, lustrous with fine grey silky pubescence beneath, lateral leaflets obliquely acute or acuminate; racemes drooping on short peduncles, 3-30 flowered, rachis finely silky, bracteoles smaller, lanceolate; flowers large, showy, usually purple; calyx campanulate, 5 toothed with a few pungent bristles; corolla purple, much exserted, standard slightly exceeds the wings but not longer than the rostrate keel; stamens diadelphous, anthers dimorphous; ovary sessile, many ovuled; style incurved, beardless; stigma capitate; pod 'S' shaped, densely clothed with grey to brown, stinging, needle like hairs, turgid, 5-6 seeded.