Prostrate, ascending or erect herb, arising from a perennial tuberous rootstock; rootstock to 13 × 9 cm, ellipsoid. Stems annual, branched, undulate or zigzag, laterally flattened, ribbed, glabrous or with sparse spreading hairs on the ribs. Leaves 1-foliolate; leaflet 4–23 × 1.4–4 cm, narrowly elliptic, lanceolate, acute or rarely rounded and mucronulate at the apex, base cuneate, glabrous or pubescent on both surfaces, 3-veined from the base or very shortly above it to the apex, the tertiary venation quite conspicuous; petiole 3–8 mm long; stipules 8–13 × 3–5 mm, lanceolate, ciliate, striate, persistent; stipels minute. Flowers axillary, solitary, in pairs or in 3–8-flowered fascicles; pedicels 5–45 mm long, glabrous or sparsely pilose; bracts absent; bracteoles minute, linear. Calyx sparsely pubescent or glabrous; tube 3 mm long; lower lobes 1.5–3 mm long, triangular, upper pair almost or completely fused. Standard pale purple or lilac, usually drying yellowish-brown, 11–12 × 12 mm, almost round; wings and keel paler. Ovary 5–7 mm long, linear-oblong, compressed, densely pubescent; style 3–4 mm long, stigma minute, terminal, capitate, penicillate. Pods 4.5–7 cm × 5–10 mm, oblanceolate, glabrous or pubescent on the surfaces, margins sparsely to densely pubescent. Seeds unknown.
