Perennial herbs, 30-100 cm. Stems erect, ascending, rarely prostrate, quadrangular, glabrous or puberulent, much branched. Stipules ovate-lanceolate, base entire or with 1 or 2 denticles, apex acute; leaflets long ovate, obovate, to linear-ovate, (5-)10-25(-40) × 3-10 mm, papery, appressed pubescent abaxially, glabrous adaxially, lateral veins 8-10 pairs, base tapering, mar­gin serrulate in upper 1/3, apex rounded, mucronate with a den­ticle from midrib. Heads or racemes with 5-30 flowers, 1-2.5 cm; peduncles straight, longer than leaves; bracts equal to pedi­cels, ca. 2 mm. Corolla variable in color, white, deep blue, to dark purple; standard oblong, retuse. Ovary linear; ovules nu­merous. Legume tightly coiled in 2-4(-6) spirals, 5-9 mm in diam., center solid or nearly so, brown when ripe, veins thin and inconspicuous. Seeds 10-20, yellow or brown, ovoid, 1-2.5 mm, smooth. Fl. May-Jul, fr. Jun-Oct.