Erect or ascending, glabrous perennial, 30-90 cm, with alternate trifoliate leaves ; leaflets, 30 mm, narrowly obovate, toothed in upper third with a mucronate tip; stipules linear-lanceolate, usually serrate. Numerous stems originating from crown buds ; as the stems develop, axillary buds formed in lower leaf axils produce further stems which build up a crown of basal buds at their base. Crown is the main source of stems produced after defoliation ; axillary buds above ground develop into branches. Deep-rooted, 2-4 m, or more in deep, well-drained soils. About 60-70% of total root mass is in the upper l5 cm of soil profile. Inflorescences are compact racemes up to 40 mm, borne in axils of upper leaves ; purple florets, 8 mm, typically papilionacious. Cross-pollinated by various species of bee. Seed pods spirally coiled, glabrous or pubescent ; pods turn from green to brown as they mature, and contain 2-5 kidney-shaped, yellow or brown seeds. A proportion of the seeds are hard, probably inversely related to temperature during seed set.