Stems and leaves of medicago sativa
, an introduced and rather variable species, may be glabrous or sparsely hairy. The ridged (approximately square in cross-section) stems grow vertically upwards, branching a few times. Leaves have lanceolate stipules at the base of the stalk, and are divided into three small leaflets, (usually) toothed along the upper margins. Leaflets may sometimes be angled upwards, held at around 45 degrees from the stalk.
The inflorescence contains between 8 and 30 flowers, usually purple, less often yellowish or white. The corolla is about twice as long as the calyx - up to half an inch. The five narrow calyx lobes are about equal in length to the calyx tube. The banner petal is the widest, and is crossed by darker lines towards the base. The two wing petals are held at a wide angle, exposing the narrower keel petals. The flower stalk is subtended by a narrow bract. The fruit is a brown, leathery pod, coiled two or three times, sparsely covered by white hairs.