Flower:

Round or short cylindrical cluster of 5 to 30 flowers at the end of long stalks that arise from the upper leaf axils, the cluster stalk longer than the subtending leaf stalk. Flowers are about 1/3 inch long, pea-shaped with an erect upper petal (standard) that is taller than wide and streaked with darker lines especially near the base. The 2 small lateral petals are spreading, exposing the keel between them. Flower color ranges from pale lavender to deep violet, or sometimes yellow or even white depending on the subspecies. The calyx has 5 narrow teeth about as long as the calyx tube. At the base of the short flower stalk is a narrow leaf-like bract about as long as the stalk.

Leaves and stem:

Leaves are compound in 3s, each leaflet up to 1 inch long and 1/3 inch wide, widest at or above the middle and tapering at the base. Leaflets may be sparsely hairy on the underside and have a few small teeth at the tip end. Leaf color is olive to blue-green and there is a chevron pattern of light green lines on the surface. Stems are erect to ascending, much branched, weakly 4-angled and hairless to sparsely hairy.

Fruit:

Fruit is a coiled pod with 2 to 4 spirals, up to 1/3 inch diameter, turning brown when ripe and containing up to 10 yellowish to brown seeds.

Notes:

Alfalfa is a cultivated crop that escaped and now commonly grows along roads, degraded fields and other disturbed areas. While the leaves are very similar to the also-weedy Sweet-clover (Melilotus spp.), Alfalfa flowers are rather larger and the cluster rather shorter and more compact. Minnesota recognizes 2 subspecies of Medicago sativa in the state: subsp. sativa and subsp. falcata, the latter of which has yellow flowers and pods that are merely curved and not spiraled multiple times. This is treated as a separate species, Medicago falcata, in a number of references.