Alfalfa is perennial legume with several more or less erect stems arising 30-100 cm from a long taproot. The compound ternate leaves (3 leaflets) are found on the stems. Individual leaflets are elliptic-oblanceolate in shape, 2-4 cm long, with toothed margins on the distal part of the leaflet. The terminal leaflet is stalked while the lateral pair are nearly stalkless. Individual leaflets are somewhat hairy. The leaves alternate on the stems.
The inflorescence is an ovate cluster of blue to purplish flowers about 1-4.5 cm long. The clusters are terminal or found in the leaf axils. Individual flowers range from 5-11 mm long and consist of 5 united sepals, 5 united petals, 10 stamens and one pistil. The pods are spirally coiled, ranging from 5-8 mm long with several seeds.
Alfalfa is commonly cultivated for forage and is commonly dried cured for use as hay.
Alfalfa may be found as an escaped plant along roadsides or railroads or near cultivated fields in agricultural areas.
Introduced from Europe as an agricultural plant for forage, alfalfa may be found throughout agricultural areas of Canada and the United States.