Medicago sativa subsp. ambigua(Trautv.) Tutin
Medicago sativa subsp. microcarpaUrban
Medicago sativa subsp. sativaL.
Medicago sativa subsp. varia(T. Martyn) Arcang.

Alfalfa (Medicago sativa), also known as Lucerne, Purple Medic and Trefoil (from Spanish Alfalfa, ultimately Arabic: البرسيم الحجازي; al-fasfasa), is a perennial flowering plant cultivated as an important forage crop. In the UK, where it is not all that widely grown, it tends to be known as lucerne.

Alfalfa is one of the most important legumes used in agriculture. The US is the largest alfalfa producer in the world. The leading alfalfa growing states (within the U.S.A.) are California, South Dakota, and Wisconsin. The upper Midwestern states account for about 50% of US production, the North eastern states 10%, and western states 40% of US production, the latter mostly under irrigation. Alfalfa is not very important in the Southeastern states. However, alfalfa has a wide range of adaptation and can be grown from very cold northern plains to high mountain valleys, from rich temperate agricultural regions to Mediterranean climates and searing hot deserts.