alfalfa is the American and more usual name of a leguminous plant, Medicago sativa, which is often called lucerne in Britain. Apparently a native of Media (Iran), from which comes its generic scientific name, it was said by Pliny to have been introduced to Europe in the course of the invasion of Greece by the Persian Emperor Darius in 491 bc. Laufer (1919) states that it was introduced to China as early as the 2nd century bc.
Alfalfa is now grown worldwide in warm temperate (and cool subtropical) regions, especially in the USA, the Russian Federation, and Argentina. Its main uses are as a forage crop for feeding cattle and as a green manure.