The Birds and the Bees with a little History...
Medicago sativa is an angiosperm and has distinct reproduction. Angiosperms use flowers to attract pollinators and fruit to protect the seeds and to attract animals to disperse the seeds. Another characteristic that is unique to angiosperms is the use of double fertilization. Alfalfa is highly specialized when it comes to pollination. The flowers on alfalfa must be pollinated specifically by bees.
Though no one knows for sure, alfalfa is believed to have originated in central Asia and the Middle East. The earliest definite record was when alfalfa was introduced to Greece around 490 B.C.E. When the Spanish traveled to the Americas, they brought Alfalfa with and introduced it to Mexico and Peru. It spread throughout Central and South America, and also to Southwestern United States. When the New World was beginning to be colonized, settlers brought over alfalfa, but the soil was too acidic along the Atlantic Coast. It was not until 1850 that alfalfa became widely grown in the United States.