Perennial, clover-like legume (Medicago sativa). It is widely grown primarily for hay, pasturage, and silage. It is known for its tolerance of drought, heat, and cold, and for its improvement of soil by nitrification (see nitrifying bacteria) due to bacteria associated with its roots. The plant, which grows 1–3 ft (30–90 cm) tall, develops numerous stems that arise from a much-branched crown at soil level, each bearing many three-leaved leaflets. Its long primary root—as long as 50 ft (15 m) in some plants—accounts for its unusual ability to tolerate drought. Its remarkable capacity for regeneration of dense growths of new stems and leaves following cutting makes possible as many as 13 crops of hay in one growing season. Alfalfa hay is very nutritious and palatable, high in protein, minerals, and vitamins.

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