Thought to be one of the oldest crops cultivated by humans, alfalfa was first discovered and grown in the deserts of northern Iran. The leafy, palatable plant was introduced to the continental United States during the gold rush and the cultivation of it has since spread across the country. Although the rugged alfalfa crop grows best in fertile, well-drained soils that receive plenty of rainfall, breeding efforts have developed varieties that are winter hardy, pest resistant and more heat and drought tolerant