The common bean, Phaseolus vulgaris, is an herbaceous annual plant domesticated independently in ancient Mesoamerica and the Andes, and now grown worldwide for its edible bean, popular both dry and as a green bean. The leaf is occasionally used as a leaf vegetable, and the straw is used for fodder. Botanically, the common bean is classified as a dicotyledon. Beans, squash and maize comprised the "Three Sisters" that provided the foundation of Native American agriculture. As a legume, beans provided the nitrogen-fixing bacteria which supplied that essential nutrient to the other two crops.