The common bean, Phaseolus vulgaris, indigenous to the Americas, 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 common bean is a highly variable species. Bush varieties form erect bushes 20-60 cm tall, while pole or running varieties form vines 2-3 m long. All varieties bear alternate, green or purple leaves, divided into three oval, smooth-edged leaflets, each 6-15 cm long and 3-11 cm wide. The white, pink, or purple flowers are about 1 cm long, and give way to pods 8-20 cm long, 1-1.5 cm wide, green, yellow, black or purple in color, each containing 4-6 beans. The beans are smooth, plump, kidney-shaped, upto 1.5 cm long, range widely in color, and are often mottled in two or more colors.
Green common beans are also called string beans, stringless beans (depending on whether the pod has a tough, fibrous "string" running along its length), or snap beans. Compared to the dry beans, they provide less starch and protein, and more vitamin A, vitamin C, and calcium.The green beans are often steamed, stir-fried, or baked in casseroles.