The common bean is a highly variable species. Pole snap beans 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, up to 1.5 cm long, range widely in color, and are often mottled in two or more colors.
Varieties of the pole snap beans specialized for use as green beans, selected for the succulence and flavor of their pods, are the ones usually grown in the home vegetable garden. Pod colour can be green, golden, purple, red, or streaked. Shapes range from thin fillet types to wide romano types and more common types in between. French Haricots verts (green beans) are bred for flavorful pods.