They are distinguished from the many other varieties of beans in that green beans are harvested and consumed with their enclosing pods, before the bean seeds inside have fully matured. An analogous practice is the harvest and consumption of unripened pea pods, as is done with snow peas or sugar snap peas.
Historically, green bean pods contained a "string", a hard, fibrous strand running the length of one side of the pod. This string was either removed before cooking, or made swallowable by cutting the pod into short segments. Modern, commercially grown green bean varieties are "stringless" and lack strings, though heirloom varieties may retain this trait.
Green beans are eaten around the world, and are sold fresh, canned, and frozen. They can be eaten raw or steamed, boiled, stir-fried, or baked. They are commonly cooked in other dishes such as soups, stews and casseroles.
The first "stringless" bean was bred in 1894 by Calvin Keeney, called the "father of the stringless bean", while working in Le Roy, New York. Most modern green bean varieties do not have strings.
Green beans are classified by growth habit into two major groups, "bush" (or "dwarf") beans and "pole" (or "climbing") beans.
Bush beans are short plants, growing to not more than 2 feet (61 cm) in height, often without requiring supports. They generally reach maturity and produce all of their fruit in a relatively short period of time, then cease to produce. Owing to this concentrated production and ease of mechanized harvesting, bush-type beans are those most often grown on commercial farms. Bush green beans are usually cultivars of the common bean (Phaseolus vulgaris).
Pole beans have a climbing habit and produce a twisting vine, which must be supported by "poles", trellises, or other means. Pole beans may be common beans (Phaseolus vulgaris), runner beans (Phaseolus coccineus) or yardlong beans (Vigna unguiculata subsp. sesquipedalis).
Half-runner beans have both bush and pole characteristics, and are sometimes classified separately from bush and pole varieties. Their runners can be about 3-10 feet long.
Over 130 varieties (cultivars) of edible pod beans are known. Varieties specialized for use as green beans, selected for the succulence and flavor of their green pods, are the ones usually grown in the home vegetable garden, and many varieties exist. Beans with various pod colors (green, purple, red, or streaked.) are collectively known as snap beans, while green beans are exclusively green. Shapes range from thin "fillet" types to wide "romano" types and more common types in between.[further explanation needed] Yellow-podded green beans are also known as wax beans.
All of the following varieties have green pods and are Phaseolus vulgaris, unless otherwise specified: