Beans in Depth
In preparing the Summer 2008 Now in Season column, Laleña Dolby asked a group of farmers what they would have available for this summer. It was clear that beans would be on the list, but she was not prepared for the specificity of their answers. Confounded, she asked Anthony Boutard of Ayers Creek Farm, long known for his great variety and high quality of beans, to explain the difference between string, pole, runner, bush, wax and shell beans.
Beans: What we call “beans” belong to the family Fabaceae, with two notable exceptions. Members of the Fabaceae are known colloquially as pulses or legumes. They all bear a fruit that botanists call a “pod.” Most of the beans we eat are in the genus Phaseolus; all of these originated in the Americas. Though it is never that simple when botanical classification is mixed with colloquial terms.
Fava beans are actually a vetch, genus Vicia. The “yard-long” or “asparagus” beans are a species of edible podded field pea, genus Vigna. Mung and Adzuki beans are also the genus Vigna. To keep things confusing, most members of the genus Vigna are called “peas.” They are in a different genus from the English or French pea, which is a species of Pisum. These are all “Old World” types, and were brought to the Americas by settlers.
Fava beans (left) and adzuki beans
There are also coffee and vanilla beans. Coffee is in the family Rubiaceae. Coffee bushes bear fleshy red berries, and inside the berries are two seeds we also call beans. Vanilla beans are the fermented pod of an orchid.
String beans: These are traditional varieties that have a “string,” or tough vascular tissue, along the suture of the pod. If you break the bean and a stringy thing dangles forth, it is a string bean. If it breaks cleanly, it is a snap bean. Some beans “snap” when they are young, and develop a string as the pod matures. Others snap until they are too tough to eat. String and snap beans belong to the common bean (Phaseolus vulgaris) species. Traditionalists believe string beans are the best flavored of the beans, but they are a lot of work because they must be picked very young, or the strings must be removed with a stringer or a paring knife.
Common string bean
Runner beans: These are perennial bean plants that form a tuber and generally have a climbing habit. They are a separate species, Phaseolus coccineus, from the common green bean (P. vulgaris), which is an annual. The flowers or runners are large and showy, and they are often planted as ornamentals. Lima beans (P. lunatus) and tepary beans (P. acutifolius) are two other species of beans commonly eaten in the U.S.
Scarlet runner bean
Pole beans: These are climbing beans that can be trained up poles or twine. The beans that climb include: garden beans (snap and string, fresh shell and dry, green and wax), pole limas, and runner beans. Pole beans are sought out because of their exceptional flavor and tenderness. The Willamette Valley grew hundreds of acres of Blue Lake Pole beans; all had to be picked by hand. Today, they have been replaced by bush beans that can be machine harvested.
Blue Lake Pole bean
Fresh shell beans: These are beans that are harvested when the seed is mature, or nearly so, but not dry. The seed, not the pod, is eaten. Typically, green bean varieties do not make good fresh shell beans. Flageolet, cranberry and cannellini are examples of good fresh shell varieties. They have a tough pod and would not be welcome as green beans. All three are tasty as dry beans. There is also a middle point in the drying referred to as “demi-sec.”
Wax beans: Yellow snap or string beans that probably picked up the name “wax beans” because their color is similar to bee’s wax.
Yellow string bean
Bush bean: As the name suggests, it is a bean variety that has a bushy habit. They produce beans in a shorter time than pole beans, and the beans tend to be ready about the same time. Bush beans can be harvested by machine. The beans that are bush beans include: garden beans (snap, wax and string, fresh shell and dry, green and wax) and bush limas. The tepary beans do not climb, per se, but have a viney habit, sprawling across the ground.