With over 18,000 known species, the legume family (Fabaceae) makes up the third largest family of flowering plants. The family includes herbs, shrubs, trees and vines. The fruit of a legume plant takes the shape of a pod. Although available in a large variety of shapes and sizes, all pods are seed-bearing and open along two seams.
According to HealthGuidance, written records indicate that ancient Egyptian and Asian societies utilized beans, peas, soybeans and alfalfa. Greek botanist Theophrastus wrote of the reinvigorating nature of legumes as a form of green manure for the soil. The cultivation of beans in Europe dates back to the 1400s. In America, explorers found indigenous tribes along the Atlantic coast growing various legumes along with corn.
Importance as Food
Legumes are considered the number two source of human food and animal forage, second only to cereal grasses. American farms produce numerous legume food crops, including beans, peas, soybeans and peanuts. Other parts of the world grow legumes including carob, honeylocust, tropical tamarind and pigeonpeas, to name a few important legume food crops.
Often referred to as "the poor man's meat," beans provide high protein content and soluble fiber. Soybeans contain isoflavones, which scientists believe reduce the risk of many chronic diseases, according to a 1999 article in "The American Journal of Clinical Nutrition."
Importance as Forage
American farms use various legumes as a source of green manure, hay, pasture forage and food. The ability of legumes to fix nitrogen into the soil places legumes at the top of rotational-type crops. Forage-type legumes include clovers, cowpeas, kudzu, soybeans and various types of field peas. An increasing number of American properties utilize legumes for erosion control and cover crops, according to HealthGuidance.
Additional Usage of Legumes
Various cultures derive gums, tannins and vegetable dyes from legumes. The second hardest type of resin comes from the Trachylobium verruosum, a leguminous tree. The popular dye indigo comes from Indigofera.
South American rainforests include many timber trees considered legumes, including the South American locust and Mora. American leguminous trees include the black locust, the honeylocust and the Kentucky coffeetree.
Legume plants have the ability to fixate atmospheric nitrogen into the soil. According to the Colorado State University Extension, bacteria found in the root nodules allow for the fixation to occur by converting atmospheric nitrogen to usable ammonia nitrogen. When legume crops are continuously grown in the same area, the bacteria, or rhizobial species, for nodulation is already in the soil. Many legume seeds come inoculated with commercial sources of rhizobia specific to the plant. Farmers and gardeners can also purchase commercial inoculants for application to the seed or directly to the soil.