Legumes belong to the Leguminosae or Fabaceae family. Characteristics of this family include seeds which develop in pods, leaflets containing multiple leaves, and a relationship through the roots with bacteria that allows the plant to utilize large amounts of nitrogen. Most plants in this family are protein-rich. There are two classes of legumes: pulse and forage. Forage legumes such as alfalfa and clovers are used as ground cover and as forage material for livestock. Pulse legumes are used for food for humans and as seeds to plant new crops. They include beans, peas, soybeans and peanuts.
Forage legumes are small-seeded plants that are primarily used as forage for livestock. Examples include clovers and alfalfa, both highly desired grazing crops. Their value was noted more than 5,000 years ago by the Chinese, who felt soybeans were one of the five most important grains in their culture. Early Romans used alfalfa as feed for chariot horses. Wherever they are grown, forage legumes improve the soil by adding organic matter and enhancing water infiltration. The number of earthworms, also indicative of good soil, increases where these crops are planted.
Beans come in three types: snap beans, which have immature pods; shell beans, which have immature seeds; and dry beans, which are mature seeds. They are easy to grow and require minimal fertilization. A moderate watering program of an inch a week is adequate. Beans in general provide the U.S. recommended daily allowance (RDA) of up to 10 percent of protein and 25 to 30 percent of fiber. Beans are an excellent source of many minerals.
There are many types of peas. Some are shelled and eaten when they are soft and young like garden or English peas. Others such as snow peas or sugar peas are eaten in the pod when it is flat, before the seeds have developed. Peas are a cooler-temperature plant. They are planted in early spring and harvested in June. Weed control is the most important aspect of growing peas as they can be easily overrun. Like beans, peas are a good source of vitamins, minerals protein and fiber.
Soybeans grow in many types of soil. They are generally planted in May and harvested before the pods turn yellow for use as a green vegetable known as edamame. For seed or dry beans, the pods and plants turn golden brown before harvesting. Soybeans are high in vitamins, minerals and protein. The Food and Drug Administration has recognized their cholesterol-lowering benefits by stating that 25 g of soy protein daily may be sufficient to reduce the risk of heart disease.
Peanut seeds or kernels are used in butters, oils and flour and eaten as roasted peanuts. There are two types of peanuts: Virginia peanuts, which produce one or two large kernels; and Spanish, which produce two to three smaller kernels. Some grow as runners and others as bunches. Unlike beans, peas and soybeans, the pods develop underground about 120 days after planting. One oz. of peanuts or 2 tbsp. of peanut butter provides 10 percent of the U.S. RDA of protein. They also provide a good source of vitamins, minerals and fiber.