Grown as food for humans and forage for animals, as well as for soil improvement, legumes are available in dozens of varieties. They have the unusual ability to take nitrogen present in the air and "fix" it into the soil, making it available for nearby and subsequently planted crops. Edible legumes, when paired with a grain such as rice, combine to produce a protein that is nutritionally complete for humans.
Native to the Americas, peanuts (Arachis hypogaea) are known as ground nuts in other parts of the world. A true legume and not a nut, peanuts are widely grown commercially for their oil and other food products, in addition to their wide use as a snack nut. Grown in the home garden, they will produce an acceptable crop in areas with long growing seasons. Peanuts are unique in that they produce flowers above ground but the edible pods develop underground. The fertilized seed peg curves downward and penetrates the soil, which then enlarges, forming the seed-filled pod. You can plant peanuts in loose, well-drained soil, in full sun, after all danger of frost has past. Sow peanuts 1 inch deep and 6 to 8 inches apart in rows 24 to 36 inches apart. Peanuts mature 120 or more days after sowing.
A legume used primarily for soil improvement or animal forage, white clover (Trifolium repens) is a perennial clover that grows best in cool weather and fertile soils. It was previously included in lawn grass mixtures, although this is not widely practiced anymore. Plant white clover in late summer, early fall or early spring for soil improvement. Like all legumes, it improves the soil, making nitrogen available to other plants. Till white clover under, when it is about 6 inches high, incorporating it into the garden bed, where it will break down and further improve the soil.
English Garden or Edible Pod Peas
The most commonly grown legume in the home garden, English garden or edible pod peas (Pisum sativum var.) serve double duty in vegetable gardens: they produce an edible crop and improve the soil. English garden peas grow on vines that reach about 24 to 30 inches high and must be removed from the pods before eating. Edible pod peas, also called sugar snap or snow peas, grow on vines 4 to 6 feet high. They are picked while still immature and are eaten entirely, with the pod. You can plant peas in early spring, as soon as the soil can be worked. Sow them along a fence or other support structure, spacing the seeds about 2 inches apart. Keep them well-watered and cultivate to remove weeds. Garden peas will mature in about 45 days and edible podded varieties mature in 60 to 65 days. All peas love cool weather and will stop producing when hot summer weather arrives. A second crop can be grown in autumn by sowing seeds in late summer.