Peanut, an annual plant of the legume family. Its edible seeds also are called peanuts. The plant differs from other leguminous plants by producing its pods underground. Botanically, the peanut is not a true nut, but is related to the pea. Peanuts are also called goobers, goober peas, groundnuts, earthnuts, monkey-nuts, and pinders. They are native to South America, but are cultivated in many parts of the world.
Peanuts are very nutritious, and are used principally as food for humans and livestock. They are rich in protein, niacin, and iron. They contain small amounts of thiamin, riboflavin, and calcium.
In the United States, about one-half of the peanuts threshed from the plants are used to make peanut butter. Peanut butter is made by roasting, blanching (removing the seed coats, or skins), and grinding the peanuts. To improve the flavor or texture, such ingredients as salt, partially hydrogenated vegetable oil, and corn syrup or honey are usually added. Peanuts are also eaten as snacks, usually roasted and salted, either in the shell or without the shell. They are also eaten in candy bars, peanut brittle, and baked goods.
The whole plant, including seeds, is often used as livestock feed. Plants from which the seeds have been harvested are fed to livestock as hay. Peanut cake, a concentrated food made from seeds that have been crushed to extract oil, is also fed to livestock. The oil is used for cooking.
Peanuts and peanut oil are used in a number of products. These include certain types of margarine, cheese, flour, ice cream, and milk, and various kinds of paint, paper, shampoo, shaving cream, and soap.
Two general types of peanut plants are grown commercially. Bunch peanuts are about two feet (60 cm) high. The vinelike runner peanuts grow upright about one foot (30 cm), and have branches two feet (60 cm) long that lie on the ground. Both types of plants have thick, hairy stems from which grow compound, oval leaves and small, yellow flowers.
The flowers are produced near the ground on bunch plants, and along the runners of the vinelike types. The plants are in bloom for about three months. The flowers are selffertilizing. About one week after fertilization, the flower produces a peg, or budding ovary. The peg grows on a vine that eventually reaches the ground. The peg enters the soil and the pod grows from its tip. The pod, tough and fibrous, is one to two inches (2.5 to 5 cm) long when mature. In most commercial varieties, each pod encloses two, sometimes three, seeds. The seeds vary to some extent in size according to variety, and may be round or oval. The seed coat is usually reddish or purple.
Peanuts are grown in tropical and subtropical climates. They will grow in almost any kind of soil, but thrive best in light, loamy soils with good drainage. They are planted in late spring in rows three feet (90 cm) apart. Four or five months later, the plants are uprooted and inverted, allowing the pods to dry in the field. After drying, the pods are separated from the plants by hand or by a threshing machine.
Several varieties of peanuts are grown in the United States. Virginia varieties, grown in Virginia and the Carolinas, produce large peanuts that are sold as snacks. Runner varieties, grown mainly in Georgia, Florida, and Alabama, produce medium-size peanuts that are used in confections and in making peanut butter and oil. Spanish varieties, grown in Texas and Oklahoma, have small kernels that are used in confections and sold as snacks.
Botanists believe that the peanut was first cultivated in South America more than 3,500 years ago. After Europeans discovered South America, peanuts were introduced into the Old World. The slave trade brought peanuts from Africa to North America in the 17th century. Peanuts were first commercially grown in South Carolina. After the Civil War, peanut cultivation spread to other areas in the South. George Washington Carver, a black botanist, developed more than 300 uses for peanuts.
The common commercial varieties of peanuts are members of one species. Aruchis hypogaea, of the family Leguminosae.