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peanut, name for a low, annual leguminous plant (Arachis hypogaea) of the family Leguminosae (pulse family) and for its edible seeds. Native to South America and cultivated there for millenia, it is said to have been introduced to Africa by early explorers, and Africans transported as slaves brought the plant with them to North America. In the United States it has been extensively cultivated only since the late 19th cent. It is now grown in most tropical, subtropical, and temperate regions, especially in India and China (the major world producers), W Africa, and the SE United States. The peanut plant is unusual for its habit of geocarpy: when the pod starts to form, it is pushed into the ground by the elongation of its stalk and matures underground. There are two types of peanut plant—bunch nuts and vine, or trailing, nuts—named for the way the plants grow.
The seeds of the plants—peanuts, also known as goobers, pinders, earthnuts, groundnuts, and ground peas—are eaten fresh or roasted and are used in cookery and confectionery. They are ground for peanut butter, an important article of commerce, and yield an oil used for margarine, cooking oil, soap manufacture, and industrial purposes. The herbage is used for hay, the residue from oil extraction (called peanut-oil cakes) for stock feed, and the whole plant, left in the ground, as pasturage for swine. Peanut crops are usually harvested by hand except in the United States. Europe is the chief importer and processor, especially for oil manufacture. In the United States the amount of the crop converted to oil depends on the demand for whole peanuts; it is usually only 15% to 20%. Because of its numerous uses (George Washington Carver developed several hundred), high protein content, and adaptability to varying demand, the peanut is an advantageous agricultural crop.
Peanut allergy became an increasing problem in the early 21st cent., leading many parents to avoid exposing their children to peanuts. After a study reported (2015) that young children with a peanut sensitivity were more likely to develop a peanut allergy if they avoided, instead of being regularly exposed to, peanuts, the U.S. National Institute of Allergy and Infectious Diseases recommended (2017) that children begin to be exposed, with medical supervision in some cases, to foods containing peanuts by around six months of age to reduce the likelihood of peanut allergy.
Peanuts are classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Leguminosae.