The peanut is the seed of an annual plant that is thought to have originated in South America (Brazil or Bolivia) or China. It has been a staple of the South American diet for centuries, and was grown by the Aztecs and eaten throughout South America long before the arrival of the Spanish and the Portuguese colonists in the 15th century. Introduced by these colonists into Africa and the Philippines, it was first taken to the United States at the time of the slave trade. Toward the end of the 19th and the beginning of the 20th century, vast numbers of peanut plants were grown in North America, and in 1890 peanut butter was invented, quickly becoming just as popular as it is today. Over 90% of the world's peanuts are grown in Asia and Africa, and along with the United States, the leading peanut-producing countries are India, China, Nigeria, Argentina and Indonesia.
Although it is commonly referred to as a nut, the peanut is in fact a legume that belongs to the same family as peas and beans, and can be used in the same ways. It is also referred to as the "goober" or "goober pea"- a name derived from the word nguba, which means "peanut" in Kongo, a Bantu language spoken in Zaire, the Congo Republic, and Angola.
The peanut plant thrives in tropical and subtropical climates, but it can also grow in temperate regions. A climbing or bushlike plant that reach 30 inches in height, it is covered with small yellow flowers for 2 or 3 months of the year. The buds of these flowers open at sunrise, are fertilised during the early morning hours, and wither and die before noon. Over the next few days, the stems of the flowers grow longer and bend toward the ground, which they penetrate to a depth of 1 to 3 inches; the ends of the stems then expand and ripen underground, becoming seed-bearing pods. Usually 1 to 1 ? inches long, these veined pods contain two or three seeds and become brittle when dried. Each of oval seeds is covered with a reddish brown membrane and is made up to two thick, fleshy off-white cotyledons and a visible embryo. These cotyledons and the embryo they enclose comprise what is commonly known as the "nut," which can be eaten either plain or roasted.
Peanuts are harvested by uprooting the whole plant and removing the pods after the plant has been allowed to dry for a few days in the fields or in a drying shed. There are approximately ten different species of peanuts and a large number of varieties.