Peanut
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This article is about peanut, the plant. There is a separate article about Peanuts, the comic strip by Charles M. Schulz.
Peanut
Peanut leaves and freshly dug pods
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Fabales
Family: Fabaceae
Subfamily: Faboideae
Tribe: Aeschynomeneae
Genus: Arachis
Species: A. hypogaea
Binomial name
Arachis hypogaea
The Peanut (Arachis hypogaea) is a species in the pea family Fabaceae native to South America. It is an annual herbaceous plant growing to 30-50 cm tall. The leaves are alternate, pinnate with four leaflets (two opposite pairs; no terminal leaflet), each leaflet 1-7 cm long and 1-3 cm broad. The flowers are a typical peaflower in shape, 2-4 cm across, yellow with reddish veining. After pollination, the fruit develops into a legume 3-7 cm long containing 2-3 (rarely 1 or 4) seeds, which forces its way underground to mature. Although a nut in the culinary sense, in the botanical sense the fruit of the peanut is a woody, indehiscent legume or pod.
Peanuts are also known as Groundnuts (because they grow underground), Earthnuts, Goobers, Goober peas, Pindas, Pinders, Manila nuts and Monkey nuts (the last of these is often used to mean the entire pod, not just the seeds).
Contents [showhide]
1 Origins
2 Cultivation
3 Cultivars of Peanuts
3.1 Spanish Group
3.2 Runner Group
3.3 Virginia Group
3.4 Valencia Group
3.5 Tennessee Red and Tennessee White Groups
4 Uses
5 Allergies
6 U.S. Department of Agriculture Program for Peanuts
7 Trade
8 See also
9 External links
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Origins
Archaeological evidence demonstrates that the peanut was domesticated in prehistoric times in South America, where wild ancestors are still found. The plant was later spread worldwide by European traders. Cultivation in North America was popularized by African American, who brought the Kikongo word goober.
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Cultivation
Peanuts, showing legumes, one split open revealing two seeds with their brown seed coatsThe flower of the Arachis hypogaea is borne above ground and after it withers, the stalk elongates, bends down, and forces the ovary underground. When the seed is mature, the inner lining of the pods (called the seed coat) changes color from white to a reddish brown. The entire plant, including most of the roots, is removed from the soil during harvesting.
The pods begin in the orange veined, yellow petaled, pealike flowers, which are borne in axillary clusters above ground. Following self-pollination (peanuts are complete inbreeders), the flowers fade. The stalks at the bases of the ovaries, called pegs, elongate rapidly, and turn downward to bury the fruits several inches in the ground to complete their development.
The pods act in nutrient absorption. The fruits have wrinkled shells that are constricted between the two to three seeds. The mature seeds resemble other legume seeds, such as beans, but they have paper-thin seed coats, as opposed to the usual, hard legume seed coats.
Peanuts grow best in light, sandy loam soil. They require five months of warm weather, and an annual rainfall of 50-100 cm (20-40 inches) or the equivalent in irrigation water.
The pods ripen 120 to 150 days after the seeds are planted. If the crop is harvested too early, the pods will be unripe. If they are harvested late, the pods will snap off at the stalk, and will remain in the soil.
Poor storage of peanuts can lead to an infection by the mold fungus Aspergillus flavus, releasing the toxic substance aflatoxin.
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Cultivars of Peanuts
Thousands of peanut cultivars are grown, with four major Cultivar Groups being the most popular: Spanish, Runner, Virginia, and Valencia. There are also Tennessee Red and Tennessee White groups. Certain Cultivar Groups are preferred for particular uses because of differences in flavor, oil content, size, shape, and disease resistance. For many uses the different cultivars are interchangeable. Most peanuts marketed in the shell are of the Virginia type, along with some Valencias selected for large size and the attractive appearance of the shell. Spanish peanuts are used mostly for peanut candy, salted nuts, and peanut butter. Most Runners are used to make peanut butter.
The various types are distinguished by branching habit and branch length. There are numerous varieties of each type of peanut. There are two main growth forms, bunch and runner. Bunch types grow upright, while runner types grow near the ground.
Each year new cultivars of peanuts are bred and introduced somewhere in the peanut belt of the U.S. or in other countries. Introducing a new cultivar may mean change in the planting rate, adjusting the planter, harvester, dryer, cleaner, sheller, and method of marketing.
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Spanish Group
The small Spanish types are grown in South Africa, and in the southwestern and southeastern U.S. Prior to 1940, 90 percent of the peanuts grown in Georgia were Spanish types, but the trend since then has been larger seeded, higher yielding, more disease resistant cultivars. Spanish peanuts have a higher oil content than other types of