Peanut

Appearance

The flowers are a typical peaflower in shape, 2 to 4 cm across, yellow with reddish veining. ''Hypogaea'' means "under the earth", after pollination, the flower stalk elongates causing it to bend until the ovary touches the ground. Continued stalk growth then pushes the ovary underground where the mature fruit develops into a legume pod, the peanut – a classical example of geocarpy. Pods are 3 to 7 cm long, containing 1 to 4 seeds.

Naming

Peanuts are known by many other local names such as earthnuts, ground nuts, goober peas, monkey nuts, pygmy nuts and pig nuts. Despite its name and appearance, the peanut is not a nut, but rather a legume.

Evolution

The domesticated peanut is an amphidiploid or allotetraploid, meaning that it has two sets of chromosomes from two different species, thought to be ''A. duranensis'' and ''A. ipaensis''. These likely combined in the wild to form the tetraploid species ''A. monticola'', which gave rise to the domesticated peanut. This domestication might have taken place in Paraguay or Bolivia, where the wildest strains grow today. Many pre-Columbian cultures, such as the Moche, depicted peanuts in their art.

Archeologists have dated the oldest specimens to about 7,600 years, found in Peru. Cultivation spread as far as Mesoamerica where the Spanish conquistadors found the ''tlalcacahuatl'' being offered for sale in the marketplace of Tenochtitlan . The plant was later spread worldwide by European traders.

Although the peanut was mainly a garden crop for much of the colonial period of North America, it was mostly utilized as animal feed stock until the 1930s. In the United States, a U.S. Department of Agriculture program to encourage agricultural production and human consumption of peanuts was instituted in the late 19th and early 20th centuries. George Washington Carver is well known for his participation in that program in which he developed hundreds of recipes for peanuts.

Uses

Peanuts can be used like other legumes and grains to make a lactose-free milk-like beverage, peanut milk. Peanut plant tops are used for hay.

Low grade or culled peanuts not suitable for the edible market are used in the production of peanut oil. The protein cake residue from oil processing is used as an animal feed and as a soil fertilizer. Low grade peanuts are also widely sold as a garden bird feed.

Peanuts have a variety of industrial end uses. Paint, varnish, lubricating oil, leather dressings, furniture polish, insecticides, and nitroglycerin are made from peanut oil. Soap is made from saponified oil, and many cosmetics contain peanut oil and its derivatives. The protein portion of the oil is used in the manufacture of some textile fibers. Peanut shells are used in the manufacture of plastic, wallboard, abrasives, fuel, cellulose and mucilage . Rudolf Diesel ran some of the first engines that bear his name on peanut oil and it is still seen as a potentially useful fuel.