Peanut, also known as groundnut is a crop of global importance. It is widely grown in the tropics and subtropics, being important to both smallholder and large commercial producers. It is classified as both a grain legume, and, because of its high oil content, an oil crop. World annual production is about 46 million tons per year. Very unusually among crop plants, peanut pods develop under the ground.
Peanuts are similar in taste and nutritional profile to tree nuts such as walnuts and almonds, and are often served in similar ways in Western cuisines. The botanical definition of a “nut” is a fruit whose ovary wall becomes very hard at maturity. Using this criterion, the peanut is not a nut, but rather a legume. However, for culinary purposes and in common English language usage, peanuts are usually referred to as nuts.
Peanut plants continue to produce flowers when pods are developing, therefore even when they are ready for harvest, some pods are immature. The timing of harvest is an important decision to maximize yield. If it is too early, too many pods will be unripe. If too late, the pods will snap off at the stalk, and will remain in the soil. For harvesting, the entire plant, including most of the roots, is removed from the soil. The fruits have wrinkled shells that are constricted between pairs of the one to four (usually two) seeds per pod.
