The Incredible Peanut :: Botany

The Incredible Peanut According to Webster's New Collegiate Dictionary, a peanut is "a low-branching, widely cultivated, leguminous, annual herb with showy yellow flowers having a peduncle which elongates and bends into the soil where the ovary ripens into a pod containing one to three edible seeds" (7). However, this definition does not even begin to give any indication of the importance of the peanut as an agricultural power in the world today. Therefore, this paper will discuss the peanut including its history, economic uses, and other pertinent information regarding this amazing plant. The scientific name for the common, commercially grown peanut is Arachis hypogaea L. Contrary to popular opinion, however, the peanut is not really a nut such as a pecan or walnut. It is actually a close relative of the black eyed pea in the family Leguminosae. Legumes are plants in which the roots contain nodules of nitrogen fixing bacteria which return remarkable amounts of nitrogen to the soil. Logically, the peanut is a perfect crop to rotate in with soil depleting plants like cotton and is used extensively for this purpose (8). The peanut plant is a sparsely hairy, taprooted, annual bush about 45 cm tall when mature. The four main botanical varieties are Virginia, Spanish, Valencia, and Peruvian Runner. They are distinguished from each other by branching habit, branch length, and hairiness. The most interesting facet of peanut growth is the development of the seeds. After the small, yellow flowers pollinate themselves, the stalks at the bases of the ovaries, called pegs, elongate rapidly and turn downward due to geotropism. The peg then buries itself several inches in the ground to mature in approximately four months (6). In order for peanuts to be grown efficiently, several habitat criteria must be met. One of these is a suitable climate. For best yields, peanuts require a growing period of 4-5 months with a steady, rather high temperature and an annual rainfall of about 50-100 cm. The growing season must be long, warm and moist, but the harvest season must be dry so the pods will pull out of the ground. Another requirement is a light-col6red, well drained, sandy loam soil. If the peanuts are grown in too heavy soil, the pods will remain in the ground when the plants are harvested (4). Peanuts are grown in countries with warm climates all around the world. India produces about six million metric tons annually and is easily the world's leading producer.