While “nut” is in their name, peanuts are in fact legumes. Peanuts actually grow underground, as opposed to nuts like walnuts, almonds, etc. that grow on trees (and are sometimes referred to as "tree nuts").
Peanuts, along with beans and peas, belong to the single plant family, Leguminosae. Legumes are edible seeds enclosed in pods. As a group, they provide the best source of concentrated protein in the plant kingdom. While their physical structure and nutritional benefits more closely resemble that of other legumes, their use in diets and cuisines more closely resembles that of nuts.
Peanut seeds (kernels) grow into a green oval-leafed plant about 18 inches tall, which develop delicate yellow flowers around the lower portion of the plant. The flowers pollinate themselves and then lose their petals as the fertilized ovary begins to enlarge. The budding ovary or 'peg' grows down away from the plant, extending to the soil. The peanut embryo turns horizontal to the soil surface and begins to mature, taking the form of the peanut. From planting to harvesting, the growing cycle takes four to five months, depending on the type or variety.
In the U.S., peanuts and peanut butter are the most popular nut choice and comprise 67% of all nut consumption.
© USDA-ERS, 2009