Peanuts (Arachis hypogaea) are an important field crop in the southeastern United States. In 1995, peanuts were grown on 1.5 million acres in the United States. and produced a crop of 3.5 billion pounds. Peanut seeds (kernels) are used for peanut butter, oil, flour, roasted peanuts, and other food products. While they are not widely grown in Iowa, their unique growth habit makes them a fun addition to the home garden.
Peanuts are also known as goobers, goober peas, groundpeas, ground nuts, and earth nuts. The peanut is a legume with compound leaves similar to clover and yellow, pea-like flowers. Peanut varieties can be classified by growth habit (bunch or runner) and nut type (Virginia or Spanish). Virginia types are large podded and usually contain 1 or 2 large kernels per pod. Spanish types are smaller podded and contain 2 or 3 small kernels per pod.
Peanuts grow best in loose, well-drained soils. Avoid poorly drained, clay type soils. Plant peanuts after the danger of frost is past. Peanuts require a soil temperature of 65 F for germination. Sow peanut seeds 1 to 1 1/2 inches deep and 6 to 8 inches apart. Row spacing for bunch types should be 24 inches and 36 inches for runner types. Suggested varieties for home gardens include 'Spanish,' 'Early Spanish,' 'Virginia Improved,' and 'Jumbo Virginia.' Peanuts are warm-season annuals that require a minimum of 120 frost free days to reach maturity.
The flowering and fruiting of peanuts are unique. Plants flower above ground, but the pods develop below ground. Peanut plants begin to bloom about 30 to 40 days after emergence. The flowers are small, bright yellow, and pea-like in appearance. After pollination and fertilization occurs, the stalk (peg) below the fertilized ovary elongates and curves downward. It takes about 10 days for the peg to penetrate into the soil. A week after soil penetration, the peg tip enlarges and pod and seed development begin. The fruit mature in 9 to 10 weeks with favorable temperatures and moisture conditions. Since the peanut plant flowers over several weeks, all the pods do not mature at the same time.
Cultivate the soil around peanut plants to control weeds and to keep the soil loose so the pegs can easily penetrate the soil surface. Cultivate shallowly to prevent damage to the peanut roots. Stop cultivation in the immediate vicinity of the plants when the pegs begin to penetrate into the soil. A 1 or 2 inch layer of mulch can be placed around plants in early June to control weeds. Any weeds that do appear can be hand pulled.
Harvest the peanuts when the foliage begins to yellow in late summer or early fall. Dig up the plants with a spading fork and carefully shake off the loose soil. Cure the peanuts by hanging the plants in a warm, dry shed or garage. Beware of mice. After the plants have dried for 1 or 2 weeks, shake off any remaining soil and pull the peanut pods from the plants. Continue to air dry the peanuts for an additional 1 or 2 weeks. Once dried, place the peanuts in mesh bags and store them in cool, well-ventilated place until roasted.
This article originally appeared in the May 2, 1997 issue, p. 56.