Arachis hypogaea Seeds | White Peanut

Yellow pea flowers and four-leafleted foliage of a white peanut plant in sandy soil — White Peanut (*Arachis hypogaea*): Fabaceae, a South American domesticate now grown across the tropics and warm temperate zone.

LATIN NAME: Arachis hypogaea

COMMON NAME: White Peanut

Plant Profile

The peanut is not a nut, and it is barely a garden plant in the ordinary sense: it is an annual legume that flowers above ground and then buries its own pods. Plants grow twenty to fifty centimetres high and spread twice that, with four leaflets and a open, sprawling habit. Yellow pea flowers appear in the leaf axils about six weeks after sowing, and after pollination each flower’s stalk elongates into a peg that turns downward, pushes into the soil and develops the pod underground. That is geocarpy, and it is the reason peanuts are grown on loose, sandy ground: a hard or stony surface stops the pegs and the crop fails. White peanut is the name used in the seed trade for the pale-seeded Virginia and runner types, with two large seeds per pod and a papery red or pink skin. It is a tropical American plant, domesticated in the Andes and spread worldwide by the Portuguese.

Science & Biotechnology

Arachis hypogaea is an allotetraploid, 2n = 40, with an A and a B genome derived from two wild diploid ancestors, and it is almost entirely self-pollinating: the flowers self-fertilise before they open, so a field is a set of near-identical lines and breeding requires controlled crossing. The peg is a modified floral axis that responds to gravity and to touch, growing down until it enters the soil, where the ovary develops in darkness. Pods are therefore a soil-borne crop, which exposes them to Aspergillus flavus and to aflatoxin contamination, the single biggest quality problem in the crop worldwide and the reason storage moisture must stay below about ten percent. The plant nodulates with Bradyrhizobium but fixes less nitrogen than its biomass suggests, so it usually needs some starter nitrogen. Seed is rich in oil, about fifty percent, and in protein, and the skins carry resveratrol-family polyphenols.

Uses & Benefits

Peanuts are food first: roasted, boiled, pressed for oil, ground into paste and used as a protein source across Asia and Africa. The haulm, the leafy tops, is decent hay if cured properly. In China the seed is eaten fresh-boiled as a street food and the oil is a major cooking medium; peanut-skin tea is a folk tonic, and the skins are also a commercial source of polyphenols. In the garden the plant is worth growing as a curiosity and a small crop, particularly by people who want to show children how a pod forms underground. It is a poor competitor and needs warm soil, so it is a crop for the long-summer south rather than the cool temperate garden. The main risk in a wet season is mould on the pods, with the aflatoxin question that follows.

Growing from Seed

Sow shelled seed, with the skins left on, two to three centimetres deep in loose, sandy, warm soil once the ground is above 18 degrees; cold soil rots the seed. Space plants twenty centimetres apart in rows sixty apart, and keep the ground weed-free until the canopy closes. Water steadily until flowering, then keep the surface moist but not wet, because the pegs need to enter soil that is soft but not saturated. Do not cultivate around the plants after flowering, since the pegs are shallow and easily broken. Lift the whole plant when the leaves yellow and the pod shells show their veins, usually a hundred to a hundred and thirty days from sowing, and cure it in a dry, airy place for two weeks before shelling. In cool climates, grow it under cover or treat it as a novelty.

Our Take

A warm-season crop for loose sandy ground, grown as much for the curiosity of buried pods as for the harvest. Do not sow until the soil is properly warm.

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