Vegetable · Fabaceae
Peanut
Arachis hypogaea
Give it full sun, loose sandy soil, and a long warm season, and the peanut sets a full crop underground.
Full sun
Every 5–10 days
64–95°F · 18–35°C
120–150 days
Overview
Among cultivated crops the peanut is a true curiosity. Its flowers open above ground in the ordinary way, but once a bloom is fertilized a specialized stalk, the peg, elongates downward and drives the young pod into the soil, so the kernels mature below the surface. Taxonomy places it with beans and peas in the legume family, not with the trees its common name evokes.
Originating in South America, the crop is governed by heat, which is why it succeeds in zones 7 through 11 and across the warm South where a long, frost-free season is assured. The plant remains compact, 8 to 20 inches tall, and expresses either an upright bunch or a prostrate runner habit according to the market type. What every type requires is sustained warmth, direct sun, and a full season to finish.
Soil physics and chemistry decide the yield. The peanut demands loose, sandy, calcium-rich ground because the peg must penetrate it and the pod draws calcium from that zone as it fills, and as a legume it fixes much of its own nitrogen through root nodules. Meet those conditions, hold moisture even through flowering, and the crop lifts heavy at the fall harvest.
Care
The short version: full sun, loose sandy soil rich in calcium, and about an inch of water a week while the plant flowers and sets pods. Keep nitrogen low, since the legume fixes its own, and taper the water as the pods mature.
Light
The peanut is a full sun crop that performs best with 8 or more hours of direct light daily. It tolerates a little partial sun, but reduced light produces weak, leggy growth and a sparse set of pods, since photosynthesis drives pod fill.
Water
Supply about 1 inch of water a week and hold the soil evenly moist through flowering and pegging, the window when the developing pods depend on steady moisture. As the pods mature, reduce the water so the crop can cure in the ground and lift cleanly at harvest.
Soil
Grow in loose, sandy, well-drained loam high in calcium, because the peg must penetrate the soil and the pod pulls calcium from that zone to fill. A slightly acidic pH of 5.8 to 6.5 suits the crop, and incorporating gypsum at bloom keeps calcium available where the pods form.
Temperature
As a heat-adapted crop the peanut works best between 64°F and 95°F (18°C to 35°C). It has no frost tolerance at either end of the season, so the extended warm middle is what accumulates the heat units the pods need to fill.
Humidity
Average humidity of 40% to 70% meets the plant's needs. Air movement matters more than the reading, because prolonged leaf wetness is precisely the condition that lets leaf spot establish.
Feeding
Because the peanut fixes its own nitrogen through root nodules, keep nitrogen low and prioritize phosphorus, potassium, and calcium instead. Incorporate gypsum at early bloom and pegging, the stage when pods begin forming and calcium demand in the pegging zone peaks.
Pruning
The peanut requires no pruning. Cultivate shallowly to suppress weeds during establishment, but stop once the pegs begin entering the soil, because any disturbance then damages the pods forming beneath the plant.
Repotting
not applicable; grown as a field/garden annual from seed each year
Size & spacing
Mature plants stand 8 to 20 inches (20 to 50 cm) tall and spread 12 to 35 inches (30 to 90 cm) as the runners extend. Spacing to that width gives every plant open soil for its pegs to reach and pod.
When to plant
The peanut is limited by season length, requiring an uninterrupted stretch of frost-free warmth to ripen its pods underground. Wait until the last frost has cleared and the soil has reached about 65°F, usually late spring, then allow a full growing season before lifting the crop in fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: After last frost when soil reaches about 65°F, typically late spring (May)
- Harvest: Yellow flowers appear ~6-8 weeks after planting; harvest pods in fall before frost when inner shells show veining and darkened color
Hardiness
USDA hardiness zones: 7–11
Temperature: down to -18°C
Troubleshooting
Peanut problems tend to develop out of sight, either in the buried pods or working upward from the oldest leaves. Understanding what a healthy stand should be doing at each stage is what lets you diagnose a fault before harvest. Match the symptom below to its cause, then intervene while the season still allows it.
Discolored, musty kernels in cure or storage
Discolored kernels, visible fuzzy mold, or a musty odor signal Aspergillus and the aflatoxin it secretes, a contamination that establishes when field drought stresses the crop or when pods dry and store damp. Because aflatoxin is a genuine health risk, discard any suspect nut and neither eat nor feed it. Curing pods promptly and holding them cool and dry denies the mold the moisture it needs.
Fix:
- Discard moldy peanuts; do not eat or feed them
- Dry pods promptly and thoroughly after harvest
- Store cured peanuts cool and dry
Vigorous foliage over empty or unfilled pods
A canopy that thrives while the pods stay blank points to calcium shortage or soil too compacted for the pegs, since the developing pod draws its calcium directly from the pegging zone rather than through the roots. Loosen that zone and supply gypsum at early bloom so each peg penetrates and each shell fills, and hold moisture even through pod set. Hilling heavy soil over the crown defeats the peg before it enters the ground.
Fix:
- Apply gypsum (calcium sulfate) at early bloom/pegging
- Grow in loose sandy soil and avoid hilling heavy soil over the crown
- Maintain even moisture during pegging and pod fill
Progressive dark lesions advancing up the canopy
Circular brown to black lesions, the early form often ringed by a yellow halo, identify early or late leaf spot, a Cercospora fungus that colonizes the oldest leaves first and advances upward whenever warmth and humidity linger. Because defoliation strips the photosynthetic surface, the yield falls with it. Interrupt the cycle by rotating off prior peanut residue, watering early so foliage dries fast, and applying a labeled fungicide on a preventive schedule.
Fix:
- Apply a labeled fungicide on a preventive schedule
- Remove or rotate away from previous peanut residue
- Improve air movement and avoid prolonged leaf wetness
Toxicity
The peanut carries no toxin in its foliage or in the plain kernels, so it is a safe, wholesome food for people and pets alike. The cautions attach to preparation rather than the plant: keep the nuts plain and unsalted, never feed moldy ones, and avoid peanut butter formulated with xylitol, which is dangerous to dogs.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
No compound in the plain peanut is toxic to cats. The practical hazards are mechanical and dietary: shells present a choking risk, and salted or fatty nuts can provoke stomach upset, so any treat should stay plain and minimal.
Dogs None
A few plain, unsalted peanuts suit most dogs. The material danger lies not in the nut but in certain peanut butters, where xylitol can drive vomiting, weakness, and collapse, so the label warrants a check before feeding.
Horses Safe
Neither the plant nor the plain nuts poison horses. Peanut hay in fact serves as forage in some regions, though the kernels are calorie dense and best offered only in small amounts.
Rabbits Safe
The peanut plant contains nothing toxic to rabbits, yet the nuts are too fatty and starchy for a hindgut fermenter. A diet of hay and greens serves them far better, so omit peanuts.
Livestock Safe
Cattle, goats, and sheep graze peanut foliage and hay without harm. The one real exposure is aflatoxin in spoiled feed, so moldy nuts and vines are the concern rather than the plant itself.
Birds Safe
Plain, unsalted peanuts are a standard feeder food for wild and pet birds. Keeping them dry matters, because ambient moisture cultures the molds that produce aflatoxin.
People Safe
Peanuts are a wholesome, protein-rich food consumed worldwide. The two cautions are a peanut allergy, which can be severe in sensitized individuals, and discarding any nut that smells musty or shows mold.
Salted or heavily seasoned peanuts add excess sodium and fat that are not ideal for pets and can cause stomach upset or pancreatitis with rich/fatty intake. MOLDY peanuts can carry aflatoxin and should never be fed. Critically, some commercial PEANUT BUTTER contains XYLITOL, an additive that is highly toxic to dogs even in small amounts and can cause hypoglycemia and liver failure; always check labels.
Varieties
The peanut divides into four principal market types, and the type determines kernel size, flavor, and end use. These are the names a grower should recognize.
Runner
A low, spreading type bearing medium kernels that accounts for most U.S. acreage and supplies most peanut butter.
Virginia
The large-kerneled type marketed as gourmet in-shell and cocktail peanuts.
Spanish
A small, round, red-skinned peanut with higher oil content, which is why it goes into candy and pressed oil.
Valencia
A sweet type that sets three or more kernels per pod and performs best boiled or roasted in the shell.
Companions
Plant near
Corn: Tall companion that does not compete heavily and benefits from the nitrogen peanuts fix.
Squash: Sprawling vines provide ground cover while peanuts enrich soil nitrogen.
Keep apart
Cabbage and other brassicas: Heavy feeders that compete and prefer firmer, less sandy soil management than peanuts.
How to propagate
The peanut reproduces from its own kernels, so a single packet of raw, viable seed peanuts is enough to establish a patch.
SeedModerate
Plant raw, viable seed (kernels) outdoors after last frost when soil is about 65°F · Germinates in about 7-14 days; full maturity in 120-150 days
Peanuts propagate from their own raw kernels, so viable seed must be fresh and untreated rather than roasted, which kills the embryo. Sow the kernels 1 to 2 inches deep in loose sandy soil after the last frost passes and the ground warms, and coat them with a Rhizobium inoculant so nodulation can fix more of the plant's nitrogen. Emergence follows in 7 to 14 days, but the geocarpic crop demands a full 120 to 150 days to mature underground.
Myths
Peanuts are tree nuts.
Botanically the peanut is no nut at all. It is a legume in the family Fabaceae, allied with beans and peas, and its pods mature underground after the flower stalk curves down into the soil. Sensitivity therefore does not cross over: a peanut allergy carries no automatic tree nut allergy, nor the reverse.
Peanuts grow on bushes or trees like other nuts.
The peanut exhibits geocarpy, a habit almost unique among crops. Once the flower self-pollinates, a specialized stalk called the peg elongates downward and drives the young pod into the soil, where the kernels enlarge and ripen below the surface.