Vegetable · Fabaceae
Peanut
Arachis hypogaea
Give it full sun, loose sandy soil, and a long warm season, and the peanut swells a whole crop of shells underground.
Full sun
Every 5–10 days
64–95°F · 18–35°C
120–150 days
Overview
Up close the peanut is a low, leafy plant that hides its strangest feature underground. Small yellow flowers open along the stems, and once a bloom is pollinated a slender stalk called the peg curves downward and pushes the young pod into the soil, so the kernels fatten out of sight. For all the nutty look of the finished kernel, the plant sits in the bean and pea family rather than among the nut trees.
The plant keeps close to the ground, 8 to 20 inches tall, its green foliage either mounding into a compact bunch or trailing out in low runners depending on the type. Native to South America, it holds this leafy, spreading shape through a long, warm season across zones 7 through 11 and the South. The stems stay soft and green, never woody.
Underground the peanut does its real work in loose, sandy ground rich in calcium, where the pegs drive down and the shells swell and fill. At harvest the pods pull up rough and tan, and the inner shells show the veining and darkened color that mark a ripe crop. As a legume it fixes much of its own nitrogen through the roots below.
Care
The short version: the peanut takes full sun, loose sandy soil rich in calcium, and about an inch of water a week while its yellow flowers open and the pods set. Nitrogen stays low, since the plant makes its own, and the water eases off as the shells fill and mature.
Light
The peanut wants full sun, ideally 8 or more hours a day, which keeps the leaflets broad and deep green. In too much shade the stems stretch weak and leggy and the plant sets only a thin crop of pods.
Water
The plant takes about 1 inch of water a week, and the soil stays evenly moist while the yellow flowers open and the pegs drive into the ground. That stretch swells the kernels inside their shells. As the pods mature, the water eases off so the shells cure firm and the crop lifts cleanly.
Soil
The peanut roots into loose, sandy, well-drained loam high in calcium, the open texture the slender pegs need to push through and the shells need to fill. A slightly acidic pH of 5.8 to 6.5 suits it, and gritty gypsum worked in at bloom keeps the calcium right where the pods form.
Temperature
The peanut is a heat lover, greenest and most productive between 64°F and 95°F (18°C to 35°C). Frost blackens it at either end of the season, so it is the long warm middle that swells and fills the shells.
Humidity
Average humidity between 40% and 70% suits the plant. Air moving through the leafy canopy matters more than the number, since long spells of wet foliage are what let the dark spots of leaf spot take hold.
Feeding
Because the peanut fixes its own nitrogen through its roots, nitrogen stays low and phosphorus, potassium, and calcium take the lead. Gypsum worked in at early bloom and pegging arrives just as the pods begin to form and the shells reach for calcium.
Pruning
The peanut needs no pruning at all, and the soft green stems are left whole. Shallow cultivation clears weeds early on, but once the pale pegs begin entering the soil the ground stays undisturbed so the swelling pods are not torn.
Repotting
not applicable; grown as a field/garden annual from seed each year
Size & spacing
The plant stays low, 8 to 20 inches (20 to 50 cm) tall, its foliage spreading to 12 to 35 inches (30 to 90 cm) as the runners creep out. That much room gives each plant open soil for its pegs to reach and pod.
When to plant
The peanut needs a long, frost-free run of warmth for its shells to swell and ripen underground. The last frost passes and the soil warms to about 65°F, usually late spring, before the kernels go in, and a full season of leafy growth follows before the pods are dug 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
Most of what goes wrong with a peanut shows on the plant if you look closely, either in the buried shells or across the green leaflets of the lower stems. Reading the color, texture, and spread of the symptom points straight to the cause. Match what you see below before harvest arrives.
Discolored, fuzzy kernels in the shell
Kernels that have darkened or dulled from their normal color, a fuzzy gray-green film on the skin, and a musty smell in the shell all reveal Aspergillus and the aflatoxin it produces, set off by drought stress in the field or damp storage. Any kernel that looks or smells off is thrown out, never eaten and never fed. Curing the pods quickly and keeping them cool and dry stops the mold from ever taking hold.
Fix:
- Discard moldy peanuts; do not eat or feed them
- Dry pods promptly and thoroughly after harvest
- Store cured peanuts cool and dry
Green leafy tops over thin, hollow pods
When the vines stay lush and green but the shells feel light and hollow in the hand, the trouble is calcium starved or compacted soil in the pegging zone. The slender pegs need loose ground to slip into and calcium to plump the kernels inside their shells, so gypsum worked in at early bloom and even moisture through pod fill set it right. Heavy soil packed over the crown stops the pale pegs cold before they reach the dirt.
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
Dark spots freckling the lower leaflets
Small round spots in brown to black, many rimmed by a soft yellow halo, freckle the oldest leaflets first and mark early or late leaf spot, a fungus that climbs the plant through warm, humid weather. As the spots multiply the green leaflets yellow, curl, and drop, leaving the stems bare and the crop lighter. Morning watering that dries the leaves, rotation off old peanut ground, and a labeled fungicide keep the foliage clean.
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 green plant and its plain kernels carry no toxin, so the peanut is a safe, wholesome food for people and pets alike. The cautions are about what happens to the kernels after harvest: keep them plain and unsalted, never feed moldy ones, and avoid peanut butter that contains xylitol, which is dangerous to dogs.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A plain kernel carries nothing that poisons a cat. The dry, papery shell is a choking hazard, though, and salty or oily nuts can upset the stomach, so any treat stays plain and small.
Dogs None
A few plain, unsalted kernels sit fine with most dogs. The real hazard is not the nut but xylitol in some peanut butters, which can bring on vomiting, weakness, and collapse, so the label deserves a look first.
Horses Safe
The leafy plant and the plain kernels hold no poison for horses. The dried vines even serve as peanut hay forage in some regions, though the oily kernels are best fed in small amounts.
Rabbits Safe
Nothing in the peanut plant is toxic to rabbits, but the dense kernels are too fatty and starchy for them. Leafy hay and greens suit them far better, so the nuts are best left aside.
Livestock Safe
Cattle, goats, and sheep graze the green foliage and dried hay without harm. The one worry is moldy nuts and vines, since aflatoxin can gather in feed that has spoiled.
Birds Safe
Plain, unsalted kernels are a favorite feeder food for wild and pet birds alike. Keeping them dry matters, since damp nuts grow the fuzzy molds that make aflatoxin.
People Safe
The kernels are a wholesome, protein-rich food eaten worldwide. The lasting caution is a peanut allergy, which can be serious in sensitive people, along with discarding any kernels that smell musty or look moldy.
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 comes in four main market types, and each carries kernels of a different size, shape, and skin color. These are the names worth knowing before the crop goes in.
Runner
A low, spreading type whose medium, evenly sized kernels fill most U.S. acreage and go into most peanut butter.
Virginia
The type with the largest kernels, sold as gourmet in-shell and cocktail peanuts.
Spanish
A small, round peanut wrapped in a reddish skin and richer in oil, which is why it goes into candy and pressed oil.
Valencia
A sweet type whose long pods hold three or more kernels apiece and eat 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 grows from its own kernels, so a single packet of raw seed peanuts is all it takes to start a leafy 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
The peanut grows from its own raw kernels, so the seed is a fresh, untreated nut rather than a roasted one. Each kernel goes 1 to 2 inches deep into loose sandy soil once the frost has cleared and the ground has warmed, and a dusting of powdery Rhizobium inoculant on the skin helps the plant fix more of its own nitrogen. Green seedlings push up in 7 to 14 days, while the pods below take a long 120 to 150 days to swell and ripen underground.
Myths
Peanuts are tree nuts.
For all that a peanut looks like a nut in the bowl, it is none. It is a legume in the family Fabaceae, a relative of beans and peas, and its pods swell and ripen underground after the flower stalk bends down into the soil. A peanut allergy does not automatically carry a tree nut allergy, and the reverse holds just as true.
Peanuts grow on bushes or trees like other nuts.
The peanut does something you can watch above the soil. After a small yellow flower pollinates itself, a slender stalk called the peg curves down from the plant and drives the young pod into the ground, where the kernels fatten and ripen out of sight.