Vegetable · Solanaceae
Potato
Solanum tuberosum
Plant a few cut tubers, hill the soil, keep it watered, and dig a heavy crop come fall.
Full sun
Every 3–7 days
50–77°F · 10–25°C
70–120 days
Overview
The potato is a cool-season tuber crop and a member of the nightshade family, the same clan as the tomato and pepper. It came out of the Andes, where it was bred for food thousands of years before it crossed to the rest of the world. What you eat is the tuber, a swollen underground stem the plant fills with starch, and not a root at all.
Growing potatoes is mostly about what happens below the soil. You plant cut pieces of seed potato, each carrying an eye, and the plant sends up leafy stems while it builds tubers on short shoots underground. The single most important job is hilling, mounding soil up the stems so the new tubers stay buried and dark. A tuber that catches the light turns green and bitter.
Give them loose, fertile ground on the acidic side and even water once the tubers set, and a small patch can keep a kitchen going for months. They store well too, so a fall harvest carries you well into winter.
Care
The short version: full sun, loose and slightly acidic soil rich in organic matter, and even moisture once the tubers begin to form. Feed at planting, go easy on the nitrogen, and hill soil up the stems as the plants grow.
Light
Potatoes want full sun, ideally 6 or more hours of direct light a day. They will scrape by in partial sun, but the tops grow weaker and the tubers come in smaller, so give them the most open spot you have.
Water
Keep the soil evenly moist, which works out to about 1 to 2 inches of water a week, and stay especially steady once the tubers begin to swell. Don't let it sit waterlogged, though, since soggy ground brings on rot and disease.
Soil
Plant in loose, well-drained sandy loam with plenty of organic matter worked in. Potatoes like it on the acidic side, a pH of 5.0 to 6.0, which also keeps scab in check, and the loose texture lets the tubers swell freely.
Temperature
They grow best in cool weather, somewhere between 50°F and 77°F (10°C to 25°C). Tuber growth slows once the heat climbs, so an early start beats the worst of summer.
Humidity
Average outdoor humidity suits them fine, so there's no number to hit. Airflow is what counts, since damp, crowded foliage is exactly what late blight needs to take hold.
Feeding
Work a balanced fertilizer into the bed at planting, then side-dress with a little nitrogen as the plants come up and you hill them. Go easy, though, because too much nitrogen grows lush tops at the expense of the tubers you actually want.
Pruning
There's no real pruning to do. Just pull off diseased foliage as soon as you spot it, and keep hilling soil up the stems to bury the developing tubers and stop them greening in the light.
Size & spacing
Plants reach 1 to 3 feet (30 to 100 cm) tall and spread 12 to 24 inches (30 to 60 cm) across. Give each one room and mound the soil generously, since that buried space is where the crop forms.
When to plant
Potatoes go in early while the ground is still cool. Plant the seed pieces 2 to 4 weeks before your last frost, once the soil sits around 45°F to 50°F (7°C to 10°C), then dig new potatoes from midsummer and lift the main storage crop in fall after the tops die back.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Early spring, about 2-4 weeks before the last expected frost once soil reaches roughly 45-50°F
- Harvest: Harvest new potatoes about 60-70 days after planting; harvest mature storage potatoes about 90-120 days after planting once tops die back
Hardiness
USDA hardiness zones: 3–9
Temperature: down to -40°C
Troubleshooting
Most potato problems either show up on the leaves while the plants are growing or on the tubers when you dig them. Learn the few that matter and you can act before they spread. Match what you see below, then deal with it while it still counts.
Greasy dark blotches and foliage that collapses in wet weather
This is late blight, the same Phytophthora that ruins tomatoes, and it races through a planting after a cool, damp spell. Watch for spreading brown-black lesions with pale edges and white fuzz on the leaf undersides on humid mornings. Pull and destroy infected plants at once, never compost them, and cull any rotted tubers before they reach storage.
Fix:
- Remove and destroy infected plants immediately
- Do not compost infected material
- Apply an approved fungicide preventively where blight is present
- Harvest carefully and cull infected tubers before storage
Striped beetles and red grubs stripping the leaves
The Colorado potato beetle is the worst pest of the crop, and a heavy run can strip a plant bare. Check leaf undersides for orange egg clusters, soft red larvae, and the adults with their ten black stripes. Handpick everything into soapy water, cover young plants with row cover, and move the planting to fresh ground each year.
Fix:
- Handpick adults, larvae, and egg masses into soapy water
- Use row covers early in the season
- Apply an approved insecticide if infestation is heavy
- Rotate planting location yearly
Green skin on tubers, sometimes turning bitter
A tuber turns green when light reaches it near the soil surface, and that green tissue carries solanine, the toxin that makes a potato bitter and unsafe. Usually it traces back to thin hilling that left the tubers exposed. Mound soil over them as the plants grow, throw out any heavily greened potatoes, and store the harvest somewhere cool and dark.
Fix:
- Hill soil up over exposed tubers as plants grow
- Discard heavily greened tubers
- Store harvested potatoes in cool, dark conditions
- Cut away minor green areas before cooking
Rough, corky scabs on the tuber skins
These corky patches are common scab, a soil bacterium that flares when the ground runs dry during tuber set or the pH climbs too high. Peel one tuber to check: the lesions stay shallow and the flesh underneath is sound, so the crop is still good to eat. Keep the soil evenly moist while tubers form, hold the pH down around 5.0 to 5.5, and skip the fresh manure.
Fix:
- Maintain even soil moisture during tuber formation
- Keep soil pH slightly acidic (around 5.0-5.5)
- Plant scab-resistant cultivars
- Avoid fresh manure and alkaline amendments
Toxicity
The cooked tuber is a safe, everyday food, but the rest of the plant is not. The foliage, stems, sprouts, and any green or raw potato carry a natural toxin called solanine that can sicken people and animals alike. Cut away green spots, throw out badly greened tubers, and keep the vines and sprouts away from pets, livestock, and children.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Caution
A cat that chews the leaves, stems, or a green sprouted tuber takes in solanine and tends to drool and vomit, with diarrhea and low energy to follow. A big dose can reach the heart and nervous system, so call a vet if more than a nibble went down.
Dogs Caution
Dogs that dig up and gnaw raw or green tubers, or browse the foliage, usually show an upset stomach, loose stools, and a sluggish mood. Watch them closely, since heavier amounts of glycoalkaloid can affect the heart rhythm.
Horses Caution
The vines and any green or sprouted potatoes are off limits for horses. Solanine brings on colic, drooling, and a dull, wobbly stance, and a horse grazing fallen foliage can take in enough to need a vet.
Rabbits Caution
Never let a rabbit at the leaves, stems, or green tubers, because their small size means even a little solanine causes real trouble. Expect a poor appetite, a bloated belly, and weakness if any is eaten.
Livestock Caution
Cattle, sheep, pigs, and goats can poison themselves on discarded vines or piles of green and cull potatoes left in the field. The solanine triggers digestive upset along with staggering and trembling once enough builds up.
Birds Caution
Keep chickens and other birds away from the foliage, sprouts, and any greened scraps, all of which hold solanine. Cooked plain potato in small amounts is fine, but the green raw parts are not.
People Cooked tuber safe
A cooked, properly stored potato is a safe everyday staple. The danger sits in the green skin, the sprouts and eyes, and all the foliage and stems, which carry solanine that turns a potato bitter and can sicken you, so cut away green spots, toss any badly greened tuber, and keep the vines off the plate.
Cooked, properly stored potato tubers are a safe food. The hazard is the foliage and any green, raw, or sprouted tubers, which contain solanine.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Hundreds of potato varieties exist, sorted mostly by skin color, flesh texture, and what they cook up best for. These four turn up in most gardens and shops.
Yukon Gold
A thin-skinned yellow potato with buttery, all-purpose flesh that has become the standard kitchen variety.
Russet Burbank
A large, oblong, brown-skinned potato so starchy that it is the go-to choice for baking and frying.
Red Pontiac
A red-skinned, white-fleshed variety prized for steady yields and how well it keeps in storage.
Kennebec
A vigorous white potato that crops heavily and shrugs off more disease than most.
Companions
Potatoes do well beside nitrogen-fixing beans and a few traditional partners, and badly beside their nightshade relatives and sprawling vines that crowd them and trade diseases.
Plant near
Bush beans: Legumes fix nitrogen and are reported to help repel some potato pests.
Corn: Traditional companion that does not compete heavily and shares no major potato diseases.
Cabbage-family crops: Generally compatible bed companions that do not share potato's key diseases.
Horseradish: Often planted near potatoes and is said to improve overall plant vigor and pest resistance.
Keep apart
Tomato: Another solanaceous crop that shares late blight and other diseases, increasing risk to both.
Cucumbers and squash: Sprawling cucurbits crowd potatoes and can increase disease pressure.
How to propagate
There are two ways to start potatoes, but for nearly every gardener only one of them makes sense.
Bulbs & cormsEasy
Early spring, 2-4 weeks before the last frost · Sprouts emerge in about 2-4 weeks after planting
Almost everyone grows potatoes from certified seed-potato pieces, each cut to carry one or two eyes and left to cure for a day or two before going in the ground. Plant them in early spring, 2 to 4 weeks before the last frost, about 4 inches deep, and the sprouts break through in roughly 2 to 4 weeks. Keep hilling soil up the stems as the plants climb.
SeedDemanding
Indoors in late winter · Several weeks to germinate and grow on before transplanting
Starting from true botanical seed is a different job altogether, sown indoors in late winter and grown on for several weeks before it can be transplanted. The offspring come out variable, so home growers rarely bother and the method stays mostly with breeders.
Myths
Every part of the potato plant is safe to eat because the tubers are a common food.
Only cooked tubers that have been stored properly and never turned green are safe. The foliage, stems, sprouts, and any green or raw tuber carry solanine, which is genuinely toxic, so the plant on the whole is not a free-for-all.
Potatoes have to be grown from true seed like other vegetables.
Almost every home grower plants certified seed-potato pieces, each cut to carry one or more eyes. True botanical seed is rarely used outside of breeding, since it produces a mixed bag of unpredictable offspring.