Overview
What potatoes need, when they crop, and whether they suit your plot.
Potatoes grow from seed potatoes: small tubers that sprout and set a cluster of new ones underground. Earlies give new potatoes by midsummer, often before blight strikes; maincrops fill out until autumn and store through winter. Keep the tubers covered and evenly watered, because light turns them green and patchy watering makes them crack.
Quick facts
- Botanical name
- Solanum tuberosum
- Soil pH
- 5.8 – 6.5
- Feeding
- Heavy feeder
- Temperature
- 16 – 21 °C
- Hardiness
- Any zone, as an annual
- Time to harvest
- 84 – 120 days
- Height
- Up to 90 cm (35 in)
- Propagation
- Tuber
Optimal growth
Killed by frost
Growing details
- Spacing
- 30 cm (12 in)
- Sowing depth
- 120 mm (5 in)
- Frost sensitivity
- Frost tender
Growing calendar
- Start indoors: January, February, March
- Plant out: March, April, May
- Harvest: June, July, August, September, October
Chit early varieties for four to six weeks before planting (RHS). First earlies late March, second earlies early to mid-April, maincrops mid-April to early May (RHS). First earlies June and July, second earlies July and August, maincrops late August to October (RHS).
Is this plant right for you?
- Beginner friendly
- Big harvest
- Grows in bags
- Stores for months
- Needs space
- Frost-tender shoots
- Rotate each year
Toxic to people
Green tubers contain solanine, which can cause severe stomach upsets. Cut away green patches; discard very green potatoes. Never eat potatoes raw.
Before You Grow
Choose earlies or maincrops, buy certified seed potatoes, and prepare an open, sunny bed.
Earlies are usually lifted before blight takes hold (Gardeners’ World).
What you need
Certified seed potatoes
Firm, disease-free tubers. See choose your potatoes.
Egg boxes or trays
For chitting earlies. See chitting.
An open, sunny bed
Where potatoes and tomatoes didn’t grow last year. See soil.
Spade, hoe and fork
For trenches, earthing up and lifting. See earthing up.
Fleece
For frosty nights after shoots appear. See care by stage.
Or a big container
A pot, sack or grow bag. See containers.
Choose your potatoes
Varieties are grouped by how long they take to crop (RHS).
First earlies give new potatoes in as little as 12 weeks. The plants are compact, suit containers, and are dug by midsummer, freeing the ground for another crop. RHS AGM choices: ‘Red Duke of York’, ‘Casablanca’, ‘Maris Bard’.
Second earlies follow a few weeks later: salad types such as ‘Charlotte’ and ‘Nadine’.
Maincrops stay in the ground until late summer or early autumn and give bigger crops of larger potatoes for roasting, baking and storing: ‘Maris Piper’, ‘Desiree’, ‘Sarpo Mira’.
Texture. Waxy potatoes hold their shape (salads, boiling); floury ones fluff up (baking, mash).
In the US, Iowa State suggests ‘Red Norland’, ‘Yukon Gold’ and ‘Superior’ (early, scab resistant), and ‘Kennebec’ and ‘Katahdin’ (late).
Blight. Blight-resistant varieties such as ‘Blue Danube’ help in wet summers (Gardeners’ World).
Potato types compared
-
First early
- Plant (UK)
- Late March
- Lift (UK)
- June to July
- Spacing
- 30 cm (1 ft), rows 60 cm (2 ft)
- Best for
- New potatoes, containers
-
Second early
- Plant (UK)
- Early to mid-April
- Lift (UK)
- July to August
- Spacing
- 30 cm (1 ft), rows 60 cm (2 ft)
- Best for
- Salads, new potatoes
-
Maincrop
- Plant (UK)
- Mid-April to early May
- Lift (UK)
- Late August to October
- Spacing
- 37 cm (15 in), rows 75 cm (30 in)
- Best for
- Baking, roasting, storing
Timings and spacing from the RHS. For a small plot, grow earlies; for winter storage, grow a maincrop.
Where potatoes grow best
Potatoes are a cool-season crop (Illinois).
Sun. An open, sunny site with at least six hours of direct sun (Iowa State); UMD prefers eight to ten.
Frost. Plants withstand a light frost but not a hard one (UMD), and young shoots are easily damaged in April and May (RHS). Avoid frost pockets.
Soil temperature. Plant into soil of at least 7 °C (45 °F) (UMD); Utah State waits for 10 °C (50 °F). Tubers form best at 16 to 21 °C (60 to 70 °F) and fail to form at 27 °C (80 °F) (Illinois), so hot summers mean small crops.
Rotation. Grow potatoes in a new spot each year to avoid a build-up of pests and diseases (RHS).
- Plant into soil at
- At least 7 to 10 °C (45 to 50 °F)
- Tubers form best
- 16 to 21 °C (60 to 70 °F) soil
- Sun
- At least 6 hours
Soil
Potatoes like loose, fertile, well-drained, slightly acid soil (Iowa State). Tubers come out misshapen in hard, compacted ground (Illinois).
Organic matter. The RHS digs in plenty of compost or well-rotted manure, ideally the autumn before. Iowa State warns that heavy dressings of manure can increase scab, and Utah State keeps compost to about 2.5 cm (1 in).
pH. 5.8 to 6.5 (Clemson); 6.0 to 6.5 (UMD). Where scab is a problem, a pH of 5.0 to 5.3 reduces it (Clemson).
Fertiliser. A general fertiliser worked in shortly before planting, following a soil test if you have one (Iowa State, Utah State).
Planting
Chit earlies in late winter, then plant from early spring as the soil dries and warms.
Seed pieces rot in cold, wet soil: wait until it has dried and warmed a little (Illinois).
When to plant potatoes
Plant from early spring as soon as the soil can be worked and has dried and warmed a little. Seed pieces rot in cold, wet soil, and moderately early plantings often do as well as very early ones (Illinois).
In the UK, first earlies around late March, second earlies early to mid-April, maincrops mid-April to early May. Plant a little later in colder areas (RHS).
In the US, two to three weeks before the last frost (Utah State); early to mid-April in central Iowa (Iowa State).
Extra crops. Earlies planted in large pots in a frost-free greenhouse in early March crop by mid-May. Cold-stored seed potatoes planted in July or early August under cover give a winter crop (RHS).
- Soil workable and no longer cold and wet.
- Earlies first, maincrops a month later.
- Protect shoots from late frosts.
Chitting and preparing seed potatoes
Chitting (sprouting) earlies before planting brings the crop forward by a few weeks. It isn’t essential, and there’s little gain for maincrops (RHS).
-
Buy certified seed
Firm, disease-free seed potatoes, in late winter. Supermarket potatoes may carry disease or be treated against sprouting (Iowa State, Illinois).
-
Set them eyes up
In egg boxes or trays, with the end with the most eyes uppermost (Gardeners’ World).
-
Keep cool and bright
Frost-free, in good light, for four to six weeks, until the sprouts are about 5 cm (2 in) long. Start in late January in mild areas, up to early March in cold ones (RHS).
-
Thin the sprouts
A seed potato needs only one or two shoots; rub off extras if you like (Gardeners’ World).
-
Cut large tubers (optional)
US extensions cut big seed potatoes into pieces of about 40 to 55 g (1½ to 2 oz) (UMD, Illinois), each with at least one eye, and let the cut surfaces heal for a few days before planting (Iowa State, Clemson). Small potatoes go in whole.
How to plant potatoes
In a trench or individual holes, sprouts upwards.
-
Dig a trench
About 12 to 15 cm (5 to 6 in) deep (RHS, Gardeners’ World). US guides plant 7.5 to 15 cm (3 to 6 in) deep, deeper for later crops.
-
Space the seed potatoes
Earlies 30 cm (1 ft) apart in rows 60 cm (2 ft) apart; maincrops 37 cm (15 in) apart in rows 75 cm (30 in) apart (RHS).
-
Set them upright
Sprouts upwards, or cut side down (Iowa State).
-
Cover gently
Fill in the trench without knocking off the sprouts, then water well (RHS).
-
Or plant under mulch
Set seed potatoes on or just in the soil surface and cover with 10 to 15 cm (4 to 6 in) of straw (Illinois, Utah State; Clemson uses 30 to 45 cm, 12 to 18 in), topping up as it settles; tubers form in the straw and lift out cleanly (Illinois, Utah State). No-dig growers use deep compost the same way (RHS).
Care
Earth up, water evenly while tubers form, and keep frost off young shoots.
Tubers form best in soil at 16 to 21 °C (60 to 70 °F) and stop forming at 27 °C (80 °F) (Illinois).
Care by growth stage
Shoots emerging
Frost: protect shoots
Cover with fleece, straw or soil if frost is forecast (RHS). See growing conditions.
Young plants
Earth up: at 20 to 23 cm
Weed shallowly for the first month or two. See earthing up.
Flowering
Water: 2.5 cm (1 in) a week
Tubers are forming: water evenly. See watering.
Tubers swelling
Blight: check leaves
Keep them covered and watch for blight. See diseases.
End of season
Storage: skins set first
Water less as the foliage yellows, then lift. See harvesting.
Earthing up
Earthing up (hilling) means drawing soil up around the stems as they grow. It protects shoots from late frost, gives tubers loose soil to grow in, and keeps them in the dark so they don’t turn green (RHS, Iowa State).
When. Once shoots are about 20 to 23 cm (8 to 9 in) tall, draw soil up to leave the top 10 cm (4 in) showing. Repeat a few times, a few weeks apart, to a ridge 20 to 30 cm (8 to 12 in) high (RHS). Utah State starts within four weeks of planting.
How. With a hoe or spade, working from between the rows. Keep it shallow near the plants: tubers are easily cut (Illinois).
Skipping it. You’ll still get a crop (RHS), especially under a thick straw mulch.
- Start at 20 to 23 cm (8 to 9 in).
- Leave the top 10 cm (4 in) showing.
- Repeat to a ridge 20 to 30 cm (8 to 12 in) high.
Watering potatoes
Even moisture matters most while tubers form, from around flowering onwards (Iowa State, Clemson).
How much. About 2.5 cm (1 in) a week, deeply once a week in dry weather (Iowa State); Utah State allows up to 5 cm (2 in) in its hot, dry climate.
Even, not erratic. Alternating wet and dry spells cause hollow heart, cracks and knobbly tubers (Iowa State, Utah State).
How. At the soil, not over the leaves, which spreads disease (UMD, Gardeners’ World).
Mulch keeps the soil cooler and moist; straw can keep it about 5 °C (10 °F) cooler (Illinois).
Late season. Water less as leaves yellow: wet soil late on leads to rot in storage (Utah State).
Feeding potatoes
In well-prepared ground, potatoes rarely need more (RHS).
Before planting. A general fertiliser, following a soil test if you have one (Iowa State, Utah State).
Side dressing. On poor soil, maincrops benefit from a nitrogen-rich feed when earthing up (RHS). US extensions side-dress about six weeks after emergence, as tubers begin to form (Utah State, UMD).
Not too much. Heavy feeding makes leaves at the expense of tubers (Utah State).
Containers need feeding: fertiliser in the compost, then a liquid feed after about six weeks (RHS).
Potatoes in containers
Earlies suit containers best: the plants are smaller and crop sooner (RHS).
Container. At least 30 cm (12 in) wide and deep, with drainage holes: a pot, a grow bag or a sack. One seed potato per 30 cm (12 in) of width.
Plant just below the surface of 15 cm (6 in) of compost, then add more as shoots grow until it reaches just below the rim (RHS).
Water often: the leaves shed rain away from the pot. Keep pots under cover until the frosts are over.
Harvest by tipping the pot out. UMD notes that tall potato "towers" don’t usually work.
Problems
Blight, scab, slugs and green tubers are the troubles to watch for.
Common potato problems
Light, water and heat cause many tuber problems.
Green patches on tubers
- Light
Tubers exposed to light make bitter, toxic solanine. Earth up well and store in the dark; cut away small green patches and discard very green potatoes (Utah State, UMD).
Cracks, knobs and hollow hearts
- Uneven water
Alternating wet and dry soil while tubers grow (Iowa State). Water evenly and mulch.
Many small, odd-shaped tubers
- Heat
Soil too hot for tubers to set and fill (Utah State). Plant early and mulch heavily.
Seed potatoes rotted
- Cold, wet soil
Planted into cold, wet soil (Illinois). Wait until it dries and warms.
Blackened shoots in spring
- Frost
Late frost. Plants usually regrow (Illinois); cover them when frost is forecast.
Green tomato-like fruits
- Normal
The true fruit of the potato, not a cross with tomatoes. Don’t eat them (Iowa State, Illinois).
More problems with potatoes
Common pests
Wireworms
Click beetle larvae bore narrow holes in tubers, mainly in ground newly turned from grass (RHS).
Colorado potato beetle
In North America: striped adults and orange larvae strip the leaves. Hand-pick adults and crush yellow egg clusters under leaves (Utah State).
Flea beetles and leafhoppers
Flea beetles pit young leaves with tiny holes; leafhoppers brown the leaf edges (Illinois).
Potato cyst nematodes
Stunted plants and poor crops where potatoes and tomatoes have grown often. Rotate crops (RHS, Gardeners’ World).
More problems with potatoes
Common diseases
Late blight
Dark, water-soaked patches on leaves and stems spread fast in wet weather, then rot the tubers (Utah State). At the first sign, cut the foliage to the ground and lift the crop soon after: the potatoes are edible but won’t store (RHS, Gardeners’ World). Grow earlies or resistant varieties.
Common scab
Rough, corky patches on the skin. Worse in less acid soil and after heavy manuring (Clemson, Iowa State). Grow resistant varieties such as ‘Superior’.
Early blight
Dark target-like spots on older leaves; more common in North America than the UK. Water in the morning (Utah State, Gardeners’ World).
Blackleg
A bacterial black rot at the stem base, with stunted, yellowing plants (RHS). Certified seed reduces the risk.
Wilts and viruses
Yellowing, wilting or mottled plants. Use certified seed and rotate (Utah State).
Harvest & Use
Lift new potatoes as the plants flower, maincrops once the foliage dies back.
Harvesting potatoes
Scrape back a little soil to check tuber size before digging a whole plant (RHS).
New potatoes (earlies). When the flowers open or the buds drop, and the tubers are about the size of a hen’s egg (RHS): from June for first earlies, July for second earlies. Lift as needed; they don’t store.
Maincrops. From late August for eating fresh. For storing, wait until the foliage yellows and dies back, cut it off, and lift 10 to 14 days later so the skins set (RHS, UMD). The skin should no longer rub off (Iowa State).
How. Push the fork in at least 30 cm (1 ft) from the stem and lever the plant up (RHS). Lift on a dry day and leave the tubers on the surface for an hour or two to dry (Clemson, Gardeners’ World).
Yield. About 9 to 14 kg per 3 m row (20 to 30 lb per 10 ft) (Iowa State).
- Earlies: flowers open, tubers egg-sized.
- Maincrops: two weeks after the foliage dies.
- Fork in 30 cm (1 ft) from the stem.
Curing and storing potatoes
Eat new potatoes soon; Iowa State keeps them in the fridge for up to ten days. Maincrops store for months (RHS).
Cure unwashed maincrops for about two weeks at 10 to 16 °C (50 to 60 °F) in high humidity to heal nicks and thicken the skins (Iowa State, UMD).
Sort. Store only sound, dry tubers; use damaged ones first (RHS).
Store in the dark, in hessian or paper sacks, at about 4 to 7 °C (40 to 45 °F) (Utah State). Kept below about 3 °C (38 °F) they turn sweet; above 10 °C (50 °F) they sprout after two to three months (Iowa State). Never let them freeze.
Keep apart from apples and pears: their ethylene makes potatoes sprout (Utah State).
Check every few weeks for rot, and use them before spring (RHS).
Propagation
Why growers buy fresh seed potatoes each year.
Saving seed potatoes
Potatoes are grown from tubers, not true seed: the seed in the small green fruits doesn’t come true (UMD, Illinois).
Buy fresh certified seed each year. Saved tubers can carry viruses and diseases that build up over the years (Utah State, Clemson). The exception is an heirloom variety you can’t buy.
If you do save some, keep them somewhere cool and dark; they sprout in late winter and are planted like bought seed potatoes (Gardeners’ World).
More to Explore
Quick answers, guides that pair well with potatoes, and the sources behind this one.
Frequently asked questions
When should I plant potatoes?
In the UK from late March (earlies) to early May (maincrops); in the US two to three weeks before the last frost. See when to plant.
Do I need to chit seed potatoes?
No, but chitting earlies brings the crop forward a few weeks. See chitting.
How deep should I plant potatoes?
About 12 to 15 cm (5 to 6 in) deep in a trench; US guides range from 7.5 to 15 cm (3 to 6 in), and mulch methods plant at the surface. See planting.
Can I plant potatoes from the supermarket?
It isn’t worth it: they may carry disease or be treated against sprouting. Buy certified seed potatoes.
Why do I need to earth up potatoes?
It keeps tubers in the dark so they don’t turn green, and protects shoots from frost. See earthing up.
When are potatoes ready to harvest?
Earlies when the plants flower; maincrops for storing about two weeks after the foliage dies back. See harvesting.
Are green potatoes safe to eat?
Cut away small green patches; discard very green potatoes, which contain toxic solanine.
Can I grow potatoes in a bag?
Yes, earlies do well in a sack or pot at least 30 cm (12 in) wide and deep. See containers.
What are the green fruits on my potato plants?
The potato’s true fruit. They aren’t edible.
Related guides
Sources
- How to grow potatoes (opens in a new tab) Royal Horticultural Society
- Growing potatoes in the home garden (opens in a new tab) Iowa State University Extension and Outreach
- Potato (opens in a new tab) University of Illinois Extension
- Potatoes in the garden (opens in a new tab) Utah State University Extension
- Potato (opens in a new tab) Clemson Cooperative Extension
- Growing potatoes in a home garden (opens in a new tab) University of Maryland Extension
- How to grow potatoes (opens in a new tab) BBC Gardeners’ World