Tuber
How to grow potatoes
Solanum tuberosum
Chit seed potatoes from late January, then plant first earlies in mid to late March, second earlies in early April and maincrop in mid to late April, 10 to 15 cm deep. Earth up the shoots as they grow to protect them from frost and stop the tubers greening. Water well once tubers are forming, and choose blight-resistant varieties for maincrop if blight is a regular visitor.
- Hardiness
- Frost-tender foliage, earth up or fleece against late frost
- Position
- Full sun
- Soil
- Deep, fertile, loosened, slightly acid
- Ideal pH
- 5.0 to 6.0
- Water
- Moderate to high, most critical as tubers swell from flowering
- Feeding
- Heavy feeder
Sowing and planting potatoes
WhenChit Feb; plant Mar to Apr (earlies first); harvest Jun to Oct by type
Starting off
Grown from certified seed tubers, not seed. Chit in a cool, light, frost-free place from February, egg-box style, until the shoots are 2 to 3 cm and stubby. Plant from mid March when the soil is above 7 °C, earlies first, maincrops in April; cover shoots with soil or fleece against frost.
Spacing and planting
Earlies 30 cm apart in rows 60 cm apart; maincrops 38 cm apart in rows 75 cm apart. Plant 10 to 15 cm deep with the rose end (most sprouts) upward, then earth up to a 20 to 30 cm ridge. Earlies crop well in a 40 litre bag or 30 cm pot, three tubers to a bag.
Varieties worth growing
- Rocket
- First early, the fastest to a new potato, lifted from 10 weeks. Bland but worth it for June.
- Charlotte
- Second early salad potato, waxy and the best flavour of the group; also the best for bags and pots.
- Sarpo Mira
- Maincrop with the strongest blight resistance available, and slugs leave it alone. Floury, stores all winter.
- Desiree
- Red-skinned maincrop that stands drought and does well on heavy soil.
- Pink Fir Apple
- Late knobbly salad potato with a nutty flavour; the one worth the extra months.
Potatoes month by month
Timings are for central England. Allow two weeks later in the north and on cold, heavy soil.
- January
Order certified seed tubers; blight-resistant maincrop if you lost them last year.
- February
Chit in egg boxes in a cool, bright, frost-free room.
- March
Plant first earlies from mid month in the south once soil is above 7 °C. Plant bags under cover.
- April
Plant second earlies early in the month, maincrops from mid April. Earth up as shoots show.
- May
Earth up again. Fleece shoots on frosty nights.
- June
Lift first earlies once the flowers open. Water maincrops in dry spells.
- July
Lift second earlies. Start checking for blight after warm wet days.
- August
Keep maincrops watered as tubers swell. Cut haulm at the first blight sign.
- September
Cut maincrop haulm, wait two weeks, lift on a dry day, dry for two hours.
- October
Store in hessian sacks in the dark at 4 to 7 °C. Check monthly.
- November
Dig the empty bed and add compost for next year.
- December
Nothing to do. Eat them.
Feeding potatoes
Potash first, nitrogen second. Lush haulm is the sign you have overdone it.
A hungry crop: work in plenty of organic matter before planting and topdress with a balanced-to-high-potassium feed at earthing up.
Feeding plan
Planting, beds
100 g per metre of row scattered along the trench before the tubers go in.
First earthing up
Another 100 g per metre of row along the ridge, then earth over it.
Planting, bags and pots
5 to 7.5 g per litre of compost: 200 to 300 g mixed through a 40 litre bag, half at the bottom layer and half as you top up.
Flowering, maincrops only
20 to 50 g/m² along the row, watered in; lifts tuber size and skin quality.
Spring, light or acid soils
Kieserite (magnesium sulphate)
30 to 50 g/m² at earthing up if last year's lower leaves yellowed between the veins.
Signs to watch
Lower leaves pale with yellow between veins on light soil
Magnesium short
Kieserite or Epsom salts at earthing up
Corky, raised scabs on the skin
Not a nutrient fault but dry, limed soil
Keep moist and lower pH
Lush haulm with small, few tubers
Excess nitrogen
Earth up later and feed potash only
Pests, diseases and problems
Dark blotches on leaves with a pale halo, white fuzz underneath, haulm collapsing in a week
Late blight from June onwards in warm, wet weather
Grow earlies, which are lifted before it arrives, and Sarpo types for maincrop. Earth up well so spores cannot wash down to tubers. At the first sign cut the haulm to the ground and leave tubers two weeks before lifting.
Tunnels in the tubers at lifting
Slugs, mainly the small keeled slug that lives underground
Lift maincrops by early September rather than leaving them in, choose resistant varieties, and apply nematodes to the bed in July.
Narrow straight holes through tubers
Wireworm, worst in the first two years after grass
Grow earlies on new ground, cultivate the plot through winter so birds take the larvae, and avoid maincrops there until year three.
Corky raised scabs on the skin
Common scab on dry, limed or alkaline soil
Keep the soil moist for the six weeks after the tubers start to form, never lime before potatoes, and grow on the acid side.
Stunted yellow plants that wilt from the base, with a black rotting stem
Blackleg, carried on seed tubers
Buy certified seed, lift and bin affected plants, do not save your own seed from that bed.
Green patches on tubers
Light reaching the tubers
Earth up twice and keep bags topped up. Cut green parts off; they are mildly toxic.
Harvest and rotation
Harvest and storage
Earlies are ready 10 to 12 weeks from planting as the flowers open; maincrops at 18 to 20 weeks, once the haulm dies down. Fork from the side of the ridge and dry maincrops for 2 hours. A plant gives 1 to 1.5 kg of earlies or 2 to 3 kg of maincrop. Store maincrops in hessian sacks in a dark, frost-free shed at 4 to 7 °C.
Rotation and companions
Rotation: potato family (Solanaceae), 4-year gap, never beside or after tomatoes. Follow with brassicas, which like the broken, manured ground. Broad beans or peas sown alongside add nitrogen without competing; keep away from sunflowers and Jerusalem artichokes, which shade and compete for water.
Good to knowEarth up regularly to protect tubers from light and late frost; keep evenly moist as the tubers swell.
Growing potatoes in pots
Earlies and Charlotte are the ones to grow in bags. A 40 litre bag takes three chitted tubers on 10 cm of compost; cover with another 10 cm, then top up as shoots grow until the bag is full. Use a cheap peat-free multipurpose with the Potato Fertiliser mixed through it. Bags dry out faster than any bed: water until it runs from the base every two days in summer and daily in a heatwave, or the crop will be marbles. Tip the bag out on a sheet when the flowers fade; expect 1 to 1.5 kg per bag.
Potatoes: common questions
Do potatoes need high nitrogen?
No. Nitrogen grows haulm; potash grows tubers. A potato fertiliser has more potassium than nitrogen for that reason, and fresh manure at planting is the surest way to get a hedge of leaf and a handful of small potatoes.
When are potatoes ready to lift?
First earlies when the flowers open, about 10 to 12 weeks after planting. Maincrops when the haulm yellows and dies back, 18 to 20 weeks. Scrape a tuber with your thumb: if the skin stays put, it will store.
Can I plant potatoes from the supermarket?
You can, but they are often treated to stop sprouting and can carry blackleg and virus into your bed. Certified seed tubers are cheap insurance.
Sources
Growing information on this page was checked against these references in November 2026. Feeding rates are Dr Forest label rates.