Fruiting vegetable
How to grow sweet peppers
Capsicum annuum
Sweet peppers need a long, warm season, so in the UK they do best in a greenhouse, polytunnel or conservatory, or in a pot against a south-facing wall. Sow in late February or March at 20 to 25 °C, grow the plants on in good light without a check, and move them to 25 to 30 cm pots in May. Keep the compost evenly moist and feed from the first flowers. Fruit is ready green from July and coloured two to three weeks later.
- Hardiness
- Tender, needs 18 to 21°C to crop well
- Position
- Full sun, warm/sheltered or under glass
- Soil
- Rich, free-draining
- Ideal pH
- 6.0 to 6.8
- Water
- Moderate to high, even moisture
- Feeding
- Heavy feeder
Sowing and planting sweet peppers
WhenSow Feb to Mar with heat; pot on Apr to May; plant out under glass May; harvest Jul to Oct
Starting off
Sow indoors in late February to March, 0.5 to 1 cm deep at 20 to 25 °C in a heated propagator, germinating in 10 to 21 days; seedlings need light and 18 °C or they stall. Prick out into 9 cm pots, pot on to 12 cm in April, and plant under glass in May or outdoors in June after 12 °C nights.
Spacing and planting
Plant 45 to 50 cm apart in a greenhouse border or one per 25 to 30 cm pot or three per growbag; outdoors 40 cm apart against a warm wall. Plant at the same depth as the pot and stake with a 60 cm cane. Fine in a 25 to 30 cm pot on a sunny patio.
Varieties worth growing
- Bell Boy F1
- A dependable blocky bell pepper, green ripening to red, that sets well in an unheated greenhouse.
- Gypsy F1
- Early, tapered fruit turning from yellow-green to orange-red. It ripens in a poor summer when the big bells stay green.
- Corno di Toro Rosso
- Long bull's horn pepper, thinner walled and sweeter than a bell, excellent for roasting and quicker to colour.
- California Wonder
- The classic thick-walled bell for stuffing. It needs the longest season, so sow it in February and keep it under glass.
- Mohawk F1
- A compact, spreading plant with small orange fruit, bred for patio pots and hanging baskets.
Sweet peppers month by month
Timings are for central England. Allow two weeks later in the north and on cold, heavy soil.
- January
Nothing to do. Order seed.
- February
Sow in the last fortnight in a heated propagator.
- March
Sow by mid month. Prick out into 9 cm pots once the seed leaves are flat. Keep at 18 °C in full light.
- April
Pot on to 12 cm pots. Keep plants warm at night.
- May
Move to final 25 to 30 cm pots under glass and stake. Pinch out the tip at about 30 cm tall to make the plant branch.
- June
Plants for outdoors go out after hardening off. Start feeding at the first flowers. Shade the greenhouse.
- July
Cut the first green fruits to keep more coming. Feed every two to four weeks and water daily.
- August
Main harvest. Tie in heavy branches. Leave some fruit to colour.
- September
Last feed early in the month. Bring outdoor pots under cover before cold nights.
- October
Pick everything before the first frost; full-size green fruit will colour on a windowsill. Clear the plants.
- November
Nothing to do.
- December
Nothing to do.
Feeding sweet peppers
Peppers want a steady, moderate supply with potassium ahead of nitrogen once they flower. Too much nitrogen early gives a big dark plant that drops its flowers.
A balanced feed early, then a high-potassium feed once flowering and fruiting.
Feeding plan
Final potting, May
Chilli & Pepper Fertiliser 3-3.5-7
5 g per litre of compost, mixed through: 50 g for a 25 cm pot of about 10 litres, 75 g for a 30 cm pot of about 15 litres.
Final potting, optional
1 g per litre of compost: 10 g for a 10 litre pot. It adds calcium and magnesium to the compost, but it will not cure blossom end rot caused by pots drying out.
From the first flowers, every 2 to 4 weeks until early September
Chilli & Pepper Fertiliser 3-3.5-7
1 to 3 g per litre of pot volume scattered on the surface and watered in: 10 to 30 g for a 10 litre pot. Start at the low end and step up once fruit is swelling.
Greenhouse border, before planting
Fruit & Vegetable Fertiliser 4-5-6
The pepper feed carries no bed rate on its label, so use the 4-5-6 at 100 g/m²: about 25 g per plant at 50 cm spacing (100 x 0.25 m²).
Only if older leaves yellow between the veins
Kieserite (magnesium sulphate)
2 g per litre of water as a root drench, repeated once after three weeks if needed.
Signs to watch
Sunken, leathery black patch on the fruit base
Blossom-end rot from erratic watering, not a calcium shortage
Water evenly, never letting pots dry
Older leaves yellow between the veins
Magnesium locked out by high-potash feeding
Epsom salts spray fortnightly
Lush, dark plants dropping flowers
Excess nitrogen or heat over 30 °C
High-potash feed, ventilate
Pests, diseases and problems
Clusters of green insects on shoot tips and under young leaves; leaves sticky and curled
Aphids, which multiply fast under glass from April
Rub them off by hand as soon as they appear, or rinse the plant with water. In a greenhouse introduce the parasitic wasp Aphidius, and leave the vents open for hoverflies and ladybirds.
Leaves finely mottled pale and dull, with webbing in bad cases
Glasshouse red spider mite in hot, dry air
Damp down the floor and mist the plants daily in hot weather. Introduce the predatory mite Phytoseiulus persimilis early.
Small white flies under the leaves that rise in a cloud when disturbed
Glasshouse whitefly
Yellow sticky traps for early warning, then the parasitic wasp Encarsia formosa while numbers are still low.
Grey furry mould on fruit, stems or fallen petals in late summer and autumn
Grey mould (botrytis) in cool, still, damp air
Ventilate every day, water in the morning, clear fallen flowers and leaves and cut out affected parts into clean tissue.
Pale, papery, sunken patch on the side of the fruit facing the glass
Sun scald
Shade the greenhouse from June with netting or shade paint and keep enough leaf over the fruit. Affected peppers are fine to eat once trimmed.
Harvest and rotation
Harvest and storage
Cut green fruit at full size, 18 to 20 weeks from sowing, or leave 2 to 3 weeks more to turn red, yellow or orange for sweetness; cut with 2 cm of stalk using secateurs rather than pulling. A plant gives 6 to 10 fruits under glass, 3 to 5 outdoors. They keep 2 weeks in the fridge; roast and freeze, or dry slices for stock.
Rotation and companions
Rotation: potato family (Solanaceae) with tomatoes and aubergines, 3 to 4 year gap outdoors; use fresh compost in greenhouse pots each year. Keep away from fennel, which inhibits growth, and from brassicas, which want cooler, limed ground.
Good to knowNeeds warmth, best under glass in the UK; pinch the growing tip to make the plant bush out.
Growing sweet peppers in pots
A pot is the best way to grow peppers in Britain, because it can follow the warmth: greenhouse in May, patio in July, back under cover in September. Use a 25 to 30 cm pot (10 to 15 litres) of peat-free multipurpose compost for each plant, with a 60 cm cane. Black pots warm the roots, which peppers like. Water every day in summer and do not let the pot swing between dry and soaked, as that is what causes blossom end rot. Compact varieties such as Mohawk F1 manage in a 20 cm pot.
Sweet peppers: common questions
Can you grow sweet peppers outside in the UK?
Yes in a warm summer, but only in the sunniest, most sheltered spot you have, and the crop will be about half what you get under glass. Plant out in June once nights stay above 12 °C, choose an early variety such as Gypsy F1, and grow in pots so you can bring them in to finish ripening.
Why are my peppers not turning red?
They need more time and warmth: a full-size green pepper takes another two to three weeks to colour, longer once nights cool. Leave the fruit on the plant, keep the greenhouse closed at night in September, and pick a few green ones so the plant can ripen the rest.
Should I pinch out sweet pepper plants?
Pinching out the growing tip at about 30 cm tall gives a bushier plant with more fruiting branches, and is worth doing on plants sown in February. On late sowings leave the tip alone, since pinching delays the first fruit by a week or two.
Sources
Growing information on this page was checked against these references in November 2026. Feeding rates are Dr Forest label rates.
- How to grow sweet peppersRHS
- How to grow sweet peppers from seedBBC Gardeners' World