Peppers (sweet peppers and chillies) are rewarding crops for UK gardeners, offering colourful, flavourful fruits throughout summer and autumn. While they need warmth and protection, growing peppers in a greenhouse, polytunnel, or sunny windowsill is straightforward and productive. I start mine in a heated propagator on top of the airing cupboard every February — without that consistent bottom warmth, peppers sulk for weeks and never really catch up.
Not sure when to sow? See our When to Plant Peppers UK →
Founder & Head Grower, SoilCommander · RHS Level 2 · 12+ years growing in Yorkshire
I've been growing vegetables on my Yorkshire allotment and raised beds since 2012. Everything I write is based on what I've actually grown, failed at, and eventually got right in a real UK climate.
Watch this step-by-step guide to growing bell peppers at home in the UK — from seed to a full harvest of sweet, colourful fruits on your windowsill or in the greenhouse.
🌶️ Did you know? Bell peppers start green and ripen to red, yellow, or orange — the longer you leave them, the sweeter and more nutritious they become.
Quick Growing Facts
- Sowing Time: February to April indoors
- Harvest Time: July to October
- Growing Time: 20-30 weeks from sowing to first harvest
- Difficulty: Moderate
- Position: Greenhouse, polytunnel, or very warm, sheltered spot outdoors — the RHS notes peppers need temperatures consistently above 15°C, so most UK crops do best under glass
When to Sow Peppers
- Indoor sowing: February-April in a heated propagator or warm windowsill
- Early sowings: February-March for greenhouse growing (need 18-21°C)
- Later sowings: March-April for outdoor growing in very warm, sheltered locations
- Chillies: Sow in February as they need an even longer season than sweet peppers
Soil and Compost Preparation
- Container growing: Use good quality multipurpose or tomato compost
- Greenhouse borders: Enrich soil with well-rotted manure or compost
- Drainage: Ensure excellent drainage; peppers hate waterlogged conditions
- pH level: Slightly acidic to neutral (pH 6.0-7.0)
- Pot size: Final pot size should be at least 7.5-10 litres (2-3 gallons)
How to Sow Peppers
- Use small pots or modules: Fill with seed compost
- Sow on surface: Place 2-3 seeds per pot on the surface
- Cover lightly: Cover with a thin layer of vermiculite or sieved compost
- Warmth essential: Keep at 18-21°C (65-70°F) for germination
- Use a propagator: A heated propagator speeds germination (10-21 days)
- Good light: Move to bright, warm location once germinated
- Thin to strongest: Remove weaker seedlings, leaving one per pot
💡 Top Tip
Pepper seeds germinate best with bottom heat. Place seed trays on top of a refrigerator, near a radiator, or use a heated propagator to maintain consistent warmth for faster, more reliable germination.
Potting On and Planting Out
- First potting: Move to 7.5cm (3 inch) pots when 2-3 true leaves appear
- Final potting: Transfer to final 7.5-10 litre pots when roots fill smaller pots
- Greenhouse planting: Plant in greenhouse borders or large pots in late April-May
- Outdoor planting: Only in very warm, sheltered spots after all frost risk (early June)
- Harden off thoroughly: Acclimatise to outdoor conditions over 2-3 weeks
- Spacing: Space plants 45cm (18 inches) apart
Discover how to grow capsicum (bell peppers) at home in the UK — practical tips on pots, compost, watering, and getting a great harvest from your own garden or windowsill.
🫑 Did you know? Capsicum plants are perennials in warm climates — in the UK, you can overwinter them indoors and get a head start on next year's crop.
Ongoing Care
- Watering: Keep compost consistently moist but not waterlogged; water regularly, especially when fruiting
- Feeding: Feed weekly with high-potash tomato fertiliser once first fruits appear
- Support: Stake tall varieties to prevent stems breaking under fruit weight
- Pinching out: Pinch out growing tip when plants reach 30cm (12 inches) to encourage bushier growth
- Temperature: Maintain 18-25°C for best growth; provide shade if over 30°C
- Humidity: Mist plants occasionally in hot weather to aid fruit set
Common Problems
Blossom end rot: Dark patches on fruit base caused by calcium deficiency due to irregular watering. Maintain consistent moisture levels.
Poor fruit set: Often due to temperatures too high or too low. Maintain 18-25°C and ensure good pollination by gently shaking plants.
Aphids: Small sap-sucking insects. Spray with soapy water or use biological controls.
Red spider mite: Tiny mites causing yellowing leaves. Increase humidity and use biological controls.
Harvesting Peppers
- Green peppers: Harvest when full-sized but still green (12-16 weeks after planting out)
- Coloured peppers: Leave to ripen to red, yellow, orange, or purple (2-3 weeks longer)
- Ripe = sweeter: Coloured peppers are sweeter and more nutritious than green
- Cut, don't pull: Use secateurs or scissors to cut fruits with a short stem
- Regular picking: Harvest regularly to encourage more fruit production
- Before frost: Harvest all fruits before first frost; green ones will ripen indoors
Storage
- Fresh: Store in the refrigerator for up to 2 weeks
- Room temperature: Green peppers will ripen to red if kept in a warm place
- Freezing: Chop and freeze raw for up to 6 months (texture changes but fine for cooking)
- Drying: Thread chillies on string and hang in a warm, dry place
- Preserving: Roast and preserve in oil, or make into chutney or hot sauce
Recommended Varieties
Sweet Peppers
Mohawk
F1 hybrid, early and reliable — good choice if your season under glass is shorter. Turns from green to red.
Gypsy
Very productive F1 hybrid with sweet, pointed fruits — a strong all-rounder for UK greenhouses.
California Wonder
The classic thick-walled blocky pepper — reliable cropper if you want the traditional bell shape.
Redskin
Compact habit makes it ideal for containers and small greenhouses; ripens earlier than most.
Chilli Peppers
Apache
Compact and very productive with medium heat — a reliable choice for windowsills and small spaces.
Hungarian Hot Wax
Mild to medium heat with banana-shaped fruits, good for gardeners who want flavour without intense heat.
Jalapeno
Classic medium-heat chilli, dependable cropper, and the most useful all-purpose variety in the kitchen.
Essential Tools & Supplies
Sweet peppers and chillies are the same species — the heat comes entirely from capsaicin levels, which the plant produces more of under stress such as dry soil or temperature swings. Keeping chillies consistently watered actually makes them slightly milder.
Frequently Asked Questions
Why are my pepper plants not flowering?
Usually temperature — peppers need 18-25°C to flower and set fruit reliably. Below 15°C or above 30°C, flowering slows or stops. Check ventilation in hot greenhouses and consider extra warmth in cool spells.
Can I grow peppers outdoors in the UK?
Only in the warmest, most sheltered spots, and mainly in the South. Most UK gardeners get far more reliable harvests growing peppers in a greenhouse, polytunnel, or on a sunny windowsill.
Why do my chillies taste milder than expected?
Consistent watering and feeding tend to produce milder fruit, since heat increases under stress. For hotter chillies, let the compost dry out slightly between waterings in the final few weeks before harvest.
Can I keep a pepper plant for a second year?
Yes — peppers are short-lived perennials. Bring container-grown plants indoors before frost, cut back hard, and keep on a bright windowsill over winter. They'll often crop earlier and more heavily the following year.
Do I need to hand-pollinate peppers under glass?
It helps. Pepper flowers are self-fertile but benefit from a gentle shake or a soft brush dabbed between flowers, especially in a greenhouse where wind and insect activity are limited.
Plan Your Vegetable Garden
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Get the Planner — £19 →Turn your kitchen windowsill into a productive pepper farm — this short guide shows how to grow chillies and sweet peppers indoors in the UK with minimal space and maximum yield.
🌿 Did you know? Pepper plants grown on a sunny UK windowsill can produce dozens of fruits per season — and overwintered plants often crop even more heavily the following year.
Tools That Help With This Crop
Use these links when the guide moves from reading into sowing, planting, watering, and keeping the crop healthy.
Plan the next step
Use the printable UK Vegetable Garden Planner to turn this guide into sowing dates, bed layouts, and weekly garden tasks.