How to Grow Chilli Peppers in the UK

Grow chillies in a greenhouse, polytunnel, conservatory or a sunny, sheltered spot. Sow early so they get a long, warm season, pot them on as they grow and feed once the flowers appear. Then get ready for a colourful, spicy harvest.

The RHS chilli growing guide suggests growing under cover for the best crop, and only planting outside once nights stay above 12°C. This guide covers varieties, sowing, potting on, feeding, ripening and the common slip-ups. If you’re new to it, read how to sow seeds indoors too.

Which chilli varieties to grow in the UK

Picking the right variety is the biggest decision you’ll make. It decides how hot your chillies are, how long they take, and whether you can grow them outside or need a greenhouse.

New to chillies? Start with mild or medium ones. They’re more forgiving, ripen faster and crop more heavily here. Try the superhots once you’ve a season under your belt. Grafted vegetable plants are worth a look too, as they give slow superhots a stronger root system.

Mild chillies

• Padron: the Spanish tapas chilli. Mostly mild when picked small and green, with the odd hot one. Crops loads. Can ripen outdoors in southern England.
• Hungarian Hot Wax: banana-shaped, thick-walled fruit that’s great for stuffing and roasting. Ripens from yellow to red. A good outdoor choice.
• Anaheim: big, mild fruit with thick flesh. Lovely stuffed or roasted whole. Grows well in a greenhouse.

Medium chillies

• Jalapeno: the world’s favourite. Thick-walled fruit about 7-8cm long. Pick green, or leave to turn red for more heat. Crops well in a greenhouse.
• Cayenne: long, thin fruit that dries really well. Classic heat for curries and sauces.
• Serrano: hotter than Jalapeno, with thin walls that are perfect for salsa. A compact plant for pots and small greenhouses.

Hot chillies

• Scotch Bonnet: fruity and tropical, a must for Caribbean cooking. Needs a warm greenhouse.
• Habanero: a close cousin of Scotch Bonnet with intense, fruity heat. Comes in orange, red and chocolate. Needs steady warmth to ripen.
• Bird’s Eye: small, upright fruit that packs a punch. The compact plant suits a sunny windowsill.

Superhot chillies

• Carolina Reaper: red, wrinkled fruit with a pointy tail and ferocious heat. Needs a long season and a heated greenhouse.
• Trinidad Scorpion: pointed, wrinkled fruit with an intense, slow-building heat. A slightly shorter season than the Reaper.
• Komodo Dragon: starts off deceptively mild before the heat builds. Popular with British growers.

Chilli varieties compared

Heat is rated in Scoville Heat Units (SHU), but you only need a rough idea of how hot each one is.

How to sow chilli seeds indoors

Start early. January to February is the best time for most UK growers. Chillies need a long season, and sowing late is the most common reason for a poor crop. Our January planting guide has other indoor sowings to do at the same time. For general tips, see our guide on how to sow seeds indoors.

What you’ll need

• Seed trays or small 7cm pots
• A heat mat or heated propagator
• Seed compost
• Clear lids or cling film
• Labels and a pen
• A spray bottle for misting

Step-by-step sowing

1. Fill 7cm pots or module trays with seed compost. Firm gently and water until evenly moist.
2. Sow two or three seeds per pot, 5mm deep, and cover with a thin layer of vermiculite.
3. Stand them on a heat mat set to about 25°C and cover with a clear lid to keep them humid.
4. Keep the compost moist but not soggy. Mist rather than pouring water on.
5. Most seedlings appear in two to three weeks. Superhots can take a month or more.
6. Once they’re up, take off the lid but leave them on the heat for another week.
7. Move them to a bright windowsill or under grow lights once the first true leaves appear.

Bottom heat really matters. A cold winter windowsill is far too chilly for chilli seed, and without heat they’ll be slow and patchy.

Potting on and growing strong plants

Pot seedlings on when their roots fill the pot. You’ll see roots poking out of the drainage holes, or you can gently tip the plant out to check. This usually happens twice.

First potting on (March)

Move seedlings from 7cm pots into 9cm pots of multipurpose compost. Hold them by a leaf, never the stem. Water well and put them back somewhere warm and bright.

Once a plant has six to eight pairs of leaves, you can pinch out the growing tip. This makes it bushier, with more flowering stems and so more chillies. Some growers skip it, as pinched plants ripen a little later.

Second potting on (April to May)

Move into the final pot: 3-5 litres for compact varieties, and 7-10 litres for big plants like Habanero and Scotch Bonnet. Use peat-free multipurpose compost with some perlite mixed in for drainage.

In a greenhouse border, space plants 45-60cm apart. Dig in well-rotted compost the autumn before. Plants in the border have more root room and need watering less often than pots.

Hardening off and growing outdoors

If your chillies are going outside, harden them off over 10-14 days first. Start with a few hours a day in a sheltered spot and build up until they’re out day and night.

Only plant out after the last frost, usually late May in southern England and early June further north. Nights need to stay above about 12°C. Cold nights stop growth and can damage flowers.

Best spots outdoors

• A south-facing wall or fence: it soaks up heat in the day and gives it back at night.
• A sheltered patio: out of the wind, which dries leaves and knocks flowers off.
• Raised beds: they warm up faster than the ground and drain well.

Outdoors works best for mild and medium chillies in southern England. Padron, Jalapeno and Hungarian Hot Wax are your best bets in a warm summer. Hot and superhot types need the steady warmth of a greenhouse or conservatory.

Handy tip: Black pots soak up more sun than terracotta or pale pots, so they keep outdoor chilli roots a bit warmer.

Mild and medium types are the best bet outdoors. A sunny wall and dark pots keep the roots that bit warmer on cooler nights.

Growing chillies under cover

Greenhouses, polytunnels and conservatories give the best chilli crops in the UK. They’re warmer, keep off wind and rain, and stretch the season at both ends. If you’re starting a vegetable garden, a greenhouse opens up the whole range of chillies. Wondering if one’s worth it? Our guide on whether you need a greenhouse weighs it up.

Greenhouse tips

• Open the vents on hot days. Chillies stop setting fruit when it gets really hot.
• Water daily in summer, as pots in a greenhouse dry out fast.
• Mist the leaves on hot mornings to help the flowers set.
• Open doors and vents so insects can pollinate, or tap the flowering stems gently to shake the pollen about.
• Use fleece or a small heater on cold nights early and late in the season. Our greenhouse heating guide compares the options.

On a windowsill

Compact varieties like Apache, Prairie Fire and Basket of Fire grow well on a sunny south-facing windowsill. Use a pot of at least 3 litres and turn it daily so the plant doesn’t lean. You’ll get a smaller crop than in a greenhouse, but it’s right there by the kitchen.

Feeding chilli plants

Chillies get hungry once they start flowering, and the right feed makes a big difference.

Before flowering

Feed every fortnight with a balanced liquid feed from the first potting on. This builds strong leaves and stems. Don’t overdo the nitrogen, or you’ll get big leafy plants with few flowers.

Once flowers appear

Switch to a high-potash feed, such as tomato feed. Give it every week at the rate on the bottle. This helps flowers and fruit develop. It’s the same routine as for growing tomatoes.

Spotting feeding problems

Watering

Water chillies regularly. Uneven watering makes flowers drop before they set fruit. In hot weather, greenhouse chillies in pots may need watering once or twice a day. Poke a finger in the compost: if the top 2cm is dry, water until it runs from the base.

Chilli growing calendar month by month

For the full greenhouse sowing plan, see our best greenhouse plants month by month guide.

How to ripen green chillies

Every chilli starts green and changes colour as it ripens, to red, orange, yellow, chocolate or purple depending on the variety. Ripe chillies are hotter and tastier than green ones. Jalapeno and Padron are often picked green, but they’re still good with a bit of colour.

Speeding up ripening

• Move plants to the warmest spot you have in September and October.
• Keep watering steadily so plants stay healthy while the fruit colours.
• Pinch off new flowers in September, so the plant puts its energy into the fruit it has.
• Pick a few fruit, which helps the plant ripen the rest.

Ripening picked fruit indoors

If frost is on the way and you still have green chillies, pick them all. Put them on a sunny windowsill with a ripe banana nearby, which helps them colour. Bigger fruit will ripen over a week or few, but very small ones won’t ripen off the plant.

Overwintering chilli plants

Chillies are perennials in their tropical home. Here, healthy plants can be kept indoors over winter and may start growing earlier than new plants. Results vary with the variety, how much light and warmth you can give them, and pests.

How to overwinter

1. Pick all the fruit in October, green ones included.
2. Cut the stems back to 15-20cm and remove the leaves.
3. Water very little, just every few weeks to stop the compost drying right out.
4. Keep them bright and above 10°C, such as a cool spare room, frost-free porch or heated greenhouse.
5. Look for new shoots in February or March. When they appear, water more and start feeding again.
6. Refresh the compost in March by scraping off the top few centimetres and topping up with fresh.

Some varieties come through winter better than others. Habanero, Scotch Bonnet and Rocoto usually do well. Others are simpler to just grow fresh from seed each year.

Handy tip: Label your overwintered plants. By March, a cut-back chilli looks just like a dead twig, and it’s easy to throw out a perfectly healthy plant.

Cut back to 15 to 20cm, keep them bright and above 10C, and water only now and then. By March they look like twigs, so label them before they get thrown out.

Growing chillies in pots

Chillies love pots. They have compact roots and don’t need deep soil. Plenty of gardeners with big gardens still grow all their chillies in pots.

Pot sizes

Use peat-free multipurpose compost with some perlite mixed in. Chillies hate soggy roots, so make sure every pot has drainage holes, and stand pots on feet or gravel.

Where to put them

Put pots in the sunniest spot you have. South-facing walls, patios and greenhouse benches all work. Grouping pots together makes a cosy, warmer patch. Water daily in summer and give a weekly tomato feed once flowering starts.

Drying and preserving chillies

A good chilli year gives you far more than you can eat fresh. Drying, freezing and making sauces are the best ways to keep them.

Air drying

Thin-walled varieties like Cayenne, Bird’s Eye and Thai chillies air-dry well. Thread them onto string through the stalks and hang them somewhere warm and airy. They take a few weeks. When they snap cleanly, they’re done. Store them in airtight jars away from the light.

Thick-walled varieties like Jalapeno and Habanero tend to rot before they dry, so use a dehydrator or the oven instead.

Thin-walled types like cayenne and bird’s eye air-dry well on a string. Wear gloves for the hot ones, and keep your hands away from your eyes.

Oven drying

Halve the chillies lengthways and lay them cut-side down on a lined baking tray. Dry on the lowest oven setting with the door slightly open, checking every hour. They’re done when brittle and papery, which can take several hours.

Freezing

Freezing is the easiest way. Wash and dry the chillies, then freeze them whole in labelled bags. No blanching needed. They grate easily from frozen, which is handy for adding just a little heat.

Making chilli flakes

Dry the chillies completely, then crush them with a pestle and mortar or blitz them in a spice grinder. Wear gloves for the hottest ones. Store in small jars.

Watch out: Wear gloves when handling hot chillies, especially Habanero and hotter. The oil sticks to your skin and burns. Don’t touch your face or eyes afterwards.

Common mistakes when growing chillies

Sowing too late

Lots of people sow chillies in March or April along with tomatoes. But chillies need longer. Sow in January or February so they have time to flower and ripen. Late-sown plants can end the season covered in green fruit that never colours.

No bottom heat

Chilli seed needs real warmth to sprout, and a normal room is often too cool. A heat mat or heated propagator makes a huge difference.

Overwatering seedlings

Young chilli seedlings rot easily in soggy compost. Let the surface dry a little between waterings, and mist rather than pour.

Too much nitrogen

Nitrogen-rich feed gives tall, leafy plants with dark green leaves and very few flowers. Switch to tomato feed as soon as flowering starts.

Leaving every fruit to ripen

If you leave every chilli to turn red, the plant slows down making new flowers. Pick some green to keep it producing, and let others ripen fully.

Now you’ve mastered chilli peppers, read our guide on growing tomatoes in the UK. They like the same warm conditions and the same tomato feed. If you grow chillies for Indian cooking, our grow Indian and Eastern spices in the UK guide covers Pusa Jwala, Kashmiri and Bhut Jolokia, alongside turmeric, ginger, curry leaf and the rest of the curry cupboard.

Frequently asked questions

When should I sow chilli seeds in the UK?

Sow indoors from mid-January to late February. Starting early gives plants time to flower and ripen before autumn turns cold. Use a heated propagator or a heat mat with a thermostat for steady warmth.

Can I grow chillies outdoors in the UK?

Mild varieties can, in a sheltered, sunny spot. Padron, Jalapeno and Hungarian Hot Wax can ripen outside in southern England in a warm summer. Further north, or for hotter varieties, use a greenhouse, polytunnel or sunny conservatory.

How long do chilli seeds take to germinate?

Usually two to three weeks with bottom heat. Very hot types like Carolina Reaper can take a month or more. Without bottom heat, they’re slow and many may not come up at all.

Why are my chilli plants not producing fruit?

Usually because it’s too cold. Chillies need steady warmth to set fruit. Too much nitrogen feed, poor pollination and not enough light can also be to blame. Indoors, tap the flowering stems gently to help spread the pollen.

How do I make chillies ripen faster?

Move plants to the warmest, brightest spot you have. Pinch off new flowers in September, keep watering steadily and pick fruit as it colours.