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How to grow chilli peppers

chillis growing on bush
Image: Shutterstock/Kawephoto

January and February are the perfect months to turn up the heat and start sowing some fiery chilli peppers! Although you can still sow them right up until the end of April, early sowing gives your chilli peppers plenty of time to ripen before the end of summer. Here's how to grow a bumper crop of chilli seeds and plants.

Which chillies are the best?

With different degrees of heat, chillies can either add a little, or a lot, of spice to your dishes
Image: Chilli Pepper 'Heatwave' (hot!) by Thompson & Morgan

Chillies contain a chemical called capsaicin that stimulates the nerve endings in your mucous membranes; that's what makes the hot taste you feel when you bite into one. The variety, the maturity of the plant and the local growing conditions determine how hot your chillies will be.

Whether you like your peppers sizzling or just a little warm, the range of of chillies from which you can choose is bigger than ever. Try planting a few different varieties to find the one that suits you.

Which chilli variety should you plant?

tropical heat chilli collection
Put your tastebuds to the ultimate test with Thompson and Morgan's 'Tropical Heat' variety seed pack, containing Scotch Bonnet and Habaneros
Image: Chilli Pepper 'Tropical Heat' Variety

Not sure which is the best chilli to grow? Have a look at this quick list to find out which are just hot, and which will send your tastebuds into meltdown.

Bishops Crownmild
Summer Heat(Jalapeno)hot
Chilli Pepper 'Heatwavehot
Joe's Longhot
Tabascovery hot
Demon Redvery hot
Tropical Heatscorching
Prairie Firescorching
Naga JolokiaAtomic!

Fun fact: The Scoville Scale is the traditional measure for chilli heat. In 2017, Welsh fruit grower Mike Smith accidentally grew the world's hottest chilli. At 2.48 million on the Scoville scale, his creation, Dragon's Breath, pushed the 2.2 million unit Carolina Reaper into second place. According to the Daily Telegraph, experts say just one of Mike's chillies would be enough to trigger anaphylactic shock.

How to grow chillies from seed

propagating chilli plants from seed
To reach maximum growth (and spiciness) chillies need plenty of warmth.
Image: Shutterstock/Jiri Foltyn

For the best and hottest chillies, start sowing indoors as early as January (although if there are late frosts, you can in some years get away with sowing in March) - the hottest varieties often need the longest growing period. Chillies need plenty of warmth to germinate so invest in a heated propagator for the windowsill or use a warm airing cupboard.

Sow Chilli pepper seeds on the surface of a moist, free-draining, seed compost and cover with a fine sprinkling of compost or vermiculite. Place seed trays in a propagator at a temperature of 18-25C (64-77F). If you don't have a propagator, use polythene to cover your seed trays.

Germination usually takes 7-10 days, after which you can move your seedlings to a warm, sunny windowsill or a heated greenhouse. Keep the compost evenly moist but take care not to let it get soaking wet.

Transplanting chilli pepper plants

transplanting chilli plants
When they are big enough, transplant chillis into larger pots until the risk of frost has passed
Image: Shutterstock/Marsan

When your chilli seedlings are big enough to handle without breaking, transplant them into individual 7.5cm (3") pots of compost and grow them on until all risk of frost has passed, and they are large enough to be transplanted to their final positions. From an early sowing, this will normally be from May onwards.

Grow chillies individually, transplanting them into 2 litre containers, or plant them in grow bags allowing three plants per bag. Place pots or growbags under cover in a warm greenhouse, conservatory, or polytunnel.

Alternatively, plant your chillies outside in a sunny, sheltered spot. Gradually acclimatise your plants to outdoor conditions over a period of 7 to 10 days before transplanting them into well prepared beds of fertile, moist, well-drained soil. Space chilli pepper plants 50cm (20") apart. Short of space? Try growing them indoors on a sunny windowsill.

How to grow on chilli pepper plants

growing on chilli plants
Remember to water chillies regularly and use a high potash tomato fertiliser to get the best harvest
Image: Shutterstock/Victority

Water chilli pepper plants regularly throughout the growing season, and once the first fruits have set, feed them weekly with a high potash tomato fertiliser. Also remember to:

  • • Pinch out the growing tip of the first flowering shoots to promote more branching and a better harvest.

  • • Water regularly but sparingly. It's best to keep your soil a little on the dry side because slightly stressing your chilli plants helps to produce hotter peppers. Taller varieties of chilli pepper may require staking.

  • • Add a thick mulch of organic matter around the base of the plants to help conserve moisture and suppress weed growth.

Growing chillies indoors? Do remember to open windows and doors to provide insects access to the flowers to ensure good pollination. Alternatively, hand pollinate the chillies by moving from flower to flower, tickling the centre of each with a fine artist's paint brush.

Harvesting chillies

harvested summer heat chillies
Make sure you harvest your chillies before the colder months. If they have yet to ripen, bring them indoors
Image: Chilli Pepper 'Summer Heat' F1 Hybrid from Thompson and Morgan

Chillies require warmth and long sunny days to ripen properly. From an early sowing, this shouldn't be a problem, but later sowings in the UK may leave your peppers feeling the cold as summer days begin to shorten.

If your crop has yet to ripen, bring your plants indoors and let them ripen on a warm sunny windowsill. Harvest chillies singly by cutting them from the plant with secateurs. Chilli peppers grown outdoors must be harvested before the first frost.

How do you store chillies?

dried chillies
By drying or freezing your chillies, you can preserve their taste
Image: Shutterstock/Mr Aesthetics

To preserve your chillies, either dry them or freeze them:

  • Dry chilli peppers: Take a needle and thread the stems of the chilli peppers together so that they form a "daisy chain" of peppers, then hang them in a warm, well ventilated spot and let the air dry them over a 4 to 5 week period.

  • Freeze chilli peppers: Freeze chillies in freezer bags straight after picking, without any further preparation. After you defrost your chillies, you'll find the flesh slightly softened, but don't worry, they'll taste just as fiery as they did when you picked them.

For a few more top chilli growing ideas, check out the video below:

What are your top chilli tips? Let us know on our Facebook page - and if you have pictures of your crop, share away!

Sue Sanderson T&M horticulturalist

Written by: Sue Sanderson

Plants and gardens have always been a big part of my life. I can remember helping my Dad to prick out seedlings, even before I could see over the top of the potting bench. As an adult, I trained at Writtle College where I received my degree, BSc. (Hons) Horticulture. After working in a specialist plantsman's nursery, and later, as a consulting arboriculturalist, I joined Thompson & Morgan in 2008. Initially looking after the grounds and coordinating the plant trials, I now support the web team offering horticultural advice online.


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