RHS Growing Guides

How to grow chilli peppers

Our detailed growing guide will help you with each step in successfully growing Chilli Peppers.

  1. Getting Started
  2. Choosing
  3. Sowing
  4. Planting
  5. Plant Care
  6. Pruning and Training
  7. Harvesting
  8. Storing
  9. Problems
1

Getting Started

Getting Started
Choosing
Section 1 of 9

Growing your own chillies means you can enjoy a huge array of colours, shapes, flavours and levels of heat – a much wider range than you could ever buy in supermarkets. These tender plants grow best in a greenhouse, but can also be grown outdoors in a sunny spot, in pots or in the ground.

There’s a wide array of chillies to choose from if you grow your own from seed
Chillies (Capsicum) are tender plants that need heat, humidity and lots of sunshine to fruit well. Closely related to sweet peppers, they make attractive plants with their colourful, glossy fruits. They grow well in containers and take up little space, with compact varieties reaching only 20–30cm (8–12in) tall. This makes it easy to grow several different varieties, even when space is tight. For the best crop, grow them in a greenhouse, polytunnel or sunny conservatory. They should also be happy in a sheltered, sun-baked spot outdoors – ideally beside a south-facing wall or on a sunny patio or balcony. They generally like similar growing conditions to tomatoes, so are ideal companions.

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2

Choosing

Buying chilli seeds can be irresistible, with so many colourful varieties and different flavours
There are hundreds of varieties of chillies too choose from, offering fruits of various colours, shapes and sizes, ranging from mild to unbearably hot. Chilli heat is measured in Scoville Heat Units (SHU), with milder varieties such as ‘Anaheim’ rated at 500–2,500 SHU, ‘Jalapeno’ at 2,500–8,000 SHU, ‘Scotch Bonnet’ at 100,000–350,00 SHU and ‘Carolina Reaper’, one of the world’s hottest chillies, at 2.2 million SHU! Heat is not just dependent on the variety though, it can also vary according to the growing conditions and stage of ripeness.

Chilli plants vary in size from as little as 20cm (8in) tall and wide (ideal for a windowsill) up to 60cm (2ft) or more, depending on the variety, so select to suit your growing space. Also look for varieties with an RHS Award of Garden Merit (AGM), which shows they performed particularly well in our trials – check out our list of AGM fruit and veg and our Recommended Varieties below. You’ll also see lots of colourful chillies growing in the veg plots at the RHS gardens over the summer months, so do visit to compare varieties and pick up growing tips. 

What and where to buy

Chilli seeds are widely available in garden centres and from online seed suppliers. There are also many specialist chilli seed retailers, who offer the widest choice of varieties.

Many of these suppliers also sell young plants in spring and early summer. These are handy if you don’t have time to sow seeds or don’t have a suitably warm, bright place indoors to raise good plants. Another option is to buy grafted plants, which are more vigorous so should produce larger crops, and are especially useful if growing conditions are a little cool. They can be ordered from online suppliers for delivery from mid-April. Many retailers also sell chilli plants already in fruit over the summer months.

Recommended Varieties

Showing 3 out of 6 varieties
3

Sowing

Sow seeds indoors from late winter to mid-spring – chillies generally need a long growing season, and an early start will give you an earlier and longer harvest. Chilli seeds need warmth to germinate – around 21°C (70°F) – so it’s best to use a heated propagator, although a warm windowsill should be fine too. See our guide below for step-by-step sowing instructions.

As soon as your seedlings appear, take them out of the propagator and keep them at 16–18°C (60–64°F) in bright light, and water regularly. When they are 2–3cm (1in) tall, move each one into its own module or small pot of peat-free multi-purpose compost. Then, once roots begin to show through the drainage holes, move them into larger 13cm (5in) pots.

Carefully lever out individual seedlings...
...and replant singly in modules or small pots

4

Planting

Chillies grow well in pots, ideally in a greenhouse but also outdoors
Young chilli plants, either grown from seed or newly bought, must be kept indoors in the warmth, usually until at least late May. Then you can either plant them in their final container in a greenhouse or similar protected location, or get them ready for life outdoors.

Chilli plants grow and crop best in a greenhouse, polytunnel, conservatory or coldframe. Compact varieties can also be grown on a sunny indoor windowsill. In mild locations, you can consider planting them outside too, once night-time temperatures are reliably at least 12°C (54°F), usually by late May or early June. Take care to harden them off for two to three weeks, to acclimatise them to outdoor conditions. Chillies need your warmest, sunniest spot to produce a good crop outdoors, ideally on a sunny patio or by a south-facing wall. Plant them in their new location at the same level they were previously growing in their pot, and add canes to support taller varieties.

To grow in containers, plant one in a 22cm (9in) pot filled with peat-free multi-purpose compost, or plant three in a standard growing bag. See our guides below for more tips.

To grow in the ground, choose a spot with well-drained, fertile, moisture-retentive soil that is ideally slightly acidic. To achieve this, dig in moderate amounts of well-rotted manure, at a rate of 5.4kg (10lb) per square metre/yard, but avoid using fresh manure or large quantities, as this can lead to lush, leafy growth at the expense of fruit. Next, warm the soil with cloches for a couple of weeks before planting. Space chilli plants 38–45cm (15–18in) apart, depending on the variety. Dwarf varieties can be spaced 30cm (1ft) apart. Then cover young plants with cloches to provide wind protection, preferably until the end of June.

5

Plant Care

Temperature and humidity

Chilli plants can usually cope with a minimum night temperature of 12°C (54°F), but will grow better if kept above 15°C (59°F). However, temperatures over 30°C (86°F) can reduce fruiting, so in hot spells keep the greenhouse well ventilated and put up shading.

Chillies prefer a humid atmosphere, so raise the air’s moisture content in warm weather by ‘damping down’ the greenhouse daily – pour a full watering can over the floor, then leave it to evaporate.

Watering

Water little and often to keep the soil or potting compost evenly moist, avoiding waterlogging and drought. Flower buds may fall off if plants get too dry. Also add mulch to help hold moisture in the soil. Plants in containers can dry out very quickly in summer, so check the compost regularly – see our video guide to watering efficiently.

Feeding

Feed chilli plants with a high potassium liquid fertiliser weekly, as soon as flowering starts.

Overwintering

Chilli plants can be overwintered in a heated location, rather than started afresh each year. This will give you a head start on your chilli production the following year. Plants should be pruned back to a manageable size, then kept in a warm, bright place, such as an indoor windowsill or conservatory, and watered sparingly. See our video guide below for full details.

6

Pruning and Training

To encourage side-shoots, which should carry more fruit, pinch out the shoot tips once plants reach 30cm (1ft) tall.

Large plants and those in growing bags may need support. Use several canes per plant, and take care when tying in the stems, as they can be brittle.

7

Harvesting

When growing in a greenhouse, you can usually keep picking chillies well into autumn
Chillies are generally ready for harvesting from mid-summer into autumn if grown in a greenhouse. Fruiting outdoors should start by August. Towards the end of the season, bring plants indoors if possible, to help the remaining fruits develop. You can also use grow lights to extend the cropping season indoors – see our video guide below for tips.

To maximise your crop, pick your chillies when still green, either to use at that stage or to ripen further in the kitchen. If left on the plant to ripen, they will change colour and may develop a hotter flavour, but will deter the production of new flowers, leading to a reduction in the overall harvest of 25 per cent or more. However, you may prefer to let the fruits mature on the plant to get a richer, hotter flavour and for their decorative appeal, despite a smaller harvest.


 
8

Storing

Harvested chillies can be easily dried or frozen, so you can enjoy your crop through the winter too.

9

Problems

Storing
Guide Start
Section 9 of 9

Chillies usually crop best in a greenhouse – when grown outdoors, fruiting may be reduced, especially in cooler summers. Several sap-sucking insects can cause problems, particularly in a greenhouse, so check plants regularly – see below for details. Young chilli plants also need protection from slugs and snails.

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