How to Grow Chillies

To add some heat and colour to your dishes, growing your own chilli seeds allows you to taste varieties that aren’t found in supermarkets. As well as adding some spice to your cooking, chilli plants also look great within a growing space, producing vibrant blooms and pods. The key thing to know when growing chilli peppers is that heat produces heat, as growing chillies in warm environments, such as greenhouses or cold frames, will intensify their heat.

To find out how to grow chillies, we’ve put together this comprehensive guide to help you healthily grow these vegetable seeds. Below, you can find out our best advice on each stage of growing to help you produce chillies that are packed with intense flavour.

Choosing

You should research which chilli peppers would best meet your preferences before growing, as they can vary quite significantly in heat. Chilli pepper heat is measured using the Scoville scale, which measures capsaicinoids (the component of chilli peppers that gives them their heat) in Scoville units, or SHU.

For example, Chilli Jalapeno would be a good choice for those looking for chilli peppers with a comparatively milder flavour at a SHU of 2,500–8,000. Alternatively, those seeking extreme heat should choose the Chilli Carolina Reaper, previously regarded as the hottest chilli pepper in the world with a SHU of 2.2 million, until the cultivation of Pepper X in 2023 by the same breeder, Ed Currie.

Choosing chilli seeds or plants according to your spatial needs is also important, as chilli plants can grow several metres high. However, this doesn’t mean that those with smaller growing spaces can’t grow chillies, as there are several varieties of dwarf chillies that grow excellently in pots.

Chillies should be grown in a sunny spot with well-drained soil. Though they can be grown in the ground, the UK’s cooler climate means that they grow best in a greenhouse with plenty of heat to bring out their spiciness. Keeping your chilli plants warm is important for their heat intensity, which is why the hottest chilli peppers are grown in the hottest parts of the world, such as India, Mexico, and the USA.

For growing in the UK, chillies need to be grown early in January to ensure they ripen properly over a longer growing season, ready for the summertime. This should be done indoors under a heated garden propagator, such as our Extra Large High Dome Electric Propagator, at a temperature between 20 to 25°C. Otherwise, seeds can be sown indoors from March onwards on a warm, south-facing windowsill if you are growing without a propagator.

Once seedlings begin to develop, you should pot your plants according to the space they need, keeping them on a warm windowsill. After propagation, they should be moved into small pots or modules, then moved on to larger 13cm (5in) pots when roots can be seen near the drainage holes. You should take extra care when moving them to avoid accidental damage to their roots.

Around May, they should be large enough to handle. At this point, you should carefully transplant them into 25cm (10in) containers or grow bags. They should be grown inside a greenhouse or cold frame to keep them at the right temperature and protect against late and early frosts. Alternatively, they can be planted out to a sunny, sheltered spot once night temperatures reach at least 10°C, spacing your plants 50cm (20in) apart.

Watering

You should water chilli plants little and often to ensure the soil remains moist, especially when conditions are warmer in summer. However, you shouldn’t allow the soil to get soaking wet, as this can lead to diseases such as root rot.

Mulching

Adding a layer of mulch, such as garden compost, well-rotted manure, leaves or straw, can help to keep soil moist and prevent it from drying out. This can be quite useful in summer when soil is more likely to become dry.

Feeding

Chilli plants should be fed each week with a high-potassium liquid fertiliser once they first set fruit. This provides them with essential nutrients for growth.

Training

Some larger varieties of plants may need support. So, you should tie your plants to 60cm (24in) canes if you have one of these, ensuring that you’re gentle with the brittle stems.

Pinching Out Tips

You should pinch out the growing tips when your plants reach about 20cm tall, as this will lead to better plant and crop growth.

Producing Hotter Chillies

An unusual recommendation for a growing guide, but you can experiment with putting your plants under stress to achieve hotter chillies. This can be done by watering your plants less often, and avoiding feeding or snipping off stems or fruit when fruit begins to set. Using these techniques could result in a reduced yield or no yield, though doing so can cause the chillies to reach hotter flavours than usual.

Chillies will be ready for harvest in late summer or August. For those looking for a milder flavour, they can be picked when green. However, picking them when they mature and turn red will provide a more intense heat. They can be picked by cutting them off your plant with a pair of secateurs.

If the weather begins to cool before they’re fully ripe, you can continue to grow them until they mature indoors on a warm, sunny windowsill.

Picking peppers while they’re still young will encourage the growth of more crops. So, it can be worthwhile to either dry or freeze these and then use them when needed.

Chilli plants can be treated as perennials and overwintered, as they will crop again next season. Just keep in mind to prune them back to a manageable size during winter. Water them sparingly, and keep them in a warm, sunny area.

Chillis are usually problem-free when growing when cared for properly. However, there are one or two common issues that can arise to bear in mind below: 

• Pests - Chilli plants can be susceptible to being eaten by snails and slugs when young, and sap-sucking insects such as aphids and whiteflies can also pose problems. Therefore, you can protect your plants with slug and snail control products and pest and disease control products. However, using garden netting works best as a preventative, rather than reactive, measure.
• Diseases - Some diseases, such as root rot and blossom-end rot, can affect chilli plants. However, these are generally prevented by ensuring chilli plants are not watered too little or too ofte