How to grow chillies and the best varieties

Chillies are not only tasty but easy to grow. They do well in pots so thrive on a sunny patio, balcony or windowsill.

The Which? Gardening experts have grown-and-tasted 22 varieties of hot chillies and 16 varieties with attractive foliage and/or colourful fruits. 

They also share their tips for growing chilies from seed and how to grow chilli plants, including whether a bigger pot will give you more fruit or not.

If you don't want the spicy taste of chillies, read our guide on how to grow sweet peppers.

How to grow chillies: month by month

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Chilli heat levels explained

The spiciness of chillies is measured in Scoville Heat Units and is based on the concentration of capsaicinoids. These are the compounds that give chillies their hot flavour. For example, sweet peppers rate zero, jalapenos around 2,500-10,000, while habaneros are 100,000-350,000. 

The SHU give an indication of the hotness of a variety of chilli, but this can vary between fruits from the same and different plants depending on the ripeness of each frtui, and can also be affected by growing conditions. It's also important to note that we all have different perceptions of heat when we eat a chilli; what one person finds unbearable hot another might think is pleasantly warming. 

As a  rough guide, chillies can be divided into heat bands as follows: 

• Hot 25,000-50,000 SHUs 
• Very hot 50,000-200,000 SHUs 
• Extremely hot 200,000-750,000 SHUs 
• Super hot 750,000 SHUs and above 

When to sow chillies

You can either buy plants from the garden centre in spring or you can sow seeds from mid-February  to March in a heated propagator or on a warm windowsill. They need a minimum temperature of 18C to germinate. Starting off chillies early in the year will give them the opportunity to ripen their fruits over the summer.

Sow the seeds thinly in pots or trays of a Best Buy compost for sowing seeds. Cover with a light layer of fine compost or vermiculite. Keep the compost just moist; the seeds won't germinate if it dries out.

Carefully prick out the seedlings into individual pots using a Best Buy compost for raising young plants and pot on until they're in their final container, which needs to be 25-30cm wide. When potting on into the final container, use a Best Buy compost for containers and mix in a Best Buy controlled-release feed.

Best chilli varieties

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Full testing results for hot chillies

Full testing results for decorative chillies

How we test chillies

• We choose widely available varieties of chillies with either colourful fruits and attractive foliage or a reputation for flavour, including old favourites, newer varieties and some with a RHS Award of Garden Merit. 
• We then sowed the seeds in our greenhouse in early March. All the chillies were potted up into 9L pots in a Best Buy compost for containers to which we added some controlled-release fertiliser, and kept in a polytunnel. 
• They were fed weekly with tomato food as soon as they started flowering. 
• At the end of September, we assessed the plants for their ornamental value and how much ripe fruit they had produced. We also asked a small panel of tasters to assess the flavour and heat of the chillies, both dried and in a sauce.

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How to grow chilli pepper plants

Where to grow

Chillies will do best grown inside on a sunny windowsill or in a greenhouse if you have one. If you want to grow your chilli plants outside, wait until all risk of frost has passed in late May or early June  before moving to a spot outside in full sun. Chillies will be killed by frost if moved outdoors too early. 

Learn how to buy the best greenhouse

Choosing the right size pot

Chillies will respond to pot size; plants from the same sowing date will grow larger in a larger pot and conversely have their growth restricted in a smaller pot. 

We tried growing C. annuum ‘Kilian’ and C. chinense ‘Scotch Bonnet Red’ in a range of pot sizes. We grew ‘Kilian’ in 2L, 10L and 20L pots and ‘Scotch Bonnet Red’ in 5L, 10L, 20L and 40L pots to see what effect on plant size, chilli size and yield this would have. 

We found plant size and chilli size and weight were affected more than the number of chillies. The most marked differences were in the size and shape of the chillies; the ‘Kilian’ chillies from the 2L pot were much smaller and curled rather than straight, while the ‘Scotch Bonnet Red’ chillies from the smallest (5L) pot lost their distinctive bonnet shape and grew elongated and tapered instead. The ‘Scotch Bonnet Red’ chillies from the largest container kept their typical shape but were huge. 

Our verdict: For a smaller, more manageable plant, you can get away with a smaller pot, though the fruit shape may suffer. If you’re a chilli fiend, go large for impressive plants and weightier fruits.

Feeding and watering

Feed the plants weekly with a tomato fertiliser from when the first flowers appear and water whenever the compost is dry to the touch. This can be a twice a day in hot, dry weather.

Stake all but the shortest of varieties with a cane to support the stems under the weight of the developing fruit.

Discover the best garden irrigation systems

How and when to harvest chillies

Harvest in: September-November

Fruit should ripen by September or October, depending on the summer. If your chillies are not ripening outside, bring the whole plant inside to a sunny windowsill to encourage the process.  Mice will happily eat chillies, as will birds, so you may need to protect your plants if they show any signs of being attacked. 

If you want chillies the following year, try bringing the plant inside as soon as frost threatens. You can continue harvesting the ripe chillies during the winter and lightly cut back the plant to encourage fresh growth in February.

Try the best secateurs

Storing your chilli pepper harvest

Chillies are easy to dry or freeze fresh, so any surplus can be stored to be used later in the year. They can also be pickled in vinegar or added to oils for flavouring.

Common chilli problems

Aphids

These sap-sucking insects can weaken the plant and cause poor growth. Squash any you find or use a suitable organic insecticide.

Read more about how to get rid of aphids