Chilli Peppers

Chilli peppers are tender Capsicum plants grown for glossy fruits ranging from mild and sweet to intensely hot. Cultivars vary enormously in colour, shape, flavour and size. Compact plants may be only 20–30cm (8–12in) tall, while vigorous forms exceed 60cm (2ft), so even a sunny windowsill can support a useful crop.

Heat, humidity and abundant sunshine are essential. A greenhouse, polytunnel or sunny conservatory gives the most dependable yield, but plants can crop outdoors in a sheltered sun-baked position beside a south-facing wall or on a warm patio. They enjoy conditions similar to tomatoes and grow particularly well in containers.

Select cultivars for available space, desired fruit shape and manageable heat. Compact ornamental plants suit windowsills and containers, while taller cayenne types need more room and support. RHS Award of Garden Merit cultivars have performed reliably in trials.

Recommended varieties

‘Apache’ AGM

A compact F1 hybrid carrying abundant green fruits up to 7cm long that ripen bright red; hot at about 80,000 SHU.

Cultivar sourceAllotment Pro variety guide

‘Fuego’ AGM

A cayenne type with long tapering fruits, greater cold tolerance than many chillies and heat around 30,000–50,000 SHU.

Cultivar sourceAllotment Pro variety guide

‘Hot Thai’ AGM

A compact heavy-cropping plant producing up to 200 small bullet-shaped chillies at around 50,000–70,000 SHU.

Cultivar sourceAllotment Pro variety guide

‘Hungarian Hot Wax’ AGM

An early bushy cultivar with large conical fruits up to 10cm long, ripening yellow through orange to red with citrus notes and 5,000–15,000 SHU.

Cultivar sourceAllotment Pro variety guide

‘Loco’ AGM

A compact British-bred cultivar bearing masses of small oval fruits that turn green to purple, orange and finally fiery red; moderate heat around 20,000–30,000 SHU.

Cultivar sourceAllotment Pro variety guide

‘Prairie Fire’ AGM

A compact bushy ornamental crop with many small multicoloured upright fruits that become extremely hot as they ripen. ## 3 - Sowing Sow indoors from late winter to mid-spring. Chillies require a long season, and early seedlings have more time to flower and ripen fruit. Germinate at approximately 21°C (70°F) in a heated propagator or on a warm windowsill. Remove seedlings from the propagator as soon as they emerge and keep them in bright light at 16–18°C (60–64°F). Maintain evenly moist compost. When seedlings reach 2–3cm (1in), transplant each into an individual module or small pot of peat-free multi-purpose compost.

Cultivar sourceAllotment Pro variety guide

Sow indoors from late winter to mid-spring. Chillies require a long season, and early seedlings have more time to flower and ripen fruit. Germinate at approximately 21°C (70°F) in a heated propagator or on a warm windowsill.

Remove seedlings from the propagator as soon as they emerge and keep them in bright light at 16–18°C (60–64°F). Maintain evenly moist compost. When seedlings reach 2–3cm (1in), transplant each into an individual module or small pot of peat-free multi-purpose compost.

Keep young plants warm indoors until at least late May. Plant into final greenhouse containers or prepare them for outdoor conditions. Outdoor night temperatures must be reliably at least 12°C (54°F), usually in late May or early June. Harden plants off gradually for two to three weeks.

Use the warmest, sunniest sheltered position available. Plant at the same depth as before and provide canes for taller cultivars. Put one plant in a 22cm (9in) pot of peat-free multi-purpose compost, or three plants in a standard growing bag.

Chillies tolerate minimum night temperatures near 12°C (54°F) but grow better above 15°C (59°F). Temperatures over 30°C (86°F) can reduce fruit set, so ventilate and shade greenhouses during hot spells. Increase humidity by damping down greenhouse floors daily in warm weather.

Pinching growing tips is not essential. It can be done once plants reach about 30cm (1ft) to encourage bushier growth and more, smaller fruits, but may delay the first harvest. Some compact cultivars are pinched at around 20cm.

Support tall plants and those in growing bags with several canes. Tie stems loosely and handle carefully because branches become brittle when carrying fruit.

Greenhouse-grown chillies generally ripen from mid-summer into autumn, while outdoor fruiting should begin by August. Move container plants indoors near the end of the season if possible so remaining fruits can mature.

Pick green fruits regularly to maximise total yield, using them immediately or allowing them to colour indoors. Early fruits left to ripen fully on the plant develop richer and often hotter flavour, but slow new flower production and reduce the eventual crop. Later in the season, leave fruits to reach their mature colour.

Cool outdoor summers reduce fruiting, so protected growing gives the most reliable crop. Indoors and under glass, inspect leaves regularly for sap-sucking pests. Keep plants evenly watered, ventilate without chilling them and remove decaying material.

Common problems