Chilli Pepper

About

Sweet peppers and fiery chillies are the same species. Capsicum annuum covers bell peppers, jalapenos, cayenne, poblano and padron, and the difference between a bland salad pepper and something that hurts is a handful of genes controlling capsaicin production.

The critical decision in Britain is the sowing date. Chillies need a long season, often 100 to 150 days from planting out to a ripe red fruit, and a plant sown in April will still be carrying green fruit when the light goes in October. Sow in February.

Everything else follows from warmth. This is a plant of Central American lowlands, and a British summer barely satisfies it outdoors.

Appearance and character

A bushy branching plant, 45 to 90 cm depending on variety, with stems that turn woody at the base as the season goes on.

Leaves are oval, pointed and glossy mid-green, sometimes flushed purple in ornamental varieties.

Flowers are small, white or greenish-white, with five or six pointed lobes and purple anthers. They are self-fertile and set readily.

Fruit varies enormously. Blocky bells, long tapering cayennes, squat jalapenos, tiny upright bird’s eyes, all in green ripening to red, yellow, orange, purple, brown or near-black.

Every chilli is green before it ripens. Ripe fruit is sweeter, hotter and better-flavoured, which is the argument for sowing early enough to get there.

Where it is from

Central America and Mexico, where Capsicum annuum was domesticated at least six thousand years ago and where the wild ancestor, the tiny fiery chiltepin, still grows.

Capsaicin evolved as a defence against mammals, whose molars destroy seeds, while leaving birds unaffected because they lack the receptor it binds to. Birds swallow the fruit whole and distribute the seed intact.

Columbus took them to Europe in 1493 and they spread across Asia and Africa within a century, faster than almost any other New World crop. Indian, Thai, Sichuan and Hungarian cooking all rest on a plant that reached them after 1500.

The native climate is warm, bright and humid, with a long frost-free season. In Britain that means a greenhouse, a polytunnel or a sunny windowsill for anything other than the quickest varieties.

How it grows

Sow indoors from late January to early March, in a propagator at 21 to 25 deg C. Chilli seed germinates slowly and unevenly and hates cold compost.

Germination takes one to three weeks, and longer for the very hot varieties. Bottom heat makes the difference between a good and a poor strike rate.

Pot on as the plants grow, into 9 cm pots and then into their final 20 to 30 cm pot or growbag.

Grow on somewhere warm and bright. Cool nights early on stall the plants and set the season back.

Plant into their final position in May, keeping them under cover unless you have a sheltered sunny wall and a quick variety.

Pinch out the growing tip at about 20 cm to encourage branching, which gives more flowers and a sturdier plant.

Flowering starts in June, and fruit follows. Green fruit is edible; ripe fruit takes another three to six weeks and is worth waiting for.

Through the seasons

Late winter is sowing. Get seed in from late January to early March with bottom heat. This is the decision that determines the whole season.

Spring is potting on and growing under cover. Keep the plants warm and bright, and harden them off carefully before moving them out.

Summer is the crop. Feed weekly with high-potassium fertiliser once flowering starts, water evenly, ventilate the greenhouse, and watch for red spider mite.

Autumn ends outdoor growing. Pick everything before the first frost. Green fruit ripens indoors on a windowsill, and whole plants can be cut and hung upside down to finish.

Care difficulty

Moderate, and the difficulty is climate rather than technique.

Heat is the whole problem. Below about 12 deg C the plants sit and sulk, and below 15 deg C fruit sets badly. A greenhouse or polytunnel makes chillies easy and an exposed garden makes them frustrating.

Season length is the second issue. Ripening a habanero outdoors in Britain is unrealistic, and a jalapeno or cayenne is achievable.

Watering needs consistency. Swings cause blossom end rot and fruit drop.

Red spider mite is the standard greenhouse pest and thrives in exactly the hot dry conditions the plants want.

Watering

Keep the compost evenly moist through the growing season, watering thoroughly and letting the surface dry before the next.

Never leave the pot standing in water. Chillies rot at the root faster than tomatoes.

Reduce watering as the fruit ripens. Slightly drier conditions late in the season concentrate the flavour and, in hot varieties, the heat.

Water at the base rather than over the foliage.

Raise the humidity by damping down the greenhouse floor in hot weather, which also discourages red spider mite.

Overwintered plants need very little water, just enough to stop the compost drying out completely.

Warning signs, diseases and pests

Flowers dropping without setting fruit means the temperature is wrong. Below about 15 deg C or above 32 deg C the pollen fails. Ventilate a hot greenhouse and be patient in a cold spell.

Blossom end rot appears as a dark sunken leathery patch at the base of the fruit, caused by irregular watering rather than a soil deficiency. Water evenly.

Red spider mite produces fine pale stippling on the leaves and, in bad cases, webbing between the stems. It thrives in hot dry air. Raise the humidity and introduce the predatory mite Phytoseiulus persimilis under glass.

Aphids cluster on the soft growing tips and spread virus.

Whitefly rise in clouds when the plant is disturbed and coat it in sticky honeydew.

Grey mould rots ripening fruit in damp still conditions. Ventilate.

Leaves curling upward without discolouration is usually a heat response rather than a problem.

A plant that stayed small and pale all season was sown too late, kept too cold, or both.

Growing environment

Full sun, and as much as you can give. A greenhouse, polytunnel, conservatory or south-facing windowsill all work.

Minimum 15 deg C for good growth, and 20 to 30 deg C is the productive range.

Free-draining, moderately fertile compost. Use a good multipurpose compost with added grit, or a loam-based John Innes No. 2 for larger plants.

A final pot of 20 to 30 cm, or two plants to a growbag.

Support taller varieties with a cane once they carry fruit, since a laden branch snaps.

Choose the variety to fit the site. ‘Hungarian Hot Wax’, ‘Jalapeno’ and ‘Cayenne’ ripen readily in Britain. Habaneros and the superhots need a heated greenhouse and a very long season.

Feeding

Feed weekly with a high-potassium tomato fertiliser from the moment the first flowers open.

Before flowering, use a balanced feed sparingly. Too much nitrogen early gives a large leafy plant and little fruit.

Container plants depend entirely on liquid feed once the compost is exhausted, which happens by midsummer.

Magnesium deficiency, showing as yellowing between the veins on older leaves, is common on a heavy potassium regime. Epsom salts as a foliar spray corrects it.

Stop feeding in autumn as the plant winds down.

Troubleshooting

Flowers keep dropping. Temperature. Below 15 deg C or above 32 deg C the pollen fails. Ventilate in heat, and wait out a cold spell.

The fruit is still green in October. Sown too late. Pick it and ripen it on a windowsill, or hang the whole plant upside down indoors. Sow in February next year.

Dark sunken patch at the end of the fruit. Blossom end rot from uneven watering. Water consistently.

Fine pale speckling and webbing on the leaves. Red spider mite. Raise the humidity and damp down the floor.

The chillies are not hot enough. Heat rises with sun, with ripeness, and with slight water stress late in the season. It is also largely fixed by the variety.

How do I make them less hot in cooking? Remove the pale pith and the placenta the seeds attach to. That is where the capsaicin sits, rather than in the seeds.

I have chilli on my hands and water will not shift it. Capsaicin is oil-soluble. Use oil, milk or washing-up liquid. Wear gloves next time and keep your hands away from your eyes.

Can I keep the plant for next year? Yes. Cut it back by two thirds in autumn, keep it above 10 deg C somewhere bright, water sparingly, and start feeding again in March. An overwintered plant crops earlier and heavier.