How do I keep a chilli plant alive over winter?

Almost nobody realises that a chilli is a perennial shrub. In its native range it lives for years and gets bigger and more productive each season. Kept through a British winter, a second-year plant starts flowering weeks or months before a seed-sown one, which in a country this short of summer is a substantial advantage.

Step by step

1. Choose plants worth keeping.Keep the vigorous, healthy, productive ones. A weak or pest-ridden plant will not improve over winter and becomes a reservoir of problems for the greenhouse.
2. Pick every remaining fruit.Fruit left on the plant rots and drains it. Take everything, ripe or green, before you cut back.
3. Cut the plant back hard.Reduce it to a short framework — typically the main stem and the first fork or two, roughly 10–20cm of stem. It looks drastic and the plant regrows readily from it in spring.
4. Strip most of the remaining leaves.Fewer leaves means less water demand and far less habitat for red spider mite and whitefly through the winter.
5. Check the plant over thoroughly for pests.This is the step people skip and the reason most overwintering fails. Look under every remaining leaf for red spider mite, aphids and whitefly. Wash the plant down with water if in any doubt.
6. Repot into fresh compost if the pot is exhausted.Knock off some of the old compost, trim any circling roots, and repot into the same size pot with fresh compost. It gives the plant a clean start in spring.
7. Keep it frost-free, bright and cool.Around 10–15°C is ideal — a cool bright room, a heated greenhouse, a porch or a conservatory. It does not need to be warm; it needs to not freeze.
8. Water sparingly.Just enough to stop the compost drying out completely, perhaps every two or three weeks. Overwatering a leafless dormant plant in a cold room is the other main killer.
9. Do not feed until growth restarts.Leave it alone through the darkest months. Start a weak feed once new shoots appear in late winter or early spring.
10. Bring it back into growth in late winter.Increase light and warmth, water a little more, and start feeding as shoots appear. Pot on into fresh compost as it fills out, and it will be flowering well before this year's seedlings.

Tips

• The same approach works for sweet peppers and aubergines, though they are generally less successful than chillies.
• Perennial chilli species — rocotos and some C. chinense types — overwinter particularly well and reward the effort most.
• If the plant loses all its leaves, do not assume it has died. Scratch the stem: green underneath means it is alive and will shoot in spring.
• A plant in a cool room by a window usually does better than one in a warm living room, where it grows soft, drawn shoots that then collapse.
• Keep only one or two plants. Overwintering a whole collection means overwintering a whole pest population with it.

Common mistakes

• Bringing the plant in without checking for pests — Red spider mite in a warm dry house multiplies all winter with no natural enemies, and you carry the infestation back into the greenhouse in spring.
• Watering on a schedule through winter — A leafless plant in a cool room uses almost no water. Consistently damp compost rots the roots.
• Keeping it warm and dark — Warmth without light produces long weak etiolated shoots that collapse. Cool and bright is the combination.
• Leaving fruit on over winter — It rots, invites botrytis and drains the plant at exactly the point you want it dormant.

Keeping on top of it

• Check the undersides of remaining leaves for red spider mite and aphids (weekly)
• Check the compost and water only if it is drying right out (every 2–3 weeks)
• Remove any dead or mouldy material (monthly)

Questions people ask