Got a message from a mate up in the Blue Mountains last week asking if his chilli plants were going to make it through winter. Looked at his photos. Yeah, they’ll be fine if he does the right things now. The thing is, “the right things” depend a lot on where you are. Sydney winter is different to Hobart winter, which is different to Brisbane winter, which barely counts as winter.

A practical guide for getting chillies through the cooler months in Australia, broken down by climate zone.

What’s actually happening to the plants

When daytime temperatures drop below 18°C consistently, most chilli species slow their growth dramatically. Below 12°C they essentially stop. Below 8°C, they’re stressed. Below 5°C, leaf damage starts. Below 0°C, you’re losing the plant unless you intervene.

The plants aren’t dying when they slow down — they’re hibernating, more or less. The leaves drop off, the stems go a bit yellow, the plant looks miserable. None of that means the plant has given up. It means the plant is running in low-power mode and waiting for spring.

The key knowledge: chillies are perennial in their native range. The annual treatment most of us give them — plant in spring, harvest in autumn, pull out in winter — is a habit we picked up from tomato culture. It’s not what the plant wants.

Climate zone playbook

Sydney, Brisbane, Perth, Adelaide (coastal subtropical and warm temperate). Most chillies will overwinter outside if you give them basic protection. Move pots out of direct south-facing wind, mulch the base, reduce watering to almost nothing. Prune back any wet or rotting growth as it appears. The plant will look terrible by July. It’ll be fine by October.

Melbourne, Canberra (cool temperate, with frost risk). Outdoor overwintering is workable for the more robust varieties (most Capsicum annuum) but riskier for the hotter species (Capsicum chinense — habaneros, scotch bonnets, the supers). For these, bring pots into a sheltered position — a covered veranda, a sunny window inside, a greenhouse if you’ve got one. Aim for the plant to spend the coldest two months at minimum 8°C.

Hobart, Ballarat, Bendigo (cold temperate). Indoor overwintering for almost everything. The frost risk is real and the daytime warmth in winter isn’t enough to keep plants in active growth. Bring pots inside, accept that the plants will be lanky and unhappy until spring, and plan to harden them off carefully in September-October.

Tropical north (Cairns, Darwin, Townsville). Not really applicable. Chilli plants in tropical climates run year-round, with the practical limitation being the wet season and the associated disease pressure. The ‘winter’ work in tropical zones is more about disease management and structural pruning than cold protection.

What to do this fortnight

For most Australian growers, mid-to-late May is the right time to do the work that sets the plant up for winter survival.

Prune lightly. Take off any dead or dying leaves, remove any small immature fruit that won’t ripen, and tidy up the plant’s shape. Don’t go aggressive — significant pruning should wait until late winter when the plant is fully dormant and the wound heal-over isn’t being interrupted by new growth.

Mulch the root zone. A 5-8cm mulch layer around the base of the plant, kept clear of the actual stem. The mulch insulates the root system from temperature swings and provides slow-release nutrition for spring restart.

Reduce watering meaningfully. The plants need much less water in winter than summer. Overwatering in winter is one of the most common causes of overwintering plant loss — the roots rot in cold wet soil and the plant doesn’t recover. Aim for the soil to dry out between waterings.

Stop fertilising. Active fertilisation through winter encourages soft growth that’s vulnerable to cold damage and disease. The plants don’t need it. Resume in late August or early September.

Watch for pests. Cool, sheltered conditions are ideal for several pest species that don’t bother chillies in summer — particularly mealybugs and certain mite species. Check the undersides of leaves regularly. Treat early if you see infestation.

Indoor overwintering specifics

For growers moving plants inside for winter, a few practical specifics.

Light is the binding constraint. Indoor light levels in winter are dramatically lower than outdoor light, even on a south-facing window. The plants will get leggy and weak. Either accept this and plan to prune hard in spring, or invest in supplemental grow lighting. Modern LED grow lights are cheap to run and produce good results.

Temperature stability matters more than warmth. Plants are better off at a stable 12°C than at a fluctuating 8-18°C range. Avoid placing pots near doors that open frequently, heaters that cycle on and off, or windows that get cold at night.

Humidity is usually the indoor problem. Australian houses in winter often run very dry, especially with heaters running. Chilli plants prefer 50-70% relative humidity. A small humidifier or pebble tray helps; clustering plants together raises local humidity.

Watch for aphids and mealybugs. Indoor plants in winter are particularly vulnerable. Inspect regularly. Treat with horticultural soap or neem at the first sign rather than waiting for a major infestation.

What to plan for spring

The work you do now sets up what spring looks like. A few specific things to be thinking about as winter approaches.

Cuttings. If you’ve got varieties you want to propagate, take cuttings before the plant slows down completely. Mid-May is a workable cutoff for getting cuttings to root before winter dormancy. The cuttings can overwinter as small rooted plants and provide insurance against losing the parent plant.

Seed saving. If you’ve harvested fruit recently and saved seed, store it properly through winter — dry, cool, dark. The viability holds up well over multiple years if storage is done right. The seed you save now extends your variety options for next season.

Soil refresh. The pots that contained chilli plants this year will be depleted in nutrients. Late winter and early spring is the time to refresh the potting mix, top up with fresh compost, and have the soil ready for spring planting.

Greenhouse and shelter improvements. If overwintering taught you anything about gaps in your setup — drafts, water pooling, light deficiencies — winter is when you can address them before next season.

The plants will get through. They’ve evolved to handle worse than an Australian winter throws at them. The grower’s job in May is to make the conditions as favourable as possible for the dormant phase and to set up for a strong spring restart. Do that work now, and the spring you get out of these plants will reward the effort.