How to Grow Chillies in Australia

Chilli (Capsicum annuum and four related species) is a frost-tender nightshade, family Solanaceae, grown for pods from gently warm to ferociously hot. Plants crop for months, and for years in frost-free gardens, but the most common stumble comes first: seed sown into cold mix. Sweet capsicum, the same genus bred without heat, has its own guide: How to Grow Capsicums.

Three mistakes that matter

1. Sowing into a cold mix. Chilli seed then germinates slowly and unevenly, and seed sitting in wet mix can rot. Keep trays warm and just moist (see When to plant).
2. Planting out before the weather settles. Frost kills most chillies, and they stop growing below 10°C, so early transplants simply stall. Wait until frost has passed and the nights stay mild.
3. Feeding and watering for leaves. Too much nitrogen and constantly wet soil grow a lush bush with few chillies. Feed moderately, switch to potassium at flowering (see Care by growth stage), and let pots dry a little between drinks.

When to plant

Keep the mix at 27°C to 30°C for chilli seed, which germinates very slowly in cooler soil. Raise it on a seedling heat mat or in a warm room. Sow about eight weeks before your planting-out date, which comes once frost has passed and the soil holds at least 18°C. One sowing a year usually does, because plants crop for months.

In the tropics, rain and high humidity raise disease risk. Sow habaneros and superhots at the start of any window, since some take 130 days or more to mature.

Site, soil and setup

Give chillies the hottest, brightest spot you have. Cold soil, wind and waterlogging hold them back far more than heat does.

Container growing

Chillies have shallow roots and crop well in pots, which warm the roots and can bring an earlier harvest. For a balcony, 'Firecracker', 'Explosive Ember' and 'Cupala Ornamental' stay compact.

• Mix: premium potting mix with fertiliser added; pot seedlings up one size at a time.
• Water: let the mix dry a little, then soak it; a light pot is due. Stand a dried-out pot in a bucket of water for about 10 minutes.
• Feed: fish and seaweed blend at 25 mL per 9 L fortnightly, then liquid potash per label fortnightly from the first flowers.
• Position: at least six hours of sun, sheltered from wind.

Sowing Seeds

Start chillies in punnets or cell trays under cover, then plant them out once the weather has warmed. Due to quarantine restrictions and our shipping policy, we cannot send chilli seeds to Western Australia.

Chilli types

Heat, seed speed and season length follow the species, and most chillies grown in Australia are C. annuum.

Starting under cover

• Sow 5 mm deep in seed-raising mix and keep it just moist.
• Most types show in 7 to 21 days; habanero and superhot seed can take up to 4 weeks.
• Grow them on in bright light at about 21°C by day and 16°C at night, so they do not turn leggy.

Planting out

• Harden off (accustom seedlings to sun and wind) over about a week.
• Plant when seedlings carry buds but no open flowers, at the depth they grew in the pot.
• Space plants 40 to 50 cm apart, in rows about 1 m apart.
• Choose a still, mild day, since seedlings set out in hot, windy weather often die.
• Water in with seaweed solution at half strength, and mulch, keeping it clear of the stems.

Pollination

Chilli flowers are self-fertile, so a single plant sets fruit without a partner. Insects still carry pollen, and varieties of the same species cross readily, which matters only for saved seed (see Tips).

Fruit sets best when nights stay between 18°C and 27°C. Long spells below 15°C or above 32°C weaken the pollen and leave small or misshapen pods.

• On still days, or under cover, tap flowering stems around midday to shake pollen loose.
• Or touch a small, soft paintbrush inside each open flower in turn.
• Under a plastic tunnel, open the covers on sunny days above 29°C, since trapped heat drops blossom.

Care by growth stage

Even moisture, and potassium from flowering on, carry a chilli through its season. Weeks count from planting out.

If you prefer a conventional feed, rake a controlled release all-purpose granular (NPK 12-3-8 to 14-5-10) into the bed at planting. Until the first flowers, water on an all-purpose soluble (NPK 23-4-18 to 27-5-9) fortnightly at label strength. Then switch to a fruiting and flowering soluble (NPK 15-4-26 to 15-5-20), also fortnightly.

Pruning and Training

Chillies need training more than pruning: laden branches are brittle and snap, and plants kept over winter need a hard cut.

• Stakes: one sturdy stake per plant, or several canes for tall habaneros, ajis and rocoto, pushed in at planting before roots spread.
• Ties: soft and loose, with more added as fruiting branches grow heavy.
• Tip pinching: optional; nipping the tip at about 30 cm trades a later start for more, smaller pods.
• Winter: in frosty areas, cut plants back by about half and water sparingly. Move pots under the eaves, or where frosts are hard, into a sunroom or glasshouse.
• Spring: in late winter, top up or repot overwintered plants, and cut sprawling rocoto back with loppers.

Companion planting

Good partners feed the predators of chilli pests; poor ones share those pests.

Grows well with

• Sweet alyssum, whose flowers feed hoverflies; their larvae eat aphids and thrips.
• Coriander and dill left to flower, which draw ladybirds and parasitic wasps.
• Nasturtium, a trap crop that pulls aphids away from nearby plants.
• Basil, which wants the same warm, well-watered bed.

Keep apart

• Tomato, which shares Queensland fruit fly, tomato grub and root-knot nematode (Meloidogyne species).
• Potato, which shares green peach aphid and the potato virus Y it carries.
• Eggplant, a host of broad mite and root-knot nematode.
• Strawberries, a favourite host of two-spotted mite.

Harvesting Fruit

Chillies can be picked at any stage, green or coloured, and most grow hotter and richer as they ripen. The first pods are usually ready 9 to 14 weeks after planting out.

• Cut each chilli with scissors or secateurs, leaving 2 to 3 cm of stalk; pulling tears branches.
• Wear gloves for hot types, and keep your hands away from your eyes.
• Keep superhot pods and plants away from children and pets.
• Pick often, since pods left to ripen early in the season hold back new flowers.
• Before frost, pick every pod, green or not, or move potted plants under cover to finish ripening.

Fresh chillies keep two to three weeks at 7°C to 13°C in humid air, away from tomatoes. For longer keeping, freeze them whole, or string cayenne and bird's eye types up to dry; fleshy rocoto dries poorly on a string.

Use them fresh in salsas and sauces, dried and crushed into flakes, or whole on the barbecue.

Common problems

Blossom end rot. A sunken, watery brown patch at the tip of the pod, caused when uneven watering, waterlogging or heavy feeding cuts the calcium supply. Lime belongs in bed preparation, not as a cure. Read more

Sunscald. Pale, papery blisters form on pods left without leaf cover in strong sun, and can let rot in. Use light shadecloth through fierce heat.

Damping off. Seedlings collapse at soil level soon after they emerge, most often in wet, cold, crowded trays; see Three mistakes. Read more

Pods hotter or milder than expected. Heat varies with variety and growing conditions. A crop of 'Padron' mixes mild pods with the odd hot one.

Tomato spotted wilt. This virus, spread by thrips, marks leaves and pods with rings and blotches and cannot be cured: pull and bin infected plants. Read more

Bacterial spot. Small, sunken leaf spots merge until leaves yellow and fall, and rain splash spreads the bacteria in wet, windy weather.

Pests and diseases

Use only sprays labelled for the pest on chillies, and keep to the withholding period before picking.

Queensland fruit fly (Bactrocera tryoni). Females sting ripening pods and the maggots tunnel through the flesh, which soon rots. It reaches Canberra late in the season. Freeze stung and fallen fruit in a sealed bag for two days before binning it. In Western Australia, where it is not established, report maggots in chillies to DPIRD. Read more

Tomato grub (Helicoverpa armigera). Its caterpillars, up to 40 mm long, chew holes into pods, which then rot. Also called cotton bollworm or corn earworm, it is managed like its look-alike, native budworm (Helicoverpa punctigera). Check the top third of the plant for eggs, and spray Bt (Bacillus thuringiensis) on caterpillars under 7 mm.

Green peach aphid (Myzus persicae). Colonies cluster on soft shoot tips, and the greater harm is the viruses they spread, such as potato virus Y. Hose them off or spray insecticidal soap. Read more

Broad mite (Polyphagotarsonemus latus). Too small to see without a strong lens, it leaves new growth bronzed, stiff and rolled under, and chilli shoots often die back. Pull and bin the first plants to show symptoms, before the mites spread.

Two-spotted mite (Tetranychus urticae). Pale stippling spreads out from the main veins as the mites feed under the leaves, and numbers climb fast in hot, dry weather. Spray wettable sulphur or horticultural oil underneath, but not on hot days. Read more

Root-knot nematode (Meloidogyne species). These microscopic worm-like animals knot the roots with lumps of 1 to 10 mm, and plants stunt, yellow and wilt. Dig in organic matter, and give potted chillies fresh mix at each replanting. Read more

Prevention first

• Where fruit fly is active, bag pods from first set or net plants in fine mesh pinned to the ground and clear of every pod.
• Check shoot tips and leaf undersides weekly with a hand lens for mites and aphids.
• Water the soil, not the leaves, and handle plants only when they are dry.
• Pull sowthistle and other weeds, which shelter aphids, thrips and the viruses they spread.

Tips

1. Save seed from fully ripe pods of healthy, open-pollinated plants grown away from other chillies of the same species; F1 hybrids do not come true. Wear gloves to scrape out the seed, which can burn.
2. Where summers are too hot for capsicum, try chillies: they tolerate extreme summer heat better.
3. If a chilli burns too much, reach for milk or yoghurt rather than water, which tends to spread the heat.