Growing Hot Chillies and Peppers in Australia

Pick your heat level, start early, feed for fruiting, and grow superhots in pots anywhere in the country

Chillies are one of the most rewarding crops you can grow. A single healthy plant can carry hundreds of fruit, the plants are pretty enough for a pot by the back door, and homegrown chillies have a depth of flavour and heat that bought ones rarely match. The catch is that chillies, and superhots especially, are slow. They need a long, warm season, so the gardeners who succeed are the ones who start early.

This guide covers everything from picking a heat level that suits you, through starting seed early indoors, feeding for fruit rather than leaves, ripening for maximum heat, growing the fierce superhots in pots in cooler areas, and handling hot chillies safely.

Scoville Heat Units (SHU) measure capsaicin, the compound that makes chillies hot. A capsicum sits at zero, a jalapeno is a few thousand, and the superhots run past one million. For the full ladder see our chilli heat scale guide.

A long, warm season

Chillies are tropical perennials grown as annuals in most of Australia. They love heat and hate cold, and they fruit best with a long run of warm weather. In the tropics and subtropics they grow almost year-round and can live for several seasons. In cool-temperate areas the season is short, so you make the most of it by starting early and choosing faster varieties.

The hotter the chilli, the longer it takes. A jalapeno fruits in a single warm summer. A Carolina Reaper can need five months or more of warmth from transplant to ripe fruit, which is why an early start matters so much.

Start early indoors

Because chillies are slow, sow seed indoors in late winter, about 8 to 10 weeks before your last frost, earlier than you would sow tomatoes. Superhots are the slowest of all and benefit from the earliest possible start.

Chilli seed needs real warmth to germinate, ideally a soil temperature of 25 to 30 degrees Celsius. A heat mat is close to essential for an even strike, especially for habanero and superhot types, which can take 3 to 6 weeks to come up even when warm. Be patient and keep the mix warm and just moist.

Planting out and growing on

Plant chillies out only once all frost has passed and the soil is warm, in the warmest, sunniest, most sheltered spot you have. They need full sun, free-draining soil and warmth at the roots. In cool areas a wall that holds the day's heat, or a spot against the house, gives them the extra warmth that lifts the crop.

Space plants about 40 to 50 cm apart, water consistently, and mulch to keep the roots cool and the moisture even. A short stake helps heavily laden plants stay upright once they are carrying fruit.

Feeding for fruit, not leaves

Feed chillies the way you feed tomatoes. While the plant is young and building leaves, a light balanced feed is fine. Once flowering and fruiting begin, switch to a potassium-rich feed, such as a tomato or flowering-plant fertiliser. Potassium drives flowering, fruit set and ripening.

The classic mistake is too much nitrogen, which gives a big lush green bush and very few chillies. If your plant is all leaves and no fruit, ease off the nitrogen and switch to potassium.

Why late stress can raise heat

Variety sets most of a chilli's heat, but how you grow it nudges the result. Capsaicin tends to build when the plant is under a degree of stress, particularly later in the season. A controlled, gentle stress can lift heat:

• Ease back slightly on water as the fruit matures. A plant that is kept a touch drier late in the season often produces hotter fruit than one watered to luxury.
• Plenty of sun and warmth builds heat. The hottest, brightest position gives the hottest fruit.
• Let the fruit fully ripen. Heat keeps building as the chilli colours up and matures on the plant.

Ripening green to red

Most chillies start green and ripen through to red, orange, yellow or brown depending on the variety. You can pick and eat them green, but ripening changes everything. A fully ripe chilli is sweeter, more complex in flavour, and noticeably hotter than the same chilli picked green. A red jalapeno, for example, is hotter and sweeter than a green one.

Leave fruit on the plant to colour up if you want maximum heat and flavour. If frost threatens before they ripen, pick mature green fruit and ripen it indoors on a windowsill, or pull the whole plant and hang it somewhere warm.

Growing superhots in pots in cool areas

You can grow even a Carolina Reaper in Hobart or Melbourne, as long as you grow it in a pot. A container lets you beat a short, cool season:

• Start under cover. Sow very early and raise the plant indoors or in a glasshouse while it is still cold outside.
• Move it to the heat. Put the pot in the hottest, most sheltered, sunniest spot once it warms up, and wheel it into the sun as it tracks across the yard.
• Protect it. Bring the pot under cover if a cold snap threatens at either end of the season.
• Overwinter it. Chillies are perennials. Cut the plant back, keep it dryish and frost-free over winter, and it surges away the next spring for a much earlier, bigger crop.

Use at least a 30 to 40 cm pot, a good free-draining mix, and feed regularly, because potted plants run out of nutrients faster than ones in the ground.

Handling hot chillies safely

• Wear disposable gloves when picking, cutting or processing hot chillies.
• Keep your hands away from your face the whole time.
• Wash hands, knives and boards thoroughly with soapy water afterwards. Oil or full-fat milk cuts capsaicin better than water alone.
• If you are drying or grinding superhots, do it in a well-ventilated space, as the airborne dust will catch in your throat and eyes.
• If chilli burns your skin, dairy (milk or yoghurt) soothes it far better than water.

Got a glut of hot fruit? Turn it into something you can keep all year. See our how to make hot sauce guide.

Frequently Asked Questions

See also: The Chilli Heat Scale, How to Make Hot Sauce and Chilli in the Plant Library