How to Grow Chillies Indoors: Seed to Harvest and Overwintering

Chillies are a good crop to grow indoors: they need more warmth and light than a British spring provides, they fruit happily in a pot, and a plant kept over winter crops earlier the next year. This guide runs from sowing to harvest and on to overwintering. The heated propagators, pellets and propagation lights to start them are in our propagation section.

When to sow chillies, and how

Chillies need a long season, so UK gardeners commonly sow indoors from January to March, the hottest types first. Our sowing seeds indoors guide says to sow them before your tomatoes, in a heated propagator.

Sow into Jiffy 7 Peat Pellets, swollen first as that guide describes, in the propagator it names for chillies: the Garland XL High Dome Heated Propagator warms the compost on a thermostat, and its page says to open the twin vents to let damp air out. Gardeners commonly look for a steady 20-25°C; a ThermoPro TP358 under the lid shows what the propagator holds, with the 24-hour high and low. Seedlings commonly take one to three weeks to show, longer for the hottest types.

Light: the difference between leggy and stocky

A February windowsill is too dim, so seedlings stretch; a propagation light is the usual answer. The Gorilla Propagation LED 12W (balanced blue, for roots and compact early growth; the power lead is sold separately) and the Maxibright LED T5 Propagation Lights (2-tube or 4-tube) both run cool, so they sit close over the tray, their pages say. Run either for 18 hours a day on a Time-R Digital Timer, the 18/6 schedule in our growers' glossary; hanging heights are in our grow lights for indoor plants and seedlings guide.

Chillies are not short-day plants: they flower once big enough, whatever the day length, so the hours need not change from seedling to harvest.

Pots and soil

Pot on when roots show through the pellet. Square to Round Pots come in 1, 2, 3 and 5.5 litres: the square bases pack tight while plants are small, and the page says a couple of sizes take a plant from seedling to its final pot. Fill them with a light mix: Biobizz Light Mix (its page recommends 1 or 2 litre pots for young plants, fed once established) or Plagron Lightmix Soil (lightly fertilised; it needs a soil nutrient, its page says).

For the final pot, our general practice is the 5.5 litre Square to Round for a compact variety and the 9l Air Pots for a bigger one. Air-Pots dry out faster than standard pots, the page warns; plastic stays wet longer, as our pots guide says. On a windowsill or in a greenhouse, tie a tall variety to one of our 150 cm Bamboo Canes.

Feeding chillies

Our Biobizz feed chart runs Bio Grow alongside Bio Bloom through eight weeks of flowering, then a week of water only (the flush: see our growers' glossary). A chilli fruits for months, so our advice is to start each feed low, hold the mid-flowering doses while it crops, and leave the water-only week until the last picking. The PK 13/14 page says it works with any nutrient range and crop.

Flower drop is commonly down to heat, cold, dry air or too much nitrogen. A dark, sunken patch on a fruit's end is blossom end rot, a calcium shortage in the fruit: calcium moves with the water the plant drinks, so check the watering before adding cal-mag, as our cal-mag guide says. Coco or hydroponics? See which nutrients for soil, coco and hydro.

A grow tent for chillies

A tent with an LED grow light lets you grow chillies in any season. Indoors there are no pollinating insects, so tap the open flowers regularly to set fruit, and keep a clip fan moving the air.

Every tent needs extraction, both Budbox pages say: see our fan and carbon filter guide. These short tents suit compact varieties: our what size grow tent guide shows how much height the pot and light take, and covers bigger tents. The watts are from our LED wattage by tent size guide (the tent pages give HID ratings); the Switch Blade suits small to medium spaces, its page says, and the Daylight 200W PRO covers 0.6 x 0.6 to 0.8 x 0.8 m and dims to 25% for young plants.

Harvest

Pick chillies as they colour up, cutting them off with the Chikamasa PST-8 Pruning Shears (their page lists harvesting among their jobs); picking keeps the plant producing. To dry them, pick them fully coloured and see our how to dry chillies and herbs guide.

How to overwinter a chilli plant

Chillies are perennials. Our general practice:

1. Bring it in before the first frost and cut it back. Pick the last fruit, then cut the plant back by about half to a framework of main stems.
2. Clear the aphids. They often hit chillies kept indoors over winter, our aphids guide says. Hang Sticky Fly Traps to spot them early and spray SB Plant Invigorator at 10 ml per litre: its page says it kills aphid and is safe on edible crops.
3. Keep it frost-free and, as a rule of thumb, above about 10°C. In a cold room or greenhouse, a tube heater on a thermostat can keep it there: our heaters guide compares the Hylite Tube Heaters and Gorilla Tube Heaters and shows how to control them safely.
4. Give it light. In a dark corner it drops its leaves, so stand it on a bright windowsill or under a light on the timer: our grow lights guide names the lights for chillies kept over winter.
5. Water sparingly, only when the pot feels light, and stop feeding until spring.
6. In spring, repot into fresh light mix, restart Bio Grow at 2 ml per litre and move it back under the grow light or to the brightest window.

Quick answers

How long do chillies take to grow?

Around four to six months from sowing to the first ripe fruit, as a rule of thumb, the hottest types slowest.

Why are there greenfly on my chilli plant?

Aphids breed all year indoors with nothing to eat them. Squash or wash off small colonies, hang Sticky Fly Traps and spray SB Plant Invigorator.

Do chillies need a grow light indoors?

For seedlings sown from January to March, usually yes: a windowsill is too dim and they stretch, and a 12 W propagation LED suits them. A sunny windowsill or greenhouse ripens the fruit in summer without one; to grow them in any season, use a small tent with a 150 to 200 W full-spectrum LED.

More Growers' Guides

• Sowing seeds indoors
• How to dry chillies and herbs
• Aphids, greenfly and blackfly

Not sure what you need? Call the shop on 0117 971 3000 or pop in to the Bristol store and we'll help you pick.