How to Grow Chillies: Seed to Harvest in a Short Season

Chilli quick facts

On this page

• Chilli quick facts
• Which chilli species should you grow?
• How hot will it be? The Scoville scale explained
• When should you sow chilli seeds?
• Do chillies need grow lights?
• Potting on, pot sizes and pinching out
• How to grow chillies in a greenhouse, a bed or a container
• Zone chart: sowing, planting and harvest for USDA zones 3–6
• Watering, feeding and pollination
• Blossom end rot, aphids and other problems under glass
• Harvesting, ripening, drying and storing
• Can you overwinter chilli plants?
• Common mistakes
• Frequently asked questions

Which chilli species should you grow?

This is the section most growers skip, and it decides your season. "Chilli" is not one plant but five cultivated species in the genus Capsicum, and they need very different amounts of time. The species, not the variety, tells you which month to sow.

Capsicum annuum

The common and forgiving one: jalapeño, serrano, cayenne, padrón, Anaheim and ordinary sweet peppers. Plants stay compact at 40–80 cm (16–32 in) with plain white flowers. Seed germinates in seven to twelve days, the plant sets fruit even in mediocre light, and 55–90 days after transplanting you have something to pick.

Capsicum chinense

Habanero, scotch bonnet, bhut jolokia, Carolina Reaper. Despite the name the species comes from the Amazon, not China. The fruits are wrinkled and lantern-shaped, the aroma floral and fruity, and the heat on a different scale entirely.

The price is time. Seed germinates in two to four weeks, and the plant needs 90–120 days from transplant before fruit ripens. That means sowing in January and running lights until April. Sow a habanero in March and you get a handsome green plant in October and no harvest.

Capsicum baccatum

The aji types, such as Aji Amarillo and Aji Blanco Cristal, plus bell-shaped varieties like Jamaican Bell. The giveaway is the flower: yellow-green or tan spots on white petals. Plants get large and sprawling, often over a metre (3 ft). Sow in January or February and grow under cover.

Capsicum frutescens

Tabasco and most seed sold as bird's eye. Small upright fruits in dense clusters, often hundreds per plant. The bushy habit makes these the easiest species to overwinter.

Capsicum pubescens

Rocoto and manzano. The odd one out: purple flowers, hairy leaves and, uniquely in the genus, black seed. From the Andean highlands, it is the only species that shrugs off cool weather down to about 5 °C (41 °F). It is also the hardest — seed germinates erratically and first-year plants often give nothing.

Turning species into a sowing date

The species is nearly always printed on the packet in italics under the variety name. If nothing is stated, it is almost certainly annuum.

How hot will it be? The Scoville scale explained

Scoville Heat Units, SHU, measure pungency. The scale was devised in 1912 by the pharmacist Wilbur Scoville and relied on a taste panel: how much sugar solution it took to dilute the burn until nobody could detect it. Since the 1980s capsaicinoid content has been measured by high-performance liquid chromatography. A sweet pepper sits at zero, pure capsaicin at 16 million.

The ranges are wide, and that is not sloppiness. The same variety varies with growing conditions: drought stress and strong sun push heat up, generous water and nitrogen bring it down. Padrón is famous for it — roughly one fruit in ten is hot, the rest mild. And the heat is not in the seeds: capsaicin forms in the white internal ribs, the placenta, that the seeds attach to. Scrape the ribs out and most of the burn goes with them.

For a first season, pick two varieties rather than eight: one mild annuum you will eat fresh, and one hot type you dry and grind. In a short season, Hungarian Hot Wax, Serrano and Cayenne are the safest bets — they ripen early and cope with an unheated greenhouse.

When should you sow chilli seeds?

January for a chinense, February for an annuum. Work backwards from planting out: the plant needs ten to twelve weeks indoors before it moves outside, plus the species' own development time. In zones 3 and 4 that pushes annuum sowing into early March, because your last frost is three weeks later than zone 6.

General pepper advice says eight to ten weeks before the last frost, which works for sweet peppers and jalapeños. It does not work for superhots: a Carolina Reaper started that late in zone 4 will still be flowering when the first autumn frost arrives.

Sowing step by step

1. Fill a propagator or small pots with moist seed compost. Chilli seed wants a fine, low-nutrient mix — rich potting soil scorches new roots.
2. Space seed 2–3 cm (1 in) apart and cover with 0.5–1 cm (1/4–1/2 in) of compost. Chillies germinate better in darkness, so cover properly and firm gently.
3. Water from below or mist with tepid water. Cold tap water drops the compost temperature for hours.
4. Put the tray on a heat mat or somewhere reliably 25–28 °C (77–82 °F). Below 20 °C (68 °F) germination is patchy or fails, and a chinense can sit six weeks doing nothing.
5. Keep the lid on until seedlings appear, venting five minutes daily so mould cannot take hold. Germination takes 7–21 days.
6. Remove the lid and move the tray under lights the moment the seed leaves show. Drop to 18–22 °C (64–72 °F). Light now matters more than heat: a seedling left warm and dim stretches into a pale thread in three days.
7. Water sparingly. Seedlings die of wet compost far more often than of drought.

Soaking and saved seed

Stubborn chinense and pubescens seed germinates more evenly if you soak it in tepid water for 8–12 hours, or pre-sprout it between damp kitchen paper on a heat mat. Move sprouted seed into compost straight away — the root snaps easily once it is a few millimetres long.

Seed from a supermarket chilli often grows, but you have no idea what variety you will get, and seed from dried chillies rarely germinates. Chillies also cross readily, so saved seed only comes true if the plant was isolated. The technique for raising nightshade seedlings indoors is covered in the guide to when to sow tomato seeds.

Do chillies need grow lights?

Yes, if you sow before March at a northern latitude. In January the day is seven to nine hours long in zone 5 and shorter further north, and mostly overcast. A south-facing window does not deliver enough light to build thick leaves and short internodes. Without a lamp you get seedlings 20 cm (8 in) tall, pale and so thin they fold over.

• Hours: 14–16 hours a day to mid-March, then 12 hours, and from late April a bright window will do.
• Distance: 15–25 cm (6–10 in) between an LED grow light and the tops of the plants. Too close and the leaves bleach; too far and the plants stretch.
• Darkness: switch it off at night. Plants need the dark period to build sturdy cell walls.
• Type: a 20–40 W full-spectrum LED covers a tray of ten to fifteen plants. Household bulbs and under-cabinet strips deliver far less usable light than they appear to.

Seedlings raised in still indoor air stay spindly. Run a small fan on its lowest setting for two hours a day, or brush your hand across the tops daily. The mechanical stress thickens the stem, and the difference is obvious by April.

No lamp? Sow in March in the brightest window you have and choose an early annuum. Hungarian Hot Wax, Serrano, jalapeño and cayenne still ripen from a March sowing under glass in zones 5 and 6.

Potting on, pot sizes and pinching out

Chillies root fast and stall above ground the moment the pot is too small. Step them up in three or four moves through spring rather than planting straight into the final container — a small plant in a big pot sits in cold, airless compost.

1. First move: at two or three true leaves beyond the seed leaves, usually three to four weeks after germination. Into 7–8 cm (3 in) pots of potting compost.
2. Second move: at 15–20 cm (6–8 in) tall, once roots show at the drainage holes. Into 1 litre (1 quart).
3. Third move: into 3–5 litres (0.8–1.3 US gal) in April.
4. Final pot: 5–10 litres (1.3–2.6 US gal) for compact varieties, 10–15 litres (2.6–4 US gal) for large baccatum and chinense, at planting-out time.

Chillies tolerate being buried deeper at each move. Unlike cucumbers, the stem throws new roots from the buried section just as tomatoes do, so a leggy seedling is rescued by sinking it to the seed leaves next time.

Should you pinch out chilli plants?

Pinching out the growing tip forces the plant to branch: a bushier plant with more but smaller fruits, at the cost of delaying the first pick by a couple of weeks. Pinch annuum and baccatum at the third to fifth leaf pair, roughly 15–20 cm (6–8 in) tall. Leave chinense and frutescens alone — they branch on their own. In zone 3 or 4 the season is too short to repay the delay.

Do always pinch off the first flowers that appear while the plant is still indoors in April. A plant that sets fruit at 25 cm (10 in) effectively stops growing, and you end up with five large pods instead of fifty. The logic matches pruning tomato suckers: steer the plant's energy early, with your fingers rather than secateurs.

How to grow chillies in a greenhouse, a bed or a container

Harden off first

Chillies raised under lights scorch in direct sun — leaves go white and papery in a morning. Put plants in outdoor shade for two hours on day one, then build up time and light over seven to ten days, taking them in at night until nights clear 10 °C (50 °F).

Under glass

A greenhouse or polytunnel is the right place for chillies in zones 3–5. Plant when night temperatures inside stay above 12 °C (54 °F), which in most of zone 5 means the last week of May. Space plants 40–50 cm (16–20 in) apart, or keep them in pots so they can move back indoors in September.

Chillies want drier air than cucumbers and take more heat than tomatoes, but above 32 °C (90 °F) fruit set stops because the pollen goes sterile. Ventilate in the morning, shade the roof in a heatwave, and close up in the late afternoon. Chillies and tomatoes share a house happily, while a cucumber's demand for humidity makes it an awkward neighbour — see the guides to how to grow tomatoes and how to grow cucumbers.

In a garden bed

Outdoor chillies work in zone 6 with an early annuum and are a gamble in zone 4 or colder. Plant at the earliest two weeks after your last frost date, once soil at 10 cm (4 in) depth has reached 16 °C (60 °F) and nights sit above 12 °C (54 °F). A night at 5 °C (41 °F) will not kill the plant, but it stalls it for a fortnight you cannot spare.

Choose the warmest spot you have, ideally against a south-facing wall that stores heat. Black plastic mulch lifts soil temperature several degrees, and low hoops with fleece through June make a real difference in zones 4 and 5.

In containers

Containers are the best setup in a cold climate, and the most underrated. The advantage is mobility: out on the deck in June, back under cover for a cold week in July, indoors in October so the last fruits colour up.

Allow at least 5 litres (1.3 US gal) per compact plant and 10–15 litres (2.6–4 US gal) for large types. A pot against a south wall in zone 5 often out-yields the same variety in open ground in zone 6, because the wall radiates heat back overnight. Otherwise the rules match growing tomatoes in pots.

Zone chart: sowing, planting and harvest for USDA zones 3–6

Chillies are grown as annuals, so hardiness zones say nothing about winter survival. They are still a useful shorthand for how long and warm your season is. Treat the dates as guides and adjust to your own frost records.

Two things stand out. Sowing dates shift by only about four weeks between zone 6 and zone 3, while the harvest window shrinks from thirteen weeks to four. Chillies are therefore the crop where a greenhouse or a movable pot buys the most — an unheated greenhouse is worth roughly two zones.

Second, in zones 3 and 4 late fruit is normal rather than a failure. Bring the whole pot indoors in September and stand it somewhere bright: the fruit ripens on the plant well into November, and the plant is heading for overwintering anyway.

Watering, feeding and pollination

Watering

Compared with cucumbers and tomatoes, chillies are close to a desert plant. They want even moisture but not wet soil, and suffer more from too much water than too little. Let the top 2 cm (3/4 in) dry out between waterings — lift the pot, and if it feels light it is time.

A plant in a 10-litre pot on a sunny July day drinks 0.5–1 litre (0.1–0.25 US gal). Water in the morning, at the roots, with tepid water, and mulch with compost or coir to halve evaporation. Even moisture is what keeps blossom end rot away.

Drooping leaves in midday sun do not always mean drought — chillies wilt as self-protection and recover in the evening. Check the soil first, because a plant watered every time it wilts is waterlogged within a week.

Feeding

• Sowing to first potting on: no feed. Seed compost is enough and young roots scorch.
• From first potting on: a quarter-strength liquid feed at every second watering.
• April to flowering: full strength once a week. Nitrogen builds leaf and stem, which is what you want now.
• From the first flower: switch to a high-potassium feed, the kind used for tomatoes. Potassium builds fruit, nitrogen builds leaves, and an overfed plant flowers late and drops those flowers.
• From mid-September: stop feeding.

Older lower leaves yellowing in July is usually nitrogen shortage. Yellow patches between the veins with the veins still green is magnesium deficiency, common in containers, corrected with Epsom salts at a tablespoon per 10 litres (2.6 US gal).

Pollination

Chillies are self-fertile: every flower carries both anthers and stigma, and pollen falls onto the stigma when the flower is shaken. Outdoors, wind and insects handle it. Indoors and in a closed greenhouse, shake each plant gently every day while it flowers, or twirl a soft brush inside each bloom around midday when the pollen is dry. Flowers that yellow and drop without setting usually mean temperatures above 32 °C (90 °F), uneven watering, too much nitrogen, or simply a plant already carrying all it can support.

Harvesting, ripening, drying and storing

Almost every chilli can be picked green, but the full flavour and heat only arrive at ripe colour — red, orange, yellow, brown or purple depending on variety. It is ripe when the colour is even across the pod and the skin has gone slightly glossy.

Cut with scissors and leave a centimetre (1/2 in) of stalk; pulling the fruit tears bark from the branch. Continued picking pushes the plant to set new flowers, so pick often. A jalapeño in a 10-litre pot typically gives 20–40 fruits, a cayenne 40–60, and a tabasco or bird's eye easily more than a hundred small ones. Habaneros give fewer but heavier pods, often 15–30 per plant.

Drying and freezing

• Air drying: for thin-walled types like cayenne and bird's eye. Thread the fruits on a string and hang them somewhere warm and airy indoors. Two to four weeks.
• Dehydrator: 50–60 °C (120–140 °F) for 8–12 hours. Fastest and safest for thick-walled types that otherwise mould.
• Oven: lowest setting, door propped open, 6–10 hours. The fruit should turn brittle, not browned.
• Grinding: grind dried pods in a spice mill with the window open and gloves on. Capsaicin dust is genuinely unpleasant.
• Freezing: jalapeños and other thick-walled types dry badly. Freeze them whole in a bag — chillies keep heat and flavour without blanching.

Fresh chillies keep two to three weeks in the salad drawer, better in paper than plastic. Dried chillies in an airtight jar hold their heat for a year.

Can you overwinter chilli plants?

Yes, and it is the best shortcut in chilli growing. Capsicum species are short-lived woody perennials, grown as annuals only because they freeze. An overwintered plant starts the year with an established root system, flowers several weeks earlier and often yields twice as much in year two. A chinense carried through winter fruits in July instead of September — in zone 4, the difference between a crop and none.

1. Bring it in early. Move the plant indoors when nights head towards 8–10 °C (46–50 °F), before the first frost.
2. Strip the fruit. Pick everything, including unripe pods, which finish ripening indoors.
3. Prune hard. Cut back to a framework of main stem and three to five short side branches, 15–25 cm (6–10 in) tall. Chillies take heavy pruning well.
4. Check for pests. Turn over every leaf, rinse the plant in tepid water and treat any aphids before it comes inside — an infestation in a heated room in November explodes.
5. Refresh the roots if you like. Trim the outer roots and repot into a slightly smaller pot of fresh compost.
6. Pick a strategy: cool dormancy or warm active growth, below.
7. Restart in February. Raise to 18–22 °C (64–72 °F), switch the lamp on, give a weak feed and cut out dead wood. New shoots appear within two to three weeks.

Cool dormancy, 8–15 °C (46–59 °F)

The simplest and safest option. An unheated spare room, a frost-free porch or a garage with a window all work. The plant sheds most of its leaves, which is normal. Water about half a litre (1 pint) every three to six weeks — the compost should be nearly dry. No feed, no lamp, aphid check monthly.

Warm active growth, 18–22 °C (64–72 °F)

Here the plant keeps growing at room temperature under 10–12 hours of grow light a day, and you can pick through winter. The downsides are a higher risk of aphids and red spider mite, more watering and feeding, and a lamp running all season.

The commonest reason overwintering fails is overwatering: a leafless plant at 10 °C (50 °F) uses almost no water, and cold wet compost brings root rot within weeks. Second is aphids that came indoors with the plant, third is a completely dark cellar — chillies need daylight even while resting.

Common mistakes

• Sowing too late. A habanero sown in March will not ripen in zones 3–6. Check the species on the packet.
• Sowing in January without a lamp. Midwinter daylight is not enough, and you get long, pale seedlings that never catch up. No lamp means sowing in March.
• Germinating too cool. Below 20 °C (68 °F) seed comes up patchily or not at all. A heat mat is not optional for chinense.
• Planting out too early. One night at 5 °C (41 °F) stalls a plant for two weeks. Wait until nights sit reliably above 12 °C (54 °F).
• Too much water. Chillies suffer more from wet compost than from dry. Do not water just because the leaves droop at midday.
• Too much nitrogen. Gives a big green plant that flowers late and drops the flowers. Switch to high-potassium feed at the first bloom.
• Letting the first flowers set. A small plant that fruits in April stops growing. Pinch them off until it is planted out.
• Giving up in September. Bring the pot indoors. The fruit finishes ripening there, and an overwintered plant makes next year far easier.

Frequently asked questions

When should you start chilli seeds indoors?
It depends on the species. Capsicum chinense such as habanero and scotch bonnet goes in during January, because it needs 90–120 days from transplant to ripe fruit. Baccatum and frutescens follow in January or February, and annuum varieties such as jalapeño and cayenne in February. Anything sown before March needs grow lights.

How long do chilli seeds take to germinate?
Seven to twenty-one days at 25–28 °C (77–82 °F), though chinense and pubescens can take four weeks. Below 20 °C (68 °F) germination is patchy or fails, so a heat mat makes the biggest difference. Soak stubborn seed in tepid water for 8–12 hours and cover with 0.5–1 cm (1/4–1/2 in) of compost, because chillies germinate better in the dark.

Do chilli plants need grow lights?
Yes if you sow before March. Midwinter daylight in zones 3–6 is not enough even on a south windowsill, and seedlings come up long, pale and thin. Run 14–16 hours a day from a full-spectrum LED 15–25 cm (6–10 in) above the plants, switched off overnight. Sow in March instead and an early annuum manages in a bright window.

Should you pinch out chilli plants?
Pinch annuum and baccatum at the third to fifth leaf pair, around 15–20 cm (6–8 in) tall. It gives a bushier plant with more shoot tips to flower on, but delays the first harvest by a couple of weeks. Chinense and frutescens branch on their own, and in zones 3 and 4 the season is too short to bother.

Why are my chilli flowers dropping without setting fruit?
Most often temperatures above 32 °C (90 °F), which makes the pollen sterile. Other causes are uneven watering, excess nitrogen and a lack of pollination indoors. Ventilate in the morning, shade the roof in a heatwave, switch to high-potassium feed at the first bloom, and shake the plant daily while it flowers.

What are the black sunken patches on my chillies?
Blossom end rot. It is caused by calcium failing to reach the tip of the fruit when the plant dries out, not by a calcium shortage in the soil. Water more evenly, mulch the surface and cut back on nitrogen. Remove affected fruits — they do not recover — but new pods come clean once watering is steady.

Can you overwinter chilli plants indoors?
Yes. Bring the plant in before nights drop below 8–10 °C (46–50 °F), strip the fruit and cut it back to 15–25 cm (6–10 in). Check for aphids, then keep it cool at 8–15 °C (46–59 °F) and water every three to six weeks with no feed. Restart in February with lights and 18–22 °C (64–72 °F). Year two often yields double.

Is the heat in chilli seeds?
No, that is a persistent myth. Capsaicin forms in the white internal ribs, the placenta, that the seeds attach to. The seeds taste hot only because they have been pressed against it. To take heat out of a dish, scrape out the white membrane — that removes far more burn than picking out the seeds.

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