When to sow chillies

Chillies need a long, warm season, far longer than a Central European or UK summer gives them outdoors. That's why they are among the first seeds you sow each year: indoors, in February or early March. Many varieties need well over 100 days from sowing to the first ripe pod, and the earlier start means a longer picking season.

The slowest species, habaneros and other Capsicum chinense, the fruity baccatum types and rocoto, can go in as early as January. In the dark weeks that only works with a grow light, otherwise the seedlings stretch towards the window and flop. Quick, compact annuum chillies such as jalapeño or cayenne still crop well from a sowing in mid-March.

There is no sense in sowing chillies straight outdoors here. The soil doesn't get warm enough until early summer, which leaves too little time for fruit to ripen.

Fill a small tray or pots with seed compost, sow the seeds 0.2–0.4 in deep and a couple of centimetres apart, and water gently with a spray so they don't wash out. Label every variety: seedlings of different chillies look identical.

Warmth is what makes or breaks chilli germination. Keep the compost at 72–82°F, ideally around 77°F, in a heated propagator or on a warm spot, not on a cold windowsill. At that warmth most seeds show in one to three weeks. Habaneros and other chinense types are often slower, and cool compost can stretch it to a month, so don't give up too soon.

Once the seedlings are up, take them out of the propagator and grow them a little cooler, around 64–72°F, in the brightest place you have. Warmth with poor light gives tall, weak plants. After about three weeks, when the first true leaves appear, prick them out into their own small pots, and pot them on again as soon as roots show at the drainage holes.

From April, put them outside on warm, still days to harden off, and bring them in at night. Plant them out or into the greenhouse from mid- to late May in Germany, Austria and Switzerland, after the Ice Saints, and in late May or early June in the UK. The rule of thumb: nights should stay above 54°F. Chillies planted into cold soil simply sit still.

Give chillies the warmest, sunniest place you have. A greenhouse or polytunnel gives the most reliable crop, which is why commercial growers in Central Europe grow them only under cover. Outdoors, a spot against a south-facing wall, a sunny balcony or a patio works well, especially for compact annuum varieties.

In the bed, space them 16–20 in apart in rows 20–24 in apart; compact varieties manage with 12 in. A 120 × 80 cm raised bed takes two staggered rows of three, six plants, or four of the big baccatum and rocoto types. In pots, a 9 in pot is enough for small varieties, while large plants want 15–20 litres.

Chillies are heavy feeders. Work compost or horn shavings into the soil before planting, then give a high-potassium liquid feed, such as tomato feed, once a week from the first flowers. Keep the soil evenly moist but never waterlogged; pots may need water every day in hot spells.

Flowers that drop off without setting fruit are usually a temperature problem. Chillies set best with nights around 59°F and days below 86°F. Cold nights, a very hot greenhouse or dry soil all make the plant shed its flowers. Ventilate on sunny days, water regularly, and give tall plants a cane before they are heavy with fruit.

In a greenhouse the first chillies are ready from July; outdoors expect them from August. Picking goes on until the first cold nights in October. Cut the fruit off with scissors or a knife rather than pulling, as the brittle branches snap easily.

You can pick chillies green, and regular picking keeps the plant flowering. Left to ripen to their final colour, red, orange, yellow or purple depending on the variety, they taste fuller and are usually hotter. Heat also depends on the variety and on how the plant was grown.

The heat sits mainly in the pale ribs inside the pod and in the seeds around them. Wear gloves when you cut hot chillies and keep your hands away from your eyes: capsaicin clings to skin and water alone won't wash it off.

Thin-walled chillies dry well threaded on a string or hung in bunches somewhere airy and shaded, which takes a few weeks. Fleshy ones are better dried in a very low oven or a dehydrator, frozen or pickled. Frozen chillies go soft but keep their flavour and heat for months.

Capsicum annuum is the easy one. It includes jalapeño, cayenne, Thai chillies and most compact pot varieties, as well as all sweet peppers. It germinates and ripens fastest, so it is the best choice for a first year and for growing outdoors.

Capsicum chinense brings the fierce heat: habanero, Scotch bonnet and the record-holders such as Bhut Jolokia and Carolina Reaper. These are slow to germinate, need more warmth and a long season, and ripen reliably only with an early start and ideally a greenhouse.

Capsicum baccatum, the Peruvian aji types such as Aji Limon (Lemon Drop) or Bishop's Crown, are fruity rather than brutal, grow into big plants and need a very long season. Capsicum frutescens, best known as Tabasco, bears small, upright and always very hot pods.

Capsicum pubescens, the rocoto, is the odd one out: hairy leaves, purple flowers and black seeds. It comes from the Andean highlands and copes with cooler days better than the others, but it is not frost-hardy either and needs the longest season of all. Overwintering it pays off.

Chillies are perennials in their home climate, grown as annuals here only because they can't take frost. A plant in a pot can come indoors for the winter, and next year it starts with a full root system, flowering and fruiting weeks earlier than a new seedling. That matters most for the slow chinense, baccatum and rocoto types.

Bring the pots in before nights drop below about 54–57°F. Pick any remaining fruit, remove damaged or diseased growth, and check closely for aphids and spider mites, which multiply fast in dry indoor air. Many growers cut the plant back to its main branches to make it easier to keep.

Keep it as bright as possible at 50–59°F; in a dark spot it will fail. Water only enough that the compost never dries out completely, and don't feed. In February, move it somewhere warmer, repot into fresh compost and start feeding again once new leaves appear.

Aphids, whitefly and red spider mite are the usual pests, especially under glass and indoors. Check the undersides of leaves regularly; spider mite loves hot, dry air, so damping down the greenhouse floor helps. Grey mould can strike in cool, damp spells, so ventilate well.

A dark, sunken patch at the tip of the fruit is blossom end rot. It isn't a lack of calcium in the soil but uneven watering, which stops calcium reaching the fruit. Keep the compost evenly moist, especially in pots.

Chillies belong to the nightshade family with tomatoes, potatoes, aubergines and sweet peppers. They suffer less from soil-borne problems than potatoes and tomatoes, but in a bed it's still wise not to plant them straight after another nightshade, and to leave about three years between them where you can. In pots with fresh compost every year, rotation doesn't matter.

Mixed-planting tables often put chillies next to basil, marigolds or lettuce and keep them away from fennel, peas and beans. We found no studies behind these pairings for chillies; they are gardening tradition. Low crops like lettuce or basil between the plants do no harm and use the space well.