Capsicum annum

Common name: Chilli pepper

Chillies are frost sensitive perennials that need relative warmth and good light, and because of this they are generally treated as annuals in the UK.

Ones geographical position in the UK will determine the best location to grow them.

That is, in warm sheltered areas in the south and west, they may be grown outdoors, but in cooler northern areas they are better grown under cover.

Potted specimens can be stood outside during the summer and brought indoors when the weather becomes cooler.

Plants can grow to a height of 900mm (36") depending upon variety, a characteristic that often determines if the plants are to be grown in pots or in the greenhouse border.

If grown in the greenhouse border, plant out 500-600mm (18"-24") apart.

Where greenhouses have a paved floor one can use the 'Ring Culture' method to grow their plants.

Similarly, low growing varieties can be grown in containers suited in size to the eventual height and spread of the variety.

The white flowers appear from June to August.

The fruits come in a range of size, colour and shapes, e.g. 12mm-200mm (½"-8") long, red, yellow or green in colour, and spherical, conical or twisted in shape.


Week 10: Sow seeds in pots of seed compost at a temperature of 21°C (70°F)

Germination usually take around 7-14 days although some varieties can take longer.

Week 14: When the seedlings are large enough to handle, prick them out individually into 75mm (3") pots of potting compost and pot on as necessary.

Start feeding with a balanced or high-nitrogen fertiliser until the plants are about 125mm (5") high.

Week 20: If the intention is to grow the plants outdoors, harden off plants in a cold frame before planting out.

Week 22: Plant out in a well-drained, fertile and moisture-retentive greenhouse border,500-600mm (18"-24") apart, 300-400mm (12”-16") for dwarf cultivars.

Alternatively, pot up into 150-250mm (6"-10") pots depending upon variety.

Tall growing cultivars and those with large fruit will require some means of support to hold them upright, the weight of fruit can make their branches break.


Germinated seedlings


Pricked out seedlings


Hardening off


Planted out

Week 23: Plant outdoors after the danger of frost has passed.

Indoors,maintain a minimum night temperature of 12°C (54°F), but better results are achieved above 15°C (59°F).

Avoid temperatures above 30°C (86°F) under glass, by providing maximum ventilation, and lightly shade the glass during the hottest months

Maintain high humidity in glasshouses by damping down twice a day in hot weather.

Water regularly but do not overwater, and give a balanced liquid fertiliser every 7-10 days.

Ensure water and feed are at air temperature! chillies react badly to cold compost.

Water little and often to keep soil evenly moist, avoiding both water-logging and drought.

Closer attention to watering and feeding is necessary with chillies in containers.

Ensure that they never go short of water and are adequately fed, a weekly balanced liquid feed is ideal.

Spray the leaves daily with water during the flowering period to assist fruit setting.

Pinch out growing tips* when plants reach 300mm (12”) tall to induce more fruiting branches.

* This task is optional; i.e. with some of the taller varieties this may not be required due the amount of fruit they produce naturally.

Encouraging plants to produce more fruit may give you the desired quantity at the expense of quality.

The reverse is generally true for low growing varieties.


Plants at various stages of growth


Fruit forming

Give a high-potassium liquid fertiliser at 7-10 day intervals after the fruits first appear and until they show a change in colour.

With indoor plants, insect pollination can sometimes be insufficient, to ensure good fruit set pollinate manually with a small artists paintbrush.

The fruits should be ready for picking in September / October depending upon variety.

Banana Sweet

Bulgarian Carrot



Red Cherry

Hot Wax

Winter Warmer


Potential problems

Chillies are relatively trouble free and are threatened by only a few pests and diseases, e.g.

Botrytis (grey mould) can appear in late autumn, but by then most of the fruit may well have been harvested.

Red spider mite, whitefy and thrips sometimes attack chillies, but aphids are the most likely pest to be encountered at home.

Fortunately, these are easy to keep in check,as light infestations can simply be rubbed off the plants, while sprays and predators efficiently deal with heavier invasions.

Aphids can transmit tobacco mosaic virus, which causes mottling of the leaves and debilitates plants.

Infected plants should be removed and destroyed.

Growing conditions and cultivation techniques can also affect the yield and quality of chillies.

High-temperature stress, for example, or lack of water, can cause flowers and young fruit to drop, while blossom end rot, a physiological disorder caused by calcium deficiency in the fruit can be caused by low pH, root damage and uneven watering.

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