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A green, a red and a yellow bell pepper lying side by side on a pale surface

Bell pepper

Capsicum annuum Grossum Group
Care level: Moderate

The bell pepper, or sweet pepper, is the mild, blocky-fruited form of the same species as the chilli. It is an upright, bushy plant with dark green, lance-shaped leaves and small white flowers, each of which sets a hollow, thick-walled fruit. A recessive gene means the fruits contain none of the compound that makes chillies hot. It is a tropical plant grown as an annual, and it needs more warmth and a longer season than a tomato: in a cool climate that means a greenhouse, a polytunnel or the warmest, most sheltered spot you have.

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Varieties and related species
Capsicum annuum 'California Wonder'Capsicum annuum 'Redskin'Capsicum annuum 'Corno di Toro Rosso'

Light

Full sun and as much warmth as possible.

Water

Keep the compost evenly moist. Never let it dry out, and never leave the pot standing in water.

Humidity

Not a factor outdoors. Under glass, very dry air causes flower drop and encourages red spider mite; damp down the floor on hot days.

Soil

Fertile, moist but well-drained, slightly acid soil, or a large pot or growing bag of good compost.

Temperature

Frost tender and slow below about 15°C. Grow it under glass or in the warmest, most sheltered place outdoors.

Size

0.5-1m tall and 30-60cm wide.

Growth speed

Medium

Toxic to pets

Toxic to cats and dogs if eaten.

Mostly mild mouth and stomach irritation.

If your pet has eaten some, contact your vet.

Source: RHS

Did you know?

Green peppers are unripe peppers. Every bell pepper starts green and turns red, yellow, orange or purple as it ripens, becoming sweeter on the way. Ripening takes two to three more weeks, and a plant left to colour its fruit sets fewer of them, so pick some green and let the rest ripen.

Spring

Pot on the seedlings and harden plants off. Plant out or move to final pots after the last frost.

Summer

Flowering and fruiting. Water evenly, feed weekly, support the stems and pick the first fruits green.

Autumn

Ripen the last fruits under cover and harvest everything before the first frost.

Winter

Sow in late winter in warmth.

Planting

Plant after the last frost, once nights stay above about 10°C, 40-50cm apart, or one plant to a pot of at least 10 litres. Add a balanced fertiliser at planting.

Fertilising

Feed again when the first flowers appear, then weekly with a high-potash liquid fertiliser once fruits are setting.

Pruning

Pinch out the growing tip when the plant is about 20cm tall if it has not branched by itself. Keep picking to encourage more fruit.

Support

Tie the main stem to a cane and support branches that carry several fruits.

Propagation

By seed sown indoors in warmth in late winter.

Common problems

Flowers fall without setting fruit

Most likely cause: Dry compost, cold nights, great heat or very dry air.
What to do: Water evenly, ventilate and keep nights above 12°C if you can.

Dark, sunken patch at the base of the fruit

Most likely cause: Blossom end rot from irregular watering.
What to do: Water regularly and remove affected fruits.

Fruits stay green

Most likely cause: Not enough time or warmth.
What to do: Sow earlier next year and ripen late fruits indoors.

Pale, papery patch on the side of the fruit

Most likely cause: Sun scald on fruits suddenly exposed to strong sun.
What to do: Leave enough foliage to shade them and shade the glass in heatwaves.

Small plants with few fruits

Most likely cause: Cold, a small pot or a late start.
What to do: Use a larger pot, feed weekly and grow under cover.

Branches snap

Most likely cause: The weight of the fruit.
What to do: Stake and tie in before the fruits swell.

Pests & Diseases

Aphids

Signs: Clusters of small insects on shoot tips and under young leaves, with curled, sticky growth.
Treatment: Rinse or squash them early.

Red spider mite

Signs: Fine pale speckling on the leaves and thin webbing in hot, dry air under glass.
Treatment: Raise the humidity, rinse the foliage and ventilate. Check the undersides of the leaves and the crevices where the leaf stem meets the main stalk.

Whitefly

Signs: Clouds of tiny white insects that fly up when the plant is touched, with sticky leaves.
Treatment: Hang yellow sticky traps and rinse the undersides of the leaves.

Grey mould

Signs: Fluffy grey mould on flowers, fruits and stems in cool, damp, still air.
Treatment: Remove affected parts, water in the morning and ventilate.

When should I sow bell peppers?

Indoors in late winter to early spring, at about 20°C or a little more. They need a long season, so do not sow late. Pot the seedlings on and keep them warm and in good light until planting out.

Why are the flowers dropping without setting fruit?

Dry roots, cold nights, extreme heat and very dry air all make peppers shed their flowers. Keep the watering even, ventilate in hot weather and give the plants a gentle shake when in flower under glass to help pollination.

Why are my peppers staying green?

They need more time and warmth. Colour comes two to three weeks after the fruit reaches full size, and it stalls when nights turn cold. At the end of the season, cut the plant and hang it somewhere warm, or ripen the fruits on a windowsill.

Why do the fruits have a dark, sunken patch at the bottom?

Blossom end rot, caused by irregular watering, which stops calcium reaching the developing fruit. Water evenly, never let pots dry out and remove the affected fruits.

Do the plants need support?

Yes, once they carry fruit. Tie the main stem to a cane and prop heavily laden branches, which otherwise snap.

Can I grow bell peppers outdoors?

In warm regions, yes. In a cool climate they crop reliably only under glass or plastic; outside, choose the base of a sunny wall, plant out late and use an early, small-fruited variety.

Are bell peppers hot?

No. They lack the compound that gives chillies their heat. The seeds can cross with chillies grown nearby, though, so do not save seed if you want it to stay mild.

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