Peppers

Sweet peppers (*Capsicum annuum*), including blocky bell peppers and long pointed forms, are tender, sun-loving plants grown for glossy, mild fruits. In the UK they crop most reliably in a greenhouse, polytunnel, conservatory or coldframe. Outdoor plants need a mild site, a long hot summer and cloche or fleece protection early and late in the season.

Seed must be started indoors in warmth. Plants usually reach about 60cm high and 30cm wide, so they fit well in pots and growing bags. Fruit begins green and may ripen red, yellow, orange or purple according to cultivar. Fully coloured peppers are sweeter, while harvesting green fruit encourages the plant to set and develop more.

Sweet peppers vary from wide rounded pimento and bell shapes to narrow tapering horns. Pointed peppers generally have thinner skins and a sweeter flavour. Large fruits need longer to mature, so compact cultivars with smaller peppers are safer outdoors or in containers where the growing season is short.

Recommended varieties

Sweet pepper ‘Topepo Rosso’ AGM

An Italian heirloom producing heavy yields of rounded, blood-red, pimento-type fruits 7–8cm wide. The very thick crisp flesh is sweet and well suited to stuffing.

Cultivar sourceAllotment Pro variety guide

Sweet pepper ‘Redskin’ AGM

A compact 45cm plant suited to containers, carrying medium-sized fruits from July.

Cultivar sourceAllotment Pro variety guide

Sweet pepper ‘Mohawk’ AGM

A dwarf patio cultivar about 50cm tall, producing bell-shaped fruits up to 10cm long.

Cultivar sourceAllotment Pro variety guide

Sweet pepper ‘Bianca’ AGM

A 60cm mid-season plant with large fruits that change from cream to yellow as they ripen.

Cultivar sourceAllotment Pro variety guide

Sweet pepper ‘Jolly Giallo’

Square-shaped, fleshy fruits about 12cm long with a mild sweet flavour.

Cultivar sourceAllotment Pro variety guide

Sweet pepper ‘Corno di Toro Rosso’ AGM

Large tapering red fruits can reach 25cm, with sweet flavour, crisp texture and thin skin.

Cultivar sourceAllotment Pro variety guide

Choose the warmest, brightest site available, ideally under cover or against a south-facing wall. Soil should be fertile, moisture-retentive and well drained. Incorporate several bucketfuls of garden compost or well-rotted manure where ground is poor or heavy, or spread mature compost as a no-dig mulch.

For outdoor plants, cover the soil with cloches for about two weeks before planting. Set ordinary cultivars 38–45cm apart and compact ones about 30cm apart. Protect young outdoor plants with cloches until the end of June where conditions are cool or windy.

Containers must be at least 30cm wide, with one pepper planted centrally in peat-free multipurpose compost. A standard growing bag can hold two or three plants. Add support canes before the root ball fills the container.

Sow indoors from mid-February to early March for plants destined for a greenhouse, or in late March and early April for outdoor cropping. Germination needs 18–21°C, supplied by a heated propagator or warm bright windowsill. Keep the seed compost evenly moist rather than saturated.

After emergence, give seedlings bright light at 16–18°C so growth remains sturdy. Once two true leaves form, move every seedling into its own 7.5–9cm pot. Maintain warmth and turn windowsill plants regularly to prevent leaning.

Pot on before plants become root-bound. Poor light, low temperature or early waterlogging slows a crop that already needs a long season. Bought or grafted plants provide an alternative where warm propagation space is unavailable; grafted plants can be more vigorous and reliable in cooler conditions.

Keep young peppers indoors until at least late May. Plant into a heated greenhouse in late April, an unheated greenhouse in mid-May, or outside in late May or June once night temperatures remain reliably above 12°C. Harden outdoor plants gradually for two weeks and plant at their original compost level.

Peppers grow best above 15°C but fruit set can decline over 30°C. Ventilate and shade greenhouses in hot weather. They appreciate humid air, so damp down the greenhouse floor during warm dry spells without keeping the root compost waterlogged.

Maintain an even water supply. Dry plants may shed flower buds and container compost may need daily watering in hot weather. Water at root level and mulch ground-grown plants. Feed container peppers weekly with an organic high-potassium liquid fertiliser from the start of flowering. Enriched ground-grown plants need less feeding, although potassium feed can increase yield.

Support the main stem with a sturdy cane. Fruit-laden side shoots are brittle, so add more canes and soft ties where a large crop develops. Pinching the main tip is optional: doing so at about 30cm can create more branches and smaller fruit, but may delay the first harvest.

Greenhouse fruit can be harvested from mid-summer into autumn. Outdoor peppers normally start in August and stop as early-autumn temperatures fall. Pick when fruits are fully swollen, firm and glossy. Cut with secateurs or a sharp knife, retaining a short stalk and supporting the brittle branch.

Harvest at green or coloured stages according to use. Green peppers are less sweet but removing them promotes further fruit development. Fruit left to turn red, yellow, orange or purple develops fuller sweetness, although it occupies the plant for longer. Pick regularly rather than allowing overripe fruits to burden the stems.

Near the end of the season, cover outdoor plants with plastic-free fleece or move pots indoors so remaining peppers can finish ripening. Discard soft or diseased fruit rather than storing it against sound produce.

Sweet peppers can be eaten raw, grilled, roasted, fried or stuffed. Remove the stalk, pale internal ribs and seeds during preparation. Round thick-walled peppers hold fillings well, while long thin-skinned types roast and char quickly.

Freshly harvested fruit keeps best cool and dry for a short period. Avoid sealing damp fruit in an airtight container. Surplus peppers can be sliced and frozen, roasted and preserved safely, or dried where the flesh is thin enough. Follow a tested food-preservation method for oils, pickles and bottled products.

Flower drop commonly follows drought, cold nights or excessive heat. Maintain even moisture, keep plants above 12°C at night, aim for more than 15°C in active growth and ventilate above 30°C. Blossom end rot appears as a dark sunken patch at the fruit base and reflects irregular calcium delivery, usually caused by uneven watering rather than deficient soil.

Inspect shoot tips and leaf undersides for aphids. In greenhouses, whitefly and red spider mite also multiply quickly; good hygiene and regular observation allow biological controls and predators to act early. Remove decaying tissues and improve airflow to limit grey mould.

Common problems