Hartley Magazine

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How to Grow Peppers

AGV-peppersPeppers are great fun and easy to grow. Follow our back to basics guide and you’ll be enjoying fiery pizzas and sauces or mild tasty dishes with the distinctive twang of sweet pepper by midsummer

Chilli and sweet peppers are such a diverse bunch; they are colourful crops and the assortment of shapes and sizes is a treat to behold in the greenhouse or on the open plot. The flavours are just as diverse, ranging from mild and sweet to eye-wateringly hot so there is sure to be something to suit everyone‘s tastes among the hundreds of varieties available from seed catalogues and specialists.


Peppers are much easier to grow successfully than some other greenhouse crops such as aubergines and cucumbers and since they are self-fertile are virtually guaranteed to set a good crop. In the KG greenhouse last year, despite a very poor summer there were no problems with fruit setting and of course even if a lack of sunshine means that the fruit is late to ripen, peppers can be enjoyed unripe. There is also very little, if any training, unlike cucumbers and tomatoes which need support and regular attention. Peppers do, however, require a reasonably long growing season to produce best results and sowing early will give them that. Sow seeds in seed or cell trays (modules) using fresh multipurpose or seed compost. Since peppers, particularly the chillies, can be quite prolific, why not sow just a few seeds of each variety; each has its own unique flavour and it can be great fun to try lots of different ones to be able to pick fruit in a range of shapes and colours.

Fill your tray and water the compost well before sowing your seeds on the surface. Cover with 6mm (1?4in) of sieved compost, fine sand or vermiculite before spraying over with a fine mist of water or watering with a watering can fitted with a fine rose to wet the surface. If you wish you can add a copper-based fungicide to the water such as Murphy Traditional Copper Fungicide to prevent damping-off disease. Label your tray and place in a heated propagator or on a heated bench set to 15-20C (60-68F). Cover with a propagator lid until the seedlings germinate, but remove it once most of the seedlings are through to prevent stretching and move the tray to the greenhouse bench or a sunny windowsill to grow on at a lower temperature – 10C (50F) is ideal.

Growing on

Once the plants are well established and the roots starting to fill the compost in the cells they can be moved on into 10cm (4in) pots filled with potting compost. By this time they may benefit from staking; give each a split cane and secure it with a soft wire ring or some soft string. Space the plants out on the bench as they develop so that each has as much light as possible and maintain watering, allowing the surface of the compost to dry out between each watering. Pot on into 15-20cm (6- 8in) pots once the smaller containers are full of roots, but before the plants become potbound and suffer a growth check. Plants do not require pinching or training since once they start to flower the stems tend to branch naturally, however if plants do start to stretch the growing points can be removed once they are 30cm (12in) tall. As the fruit develops, plants canbecome top heavy and this is a particular problem with large sweet peppers. Change the split cane for a bamboo one or similar if necessary to keep plants upright.

Outdoor crops

Plants can be grown outdoors in mild areas. Grow as described above, planting out once all fear of frost has passed and the soil has warmed. June is usually suitable in most areas – early June in the south, late June in the north. Plants must be hardened off thoroughly prior to planting – gradually acclimatising them to conditions outside. Plant in a sheltered, sunny site in well-drained, reasonably fertile soil which was manured the previous autumn.


Although peppers are not as hungry as tomatoes, they do need regular feeding to keep them healthy and productive. Feeding with a high potash liquid fertiliser mixed at half strength every watering ensures that plants always have plenty of nutrients. Feeding need not start until three weeks after potting on, since the compost will contain all the minerals your plants need until then.


You can choose to harvest the fruit when unripe and green or fully ripe and ‘coloured up‘. It‘s at this stage that chilli peppers are at their hottest and sweet peppers their sweetest. Peppers can be stored in a number of ways – slowly dried in a cool oven (or in sunshine if we get any), sliced, roasted and stored in oil, frozen or of course used fresh. If dried and stored in airtight jars they should last for up to a year – in time for your next harvest!

Pests and diseases

Belonging to the same family, peppers suffer from some of the same pests and diseases as tomatoes.

  • Whitefly – little white moth-like pests may infest the leaves. Adults and larvae suck the sap giving rise to black sooty mould which covers the fruit and foliage below the feeding pests. Hang sticky yellow traps in the greenhouse to catch flying insects and spray with a suitable insecticide. Alternatively combine traps with a biological control using the predatory encarsia wasp.
  • Aphids – often the first pests to trouble peppers early in the season and will suck the sap from the shoot tips causing distortion and spreading viruses. Spray as soon as the pests are seen or rub them off with finger and thumb.
  • Red spider mite – may infest the tips of the plants later in the summer causing a severe loss of vigour and yellowing leaves. Spray or introduce the predator phytoseilius at the first sign of attack. Misting over the leaves with water deters their spread.
  • Botrytis (grey mould) – will attack the ripening fruit and any damaged tissue such as leaf scars left by falling leaves. Pick up fallen leaves regularly and remove damaged fruit. Give plants plenty of space and ventilate the greenhouse or polytunnel to improve air circulation.


There are literally hundreds of varieties available of both sweet and chilli peppers. Most catalogues rate the chillies in order of heat often on a scale of one to 10. Others use the Scoville Heat Unit scale (SHUs). Most sweet peppers register ‘0’ on the scale and the hottest chillies such as the very hottest ‘Bhut Jolokia‘ registers at one million SHU. Generally speaking the smaller the chilli, the hotter it is, so be warned! Among the sweet peppers look for those suitable for stuffing with rice or cream cheese such as:

  • ‘Corno di Torro Rosso‘: Long, thin-walled red fruit with a sweet taste.
  • ‘Tasty Grill Red F1’: Earlyripening, 25cm (10in) red fruit.
  • ‘Tasty Grill Yellow’: As above, but ripening to yellow.


Cell trays are often better for raising plants than traditional seed trays since they prevent the root disturbance caused by pricking out the seedlings later. They also save time, but more importantly since each seedling is isolated from the others, cell trays can help to inhibit the spread of damping-off disease – a common cause of losses when raising plants from seed.