Sow Chillies in a greenhouse from early February to April. They need warmth and a long period of time to fruit. They can be sown outside from early April in warmer southern parts of the country but they will need lots of sustained heat to produce a good crop, so it is better to sow indoors.
Chillies originate from South America so they like it hot and their optimum germination temperature is between 27oC-32oC, although some can grow if temperatures are above 21oC but germination is more erratic.
Use a loam based seed & potting-on compost as chillies like good drainage. A number of seeds can be sown into a seed tray or pot 5mm deep and then pricked out and potted on when 2 true leaves have grown. (True leaves are the second set of leaves to form). The plant should be carefully lifted by the true leaves and not the stem to prevent damage. I support the root system by holding a plant label underneath whilst holding the true leaves. Best results are achieved by placing the tray/pot into a thermostatically-controlled propagator but they will also germinate with the use of a heated tray/mat. They can then be potted on into a 9cm pot until they reach a height of 8cm-15cm tall and then finally re-potted into a 3L/4L pot or straight into the ground if there is open soil in your greenhouse/polytunnel.
Shading may be needed to control the temperature in your greenhouse as if temperatures are above 36oC the flowers may drop off and the fruit will not set. It is a good idea to mist the greenhouse twice daily to maintain humidity.
Chillies are better watered from the top with a spray bottle but they do not like to be over or under-watered.
Flowering/Fruiting
They naturally branch into 2 or more stems with a flower bud at the joint, to encourage the plant to bush out pinch out the tip when it reaches 20cm. When the plants start to fruit feed them weekly with a potassium rich feed (like a tomato feed) to encourage good fruit.
Harvesting
Fruits that start green or yellow usually ripen to red but some green chillies will mature to orange or yellow. Green fruits can be harvested and are milder in flavour then the red. They are ready to pick when they are firm and glossy and the sooner picking begins the more productive the plant will be. (Excess produce can be frozen, pickled or preserved in oil for use later). Harvesting usually begins in August through to October although if conditions are still warm enough fruits can still be growing into December.
Support
Some chillies may need additional support especially if they are laden with fruit a small cane inserted by the stem and tied to it is usually enough.
Pests & Diseases
Chillies belong to the same family as tomatoes (Solanaceae - potato family) and suffer the same pests & diseases.
Greenfly/Whitefly - when the plants produce lush new growth they become vunerable to these aphids that spread viruses quickly and lead to the detrement & health of the plant. The organic method is best to just hand pick them off, introduce ladybirds or a parasitic wasp (Encarsia Formosa) that can be purchased by specialists over the internet. The latter methods of biological control is only successful in greenhouses/polytunnels that can be sealed. Can be treated with Savona or insecticidal soap aswell.
Botrytis - may also pose a problem especially at the base of the plant and the fruit. It begins as a brownish spot that develops into a grey mould. It is particularly prevalent when it is cold & damp. Good ventilation will help stop this occurring, removing all dead or injured plant material before it becomes infected (good housekeeping). Remove all infected material by cutting back into healthy stock and burning or binning the infected stem. Do not compost diseased plant material. Isolate infected plants to prevent the disease spreading.
Potato Blight - may also affect plants particularly if grown outside. It thrives in damp wet summers. It is a fungal disease that spreads rapidly and it is best to burn infected plants straight away. The first signs of infection are brown/black patches at the tips & margins of leaves. In moist weather a white fungal growth develops on the underside of leaves. The brown patches may also develop on the stem and the disease spreads to the rest of the plant leading to its collapse.
Thrips - this produces a silver white discolouration with tiny black dots (this is the insect's excrement) on the upper leaf surface. The leaves become distorted and flower and fruit production is affected. It likes hot, dry conditions so water regularly and regulate the temperature with shading and ventilation.
Blossum end rot - this is a calcium deficiency(add limestone/bonemeal when planting the plant if this has been a problem in the past) and causes a brownish patch to appear on the end of the fruit. This is really only a problem with soil grown chillies.
