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Chilli Seed Sowing & Growing Advice

When to Sow

Sow Chilli seeds 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 27°C-32°C, although some can grow if temperatures are above 21°C 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 36°C 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.

How are Chilli Peppers Pollinated?

Chillies are usually self-pollinating but additional assistance whether from wind, insects, bees or artificial pollination (hand pollination) has been shown to improve flower set and increase the peppers yield.

In the UK most chillies are grown in a greenhouse so there is little wind pollination & the number of insects/bees are lower than in the garden so artificial hand pollination will help. Simply use the tip of your finger or a small artist brush to move the pollen from one flower to the next. This is what insects do naturally as they fly from one flower/plant to another carrying the pollen on their bodies.

Chilli flowers are also prone to falling off prematurely and one of the reasons this happens is because pollination has not occurred so hand pollination can help. See below for some other reasons flowers drop prematurely.

Why are my chilli flowers falling off?

It is quite usual for a few chilli flowers and their stalks to fall off at the early stages of development. However if numbers are high there could be some underlying problems.

Temperatures – chillies are from very warm climates and it can be a struggle to provide them with consistently high temperatures through the season. The flowers are more likely to drop if the temperatures are either too low below 10°C or too high, above 32°C.

Water – overwatered or underwatered chilli plants will cause premature flower drop. We let our chillies dry out on top before watering although if the greenhouse is warm and the day will be hot, we will water as lack of water causes stress and flower/leaf drop. Soil or compost that is too wet will mean the chilli roots will be unable to work properly & this stress may cause flowers to drop.

Poor pollination – chillies are self-fertile and usually do a good job themselves but it has been proven that a helping hand from wind, insects, bees or hand pollination can help fruit set and increase chilli pepper yields. Hand pollination is especially useful in the UK where majority of chillies are grown in the confines of a greenhouse and wind & insect activity are lower then in the garden. It is easy to hand pollinate with use of  a finger tip or artists paintbrush, when the flower is fully open, brush the pollen with the finger tip/brush and then brush that finger/brush onto another flower. It does not matter if you move onto another plant (unless you wish to save the seed and breed identical chillies the following year, in which case the chilli plants should be kept in isolation anyway).

Fertility – chillies need well-balanced fertility. Potassium, a nutrient that helps the fruit to form is especially needed to help fruit set, if the soil/compost is lacking in Potassium the flowers will drop and the chillies will not set. A Potassium rich fertiliser like Tomorite or a seaweed fertiliser will help and these are generally given as soon as the first flowers begin to set and either once a week or fortnightly depending on manufacturers instructions. If used before flowering it can cause a growth of foliage at the expense of fruitsand do not be tempted to over fertilise the chillies as this can also cause flowers to drop.

It sounds quite complicated but just take care with watering, feed with Potassium rich fertiliser as per manufacturers instructions and hand pollinate. Make sure greenhouse is ventilated especially on hot days & close door at night if temperatures are cold.