How to grow cucumbers

There are two main types of cucumbers – greenhouse cucumbers and outdoor types.

Greenhouse cucumbers need plenty of heat, so need to be grown in a greenhouse or polytunnel. They are large plants that produce long, smooth fruits, similar to those in the supermarket. They don't need pollinating and the male flowers need to be removed to prevent this happening, otherwise the fruits will end up bitter and full of seeds. Some greenhouse varieties have been bred to only produce female flowers.

Outdoor or 'ridge' cucumbers can tolerate lower temperatures and can be grown in a sunny spot outside. The fruits are shorter and fatter, with a rough, ridged skin. The flowers are pollinated by insects, so both the male and female flowers are needed. Some varieties trail and can be trained up a support or left to sprawl; bush varieties are more upright and compact and ideal for smaller spaces.

Some cucumber varieties will grow in a greenhouse or outside. It's important, however, not to grow a 'ridge' type in the greenhouse alongside greenhouse varieties, as this will result in cross pollination and bitter, seed-filled fruits.

How to grow cucumbers

Whether you're growing indoor or outdoor cucumbers, sow the seeds in late winter or early spring, or buy young plants at the garden centre in late spring. Sow the seeds into pots of peat-free, multi-purpose compost. They need a temperature of at least 20ºC to germinate. Pot seedlings on after they have developed their first pair of 'true' leaves. If growing outdoor cucumbers, harden off your plants by gently acclimatising them to outdoor conditions, after all risk of frost has passed. Tie them into a sturdy support, such as a bamboo cane, and water regularly. When your cucumbers start to flower, feed weekly with a high potash fertiliser, such as a liquid tomato food. Harvest cucumbers as and when they are ready.

More on growing cucumbers:

• How to grow cucumbers from seed
• Veg seed storage times
• How to damp down your greenhouse

Growing cucumbers: jump links

• How to sow cucumber seeds
• Caring for cucumbers
• Harvesting cucumbers
• Storing cucumbers
• Problem solving
• Buying advice
• Cucumber varieties to grow

How to sow cucumber seeds

Cucumber seeds need heat to germinate – at least 20°C – so place pots in a greenhouse, heated propagator or on a sunny windowsill for the best results. Sow in February or March if your greenhouse is heated, or in April if you have an unheated greenhouse. Fill small 5cm pots with peat-free, multi-purpose compost and sow the seeds vertically or on their sides (not flat), 1cm-2cm deep. Sow two cucumber seeds per pot, then water. You should see the seeds germinating in 7-10 days. Once the seedlings appear, remove the weakest seedling to leave one per pot. Pot seedlings on into a 9cm pot after they have developed their first pair of large 'true' leaves.

You can also sow outdoor cucumber seed directly outdoors in late May or June – wait until the risk of frost has passed. Cover the ground with a cloche or fleece after planting to warm the soil.

How to plant cucumbers

In the greenhouse, plant seedlings out when they have two or three leaves. They can be planted into greenhouse borders that have been enriched with plenty of garden compost, 60cm apart, or in growing bags – two plants per bag. You can also grow them in large containers filled with peat-free multi-purpose compost.

Train the main stem up a sturdy support, such as a bamboo cane, wire, string or trellis, tying it in if necessary.

For outdoor cucumbers, gently harden off your plants by gently acclimatising them to outdoor conditions for at least a week. Don't plant them out until early June – they need very warm conditions. Plant them out in a sheltered, sunny spot in soil that has been enriched with plenty of organic matter, such as well rotted manure or garden compost. You can grow the main stem up a support, letting the sideshoots trail along the ground, or up wire mesh. If you are going to let them sprawl, plant 90cm apart.

Never grow ridge cucumbers in a greenhouse as an 'all-female' greenhouse type – it will lead to cross-pollination, and your fruits will taste bitter.

Outdoor trailing cucumbers can be left to sprawl on the ground or the side shoots can be trained up netting or trellis. If you're going to train them, plant 45cm apart and if sprawling, 90cm apart. Bush varieties may need staking but do not need training.

How to care for cucumbers

In the greenhouse, water cucumber plants regularly and mulch the soil to retain moisture and keep the area around them weed-free. Increase humidity by damping down the greenhouse regularly, or spraying the cucumber plants with a fine mist from your hose. You could even section off an area of your greenhouse, using plastic sheeting, to further aid humidity.

• How to damp down your greenhouse

When your cucumbers start to flower, feed weekly with a high potash fertiliser, such as a liquid tomato food. Cucumbers bear male and female flowers and in the greenhouse, you will need to remove the male ones, as pollination can make the fruits taste bitter and be full of seed. You can tell them apart as female flowers have an immature fruit behind it, whereas the male ones have a normal stem. Some F1 greenhouse varieties, such as cucumber 'Bella', bear only female flowers.

Pinch out the growing tip of the plant once it has reached the top of its support to encourage side shoots (and therefore bigger crops) to form. Pinch out the tip of each flowering side shoot once the fruits begin to develop, leaving two leaves after each fruit. You can also pinch out the tips of flowerless side shoots once they reach 60cm long.

Outdoor varieties also need plenty of watering to keep the soil moist. Do not remove the male flowers on outdoor cucumber varieties – the flowers are pollinated by insects, so both the male and female flowers are needed.

Pinch out the growing tip once seven leaves have formed. You can train the side shoots up a support, or leave them to trail on the ground. You can also pinch out the flowerless tips once the stem has formed seven leaves.

How to harvest cucumbers

You can start harvesting cucumbers from around 12 weeks after sowing, in midsummer. The more cucumbers you pick, the more the plant will produce. Outdoor types will crop until September, while greenhouse types can fruit into October if it's warm. The length of the cucumbers will depend on the particular variety, so check the packet. Harvest the fruits as and when you need them, but don't leave them on the plant for too long as older fruits can taste bitter and their skins can get hard.

Harvest cucumbers early in the morning when it is cool. Cut the fruits from the plant using secateurs or a sharp knife.

Some longer cucumber varieties can be cut in half while still on the plant and left to form a callus, so they can be used later.

Watch Monty Don explain how to harvest cucumbers by cutting them in half:

How to store cucumbers

Cucumbers are generally best picked fresh and eaten immediately. They can be stored for a few days in the fridge. Smaller cucumbers can be pickled, either sliced or left whole, as gherkins.

Growing cucumbers: problem solving

Cucumber mosaic virus is spread by aphids. It's easily spotted as the leaves develop a distinctive yellow mosaic pattern. This disease will stunt the growth of your cucumber plants and affect flowering and fruiting. There's no treatment, so the only course of action if you find signs of the disease is to destroy any infected plants. You should also avoid touching other plants to stop the disease spreading.

Powdery mildew can appear on leaves as white powdery patches. These cause the leaves to become stunted and shrivel. It's often caused by under-watering, although there are cultivars available that are more resistant.

Whitefly can prey on greenhouse-grown cucumbers. These tiny white insects affect the plants by sucking sap. The honeydew they produce causes the growth of black, sooty mould, affecting the healthy growth of the plant.

Red spider mite can affect greenhouse cucumbers in warmer weather. The treatment is to burn the affected leaves which look rusty. Biological controls are also available.

Protect young seedlings against slugs and snails.

Here, Kevin Smith explains what to do if your cucumber plants lose their leaves:

Cucumber varieties to try

Greenhouse cucumbers

• ‘F1 Bella’ – an all-female flower variety, producing long, 35cm fruits. It can be grown in an unheated greenhouse and has a good tolerance to powdery mildew
  Buy cucumber 'F1 Bella' seeds from Dobies
• ‘F1 Delistar’ – a new and unusual variety with thin, pale green, translucent skin, so no need to peel
  Buy cucumber 'F1 Delistar' seeds from Suttons
• ‘Mini Munch’ – an all-female flower variety that produces very small but tasty 7cm fruits
  Buy cucumber 'Mini Munch' seeds from Thompson & Morgan

Outdoor cucumbers

• 'Marketmore' – a ridge cucumber with short, dark fruits
  Buy cucumber 'Marketmore' seeds from Dobies
• 'Venlo Pickling' – can be used in salads or for pickling
  Buy cucumber 'Venlo Pickling' seeds from Suttons
• 'Bush Champion' – a compact, bush variety, ideal for small spaces
  Buy cucumber 'Bush Champion' seeds from Suttons

Greenhouse and/or outdoor cucumbers

• 'F1 Burpless Tasty Green' – this popular, easy-to-grow ridged cucumber can be grown indoors or outside. Produces 25cm cucumbers with very high vitamin levels
  Buy cucumber 'Burpless Tasty Green' seeds from Thompson & Morgan
• F1 ‘Swing’ – an all female flowering variety can be grown in a greenhouse or outdoors. It produces a heavy crop of long, crisp cucumbers
  Buy cucumber 'F1 Swing' seeds from Thompson & Morgan
• ‘La Diva’ (all-female) can also be grown in a greenhouse or outdoors. It produces a prolific crop of chunky, seedless cucumbers
  Buy cucumber 'Diva'seeds from Thompson & Morgans
• 'Crystal Lemon' – unusual, round, pale yellow fruits
  Buy cucumber 'Crystal Lemon' seeds from Thompson & Morgan
• 'Wautoma' – a prolific cropper that can be harvested small for pickles or left to grow for use as a slicing cucumber
  Buy cucumber 'Wautoma' seeds from Real Seeds