How to grow cucumbers and best varieties

Cucumbers are relatively easy to grow, either in an unheated greenhouse or in a sunny spot outside. You can even grow some varieties in a hanging basket. There's no need to have slimy cucumbers at the back of the fridge as you can now grow snack-size fruit that are perfect for lunchboxes.

The Which? Gardening magazine research team have grown and tasted a range of different varieties to bring you our Best Buy varieties. We also share our tips about how to grow them.

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How to grow cucumbers: month by month

Best cucumber varieties

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Snack-size cucumbers

Outdoor cucumbers

Outdoor cucumbers for containers

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How to grow cucumbers

When to sow cucumber seeds

Sow cucumbers for growing in greenhouses or polytunnels from mid- to late April, or up to mid-May in the North. For cucumbers for growing outdoors, sow in mid- to late May.

Use 5cm pots or large modules and sow singly into a Best Buy compost for sowing seeds. Seeds need to be at 20°C or more for germination; sow in a greenhouse, in a heated propagator or on a windowsill indoors. Pot on into a Best Buy compost for raising young plants once seedlings have their first true leaves, and keep warm until they have about five leaves. Be careful not to overwater them or the plants can rot and die.

Growing cucumbers in a greenhouse or polytunnel

Plant into growing bags or pots (10-litre or larger) of Best Buy compost for containers mixed with a Best Buy controlled-release feed in a greenhouse or polytunnel and train as cordons up supports or strings tied to the greenhouse frame. 

Should I pinch out cucumber side shoots?

Pinch out side-shoots as the plants grow, and allow the plants to trail downwards once they reach the top of the supports.

Learn how to buy the best greenhouse

Growing cucumbers outdoors

Outdoor cucumbers can be planted in a sunny spot outside once the danger of frost has passed in late May or early June.

Outdoor cucumbers need very little attention. After transplanting you may want to cover plants with fleece, if there are still some cold winds. Keep the area weed free and watch for the first fruits from late July. Once fruiting begins and if afternoon temperatures are above 22°C, you can expect five fruits or more every week, mainly in August.

Discover our best frost protective covers

Growing cucumbers in a hanging basket

New breeding has produced small cucumber plants that are suitable for growing in hanging baskets. Put one plant per 30cm basket, using a Best Buy compost for containers mixed with a Best Buy controlled-release feed. Hang up the basket in a sunny spot outdoors and let the tendrils hang down without bothering to support them. The fruit are easy to find and should be picked when they're about 10cm long.

Growing outdoor cucumbers in pots

When we grew outdoor cucumbers in containers, we found that the plants in 30-litre containers produced one and a half times more cucumbers than those in 15-litre pots; choose a 30-litre container to maximise your harvest. 

Watering and feeding

Keep well watered – cucumbers are thirsty – and feed with a liquid fertiliser, such as tomato feed if you didn’t incorporate a controlled-release feed into the compost at planting time.

Make things easier with a best garden irrigation system

How and when to harvest cucumbers

Harvest in: July to October

Pick cucumbers before you see any decrease of dark green in the colour. Paler skin suggests seed development, with flesh becoming harder and less sweet. Regular picking encourages development of more fruits, so it's worth checking every day undercover and every two days outside.

Outdoor cucumbers usually finishing cropping in September, but indoor plants carry on until early October.

Try our best secateurs

Common cucumber growing problems

Slugs and snails

Slugs and snails can munch through young plants. Protect with ferric phosphate slug pellets or an organic slug and snail control.

Read more about how to get rid of slugs and snails.

Bitter fruits

Cucumbers can become bitter on varieties that produce both male and female flowers when insects transfer pollen from the male to female flowers. Remove male flowers as soon as they appear; female flowers have a bulge like a tiny cucumber behind the flower head. Growing all-female varieties avoids this problem.

Powdery mildew

Powdery mildew is the main problem to watch out for. Remove affected leaves, don’t overcrowd plants, ensure they’re well watered and avoid wetting the leaves when you water.

Read more about how to treat powdery mildew on plants.

Red spider mite

Red spider mites can cause speckled and yellowing leaves; watch out for the fine webbing they produce, too. They can be controlled with a biological control, such as phytoseiulus or amblyseius. These predatory mites will feed on the pest and deal with the problem for you. 

Read more about how to get rid of red spider mites.

How we test cucumbers

We grew different varieties of cucumbers and harvested fruits two to three times a week, recording the number and weight of cucumbers for each variety and rating them for quality. We also rated the varieties for ease of picking, flavour and whether they succumbed to powdery mildew.