RHS Growing Guides
How to grow cucumbers
Our detailed growing guide will help you with each step in successfully growing Cucumbers.
Getting Started
Home-grown cucumbers are unbeatably fresh and crunchy, perfect for adding to summer salads.
Cucumbers (Cucumis sativus) are closely related to courgettes, squashes and pumpkins, and are grown in a similar way to their fellow cucurbits, so if you’ve had success with these, you should find cucumbers straightforward too.
Month by Month
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Choosing
There are many cucumber varieties to choose from, varying in fruit size, flavour and disease resistance. Small or mini cucumber varieties produce lots of fruits, which are ready to harvest more quickly than longer ones. There are also varieties with tiny fruits (gherkins) for pickling. There are indoor varieties for growing in greenhouses, polytunnels or large coldframes, and outdoor varieties (or ridge cucumbers) for growing in a sunny, sheltered spot. Greenhouse varieties crop for a longer season, from mid-summer through to early autumn. Outdoor varieties are weather dependent, starting to fruit later and finishing earlier, but should still produce a good crop in warm conditions.
When choosing, look for varieties that have an RHS Award of Garden Merit (AGM), as these performed well in our trials – see our list of AGM fruit and veg and our Recommended Varieties below. You may also find cucumbers growing in the veg areas of the RHS gardens over the summer months, so do visit to compare varieties and pick up growing tips.
What and where to buy
Cucumber seeds are widely available in garden centres and from online suppliers. You can also buy young cucumber plants or plug plants in spring and early summer in garden centres and online. This is often a good option if you only want one or two plants.
Grafted cucumber plants have recently become more readily available, mainly from online veg seed/plant suppliers. These are very vigorous plants and should produce a larger crop over a longer season. They are more resistant to soil-borne diseases, so are useful for growing in the same ground (such as a greenhouse border) year after year. However, grafted plants are more expensive and there’s only a limited choice of varieties.
Recommended Varieties
Greenhouse variety - produces a large crop of long, straight fruits with a good crunch. Good disease...
Greeenhouse variety – medium-sized fruits with thin, translucent skin that is easy to digest.
Greenhouse/outdoor variety – predominantly female flowers. Reliable crop of large, tasty fruits.
Preparing the Ground
Cucumbers can be grown indoors in a greenhouse or polytunnel border, or outdoors in a warm, sunny, sheltered spot. Prepare each growing site by digging in two bucketfuls of home-made garden compost or well-rotted manure. Ideally do this a few weeks before sowing or planting, to allow the soil to settle. Alternatively, if you are practising no-dig, mulch the surface of the soil at each site ahead of sowing or planting directly into the mulch. Space your growing sites 30cm (1ft) apart.
Cucumbers can also be grown in containers at least 30cm (1ft) wide and deep, filled with peat-free multi-purpose compost.
Sowing
Cucumbers are best sown indoors, as they can be started off earlier and will start to fruit sooner. Germination is also more reliable and the seedlings are protected from slugs, snails and poor weather. They should be moved to their final growing position after about a month, once they are growing strongly. Seeds of outdoor varieties can also be sown outside in milder locations, once the soil has warmed up in early summer.
Sowing indoors
Keep cucumber seedlings warm and well watered, with support to keep them upright
The process is simple – fill 10cm (4in) pots with peat-free seed compost, water well, then sow one seed in the centre of each, 1–2cm (½–¾in) deep. Ideally position the seeds on their side. Put the pots in a heated propagator at 21°C (70°F) or cover with a clear plastic bag and place on a warm sunny indoor windowsill. Once seedlings appear, after a week or two, remove from the propagator or remove the covering. Continue to keep the young plants warm, in bright light, and watered regularly. For more sowing tips, see our guides below.
Sowing outdoors
Seeds of outdoor cucumber varieties can be sown directly into their growing position in late May or early June, especially in warmer parts of the UK or if the weather is particularly mild. Prepare your sowing sites in advance (see above) and sow up to three seeds together, 1–2cm (½–¾in) deep, to allow for failures.
If multiple seeds germinate in one site, remove the weaker ones to leave just one strong seedling. After sowing, cover with cloches or plastic-free fleece to keep the soil warm, and leave the covering in place after germination to help the seedlings get off to a strong start. Protect them from slugs and snails, especially in damp weather.
Planting
Plant indoor-sown or newly bought cucumber plants into their final growing site in late spring or early summer, depending on where they will be growing:
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Greenhouse cucumbers – from late May, plant into a greenhouse border or large pots once the temperature inside is consistently above 12°C (53°F). Or, if you have a heated greenhouse, you can plant as early as late March.
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Outdoor cucumbers – harden off seedlings carefully, to acclimatise them to outdoor conditions, before planting out from early June onwards, once your local temperatures are reliably above 12°C (53°F).
Planting cucumbers is very straightforward – water them well beforehand and try not to disturb the rootball, so they settle in quickly without a check in growth:
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To plant in a container – choose a pot that is at least 30cm (1ft) wide and deep, and fill with peat-free multi-purpose compost. Position one plant in the centre, firm it in gently and water generously, then add suitable supports (see below). Alternatively, plant two cucumbers in a standard-sized growing bag.
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To plant in the ground – plant one cucumber plant into the centre of each prepared growing site (see above), spacing them 30cm (1ft) apart. Firm in gently then water well. Add supports (see below) if you want to train the plants vertically.
Putting up supports
Grow cucumbers up supports to make best use of valuable ground space
Put the supports in place at planting time so their tendrils have something to cling to. The stems need tying in initially, and may need help later if they lose their way or come loose, especially outdoors and when carrying fruit.
The type of support you need depends on where you are growing your plants:
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Greenhouse cucumbers – insert a tall, sturdy bamboo cane that reaches up to the greenhouse roof, or attach a vertical wire or string from the roof, secured at ground level. Horizontal supports may also be required for side-shoots
- Outdoor cucumbers – build a wigwam or other structure from tall bamboo canes, or use stout netting supported vertically on upright stakes. Cucumbers will also climb up trellis or wires attached to a wall or fence.
If you plan to leave your cucumber plants to trail over the ground, it can be helpful to lay plastic-free weed-suppressing membrane over the soil after planting. This helps to keep fruit clean and prevent rotting, and is much easier than protecting each fruit individually when growing small-fruited varieties that crop heavily.
Plant Care
Cucumbers, whether grown outdoors or in a greenhouse or polytunnel, need warmth and regular watering to crop well. When grown in containers, plants also benefit from regular feeding.
Watering
Water greenhouse and container plants regularly, especially when fruits are forming, aiming to keep the soil or potting compost evenly moist. During hot spells, they may need watering daily. Outdoor plants growing in the ground should need less regular attention, especially if you mulch the soil, but will still need watering in dry weather in order to grow and crop well.
Take care to water at the base of the plants and try not to wet the leaves, as that can encourage fungal diseases such as powdery mildew. Use rainwater from a butt whenever possible, and water at cooler times of the day, ideally in the morning. For more water-wise tips, see our guides below.
Mulching
Lay a thick layer of mulch over the soil around the base of cucumber plants to help hold moisture in the ground, reduce the need for watering, and deter weed germination. Use home-made garden compost or well-rotted manure, but leave a gap around the base of the stem, to prevent rotting.
Feeding
Cucumbers growing in the ground shouldn’t need feeding, unless the soil is very poor. Plants in containers should be fed every 10–14 days with a general liquid fertiliser. Once they start flowering, change to a high potash liquid fertiliser such as tomato feed, to encourage flowering and fruiting.
Pinching out shoots
It’s a good idea to restrict the vigorous growth of cucumbers, so they concentrate on making fruit rather than growing too large. The method differs depending on where you grow your plants:
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Greenhouse cucumbers – pinch out the growing point when it reaches the greenhouse roof. Also pinch out the tips of side-shoots two leaves beyond a female flower (which has a tiny fruit behind it). Pinch out the tips of flowerless side-shoots once they reach 60cm (2ft) long
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Outdoor cucumbers – pinch out the growing tip once plants have developed seven leaves, to encourage side-shoots. Also pinch out the tips of flowerless side-shoots after seven leaves
Removing male flowers
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Greenhouse cucumbers – most greenhouse varieties are all-female (check seed packets for details), producing almost exclusively female flowers (with a tiny fruit behind them). These must not be pollinated, otherwise the resulting fruits will be bitter. Occasionally male flowers (without a tiny fruit behind them) may appear and need removing
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Outdoor cucumbers – outdoor varieties produce both male and female flowers. The female flowers need to be pollinated in order to produce fruit, so don’t remove the male flowers
Greenhouse heat and humidity
Greenhouses can get extremely hot in summer, so put up shading to keep temperatures from becoming damaging, ideally between 18–25°C (64–77°F).
Harvesting
Harvest cucumbers just before you want to eat them, for maximum flavour and a firm, crunchy texture
Fruit size varies according to the variety. In general, mini cucumbers should be picked at about 8cm (3in) long, small-fruited varieties at 15cm (6in) and full-sized varieties at 20–25cm (8–10in). The fruits should be uniformly green and firm, usually with a slightly rounded tip. Cut the stem cleanly with a sharp knife or secateurs, rather than pulling. Fruits can grow rapidly, so check them every few days to get them at their best. If they turn yellowish, bulbous or soft, they are likely to be over ripe.
Problems
Although usually vigorous and fruitful, cucumbers can be weakened by powdery mildew and red spider mites, especially in a greenhouse and if humidity is low. Mildew-resistant varieties are available. Mosaic virus is a more serious problem, and affected plants should be destroyed. See Common problems below for advice on how to spot and tackle these issues.
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