Few summer crops earn their place quite like the cucumber. Crisp, cooling and endlessly versatile, a healthy cucumber plant or two can keep a household in salads, sandwiches and pickles from midsummer right through to early autumn. The good news is that growing cucumbers is far more reliable than many gardeners expect, and learning how to grow cucumbers in the UK comes down to giving these tender plants the warmth, moisture and rich soil they crave.
There are two broad routes to take, and choosing the right one is the single most important decision you will make. Greenhouse (or indoor) cucumbers are smooth-skinned, long and reliable, and the modern all-female F1 types crop heavily without any fuss over pollination. Outdoor, or ridge, cucumbers are more robust, shorter and a little knobbly, and they happily grow up a support or trail across a raised bed. Both can be raised from cucumber seeds on a warm windowsill or in a greenhouse, or bought as young plants if you only want one or two.
Growing cucumbers in the greenhouse
A greenhouse is the cucumber's natural home. The warmth and shelter under glass let you start earlier, crop for longer and grow the sweeter, thin-skinned indoor varieties that struggle outside in a British summer. Greenhouse cucumbers will fruit from midsummer through to early autumn, well beyond the shorter outdoor season. Even a compact patio greenhouse gives you enough warmth and height to grow a productive plant or two, and a little shading or a blind helps keep temperatures in the ideal 18 to 25C range when the sun is at its fiercest.
Growing cucumbers from seed
Raising cucumbers from seed is cheap, satisfying and gives you the widest choice of varieties. For a heated greenhouse you can sow from mid-February, while an unheated greenhouse or polytunnel is better sown in March or April once the worst of the cold has passed. Cucumber seeds need real warmth to germinate, ideally 20 to 25C, so a heated propagator or a warm windowsill makes all the difference.
Fill 10cm pots with peat-free seed compost, water well, then sow one seed per pot. A useful trick is to sow the seed on its edge rather than flat, roughly 1 to 2cm deep, which helps water drain off the seed and reduces the risk of rotting. Cover with a clear bag or pop the pots in a propagator at around 21C, and seedlings should appear within a week or two.
Once they germinate, keep the young plants warm, bright and evenly moist. Greenhouse shelving or a seedrack lifts the pots off a cold floor and keeps them close to the light, which young cucumber plants need plenty of to grow sturdy rather than leggy. As soon as the roots fill their pots, pot them on into larger containers so growth never stalls before they reach their final home.
Growing cucumbers from young plants
If you only want one or two plants, or you missed the sowing window, buying young cucumber plants from a garden centre or online supplier is a perfectly good shortcut. They are usually sold in spring and early summer, and grafted plants are also increasingly available, prized for being extra vigorous and more resistant to soil-borne disease.
Whichever you choose, plant greenhouse cucumbers into their final position in late spring, once the temperature inside is reliably above 12C. They thrive in grow bags (two plants to a standard bag), large pots at least 30cm wide and deep, or a greenhouse border enriched with plenty of well-rotted compost. Stand pots on staging or at the foot of the glass where they can climb, water them in well, and try not to disturb the rootball so they settle in without a check.
Training, care and how to harvest
Cucumbers are climbing plants, so train them upward to save space and keep the fruit clean. Tie the main stem to a tall cane or, better still, a vertical string fixed to the greenhouse roof and anchored at the base, winding the growing stem around it as it climbs. Pinch out the growing tip once it reaches the roof, and pinch out the tips of side-shoots two leaves beyond a developing fruit to keep the plant productive rather than rampant.
Female & Male Cucumbers!
The question of flowers trips up many growers. Most modern greenhouse varieties are all-female F1 types, which means almost every flower sets a fruit and you never need to worry about pollination. With these, you should not let the flowers be pollinated at all, as that is what turns the fruit bitter and seedy. If you are growing an older, non-all-female variety, you will see male flowers (those without a tiny fruit behind them) and should pinch these out to prevent the females being pollinated. Check the seed packet if you are unsure which type you have.
Beyond that, the routine is simple: warmth, humidity and a steady supply of water. Keep the compost evenly moist, watering daily in hot spells, and damp down the greenhouse floor on warm days to raise humidity, which also helps deter red spider mite. Feed every 10 to 14 days once flowering begins, switching to a high-potassium tomato feed (like Tomorite) to drive fruiting. Collecting rainwater in a water butt gives you a free, soft supply through the thirsty summer months.
Start harvesting from July, and keep picking regularly through to September. Cut fruits cleanly with a sharp knife or secateurs when they reach the full size for the variety, which is around 8cm for mini types, 15cm for small-fruited ones and 20 to 25cm for full-length cucumbers. The more you pick, the more the plant produces, so a single healthy greenhouse cucumber plant can give you ten to twenty fruits or more over a good season. Never let them sit and turn yellow or bulbous, as that signals the plant to stop cropping.
Growing cucumbers outdoors and in raised beds (from seed and plants)
If you have no greenhouse, do not be put off. Outdoor or ridge cucumbers are tougher, more weather-resilient plants, bred to crop in a sheltered British garden. They are insect-pollinated, so unlike all-female greenhouse types they carry both male and female flowers and you simply leave them be. A raised bed is an excellent home for them, as the soil warms faster in spring and you can fill it with the rich, free-draining, moisture-holding compost cucumbers love. A metal raised bed will not rot or harbour pests the way timber can, and the extra height makes watering and harvesting easier on the back.
When to sow and plant cucumbers outdoors
If you can, outdoor cucumbers are still best started under cover for a head start. Sow seed indoors in April or early May at 20 to 25C, using the same on-edge method as for greenhouse types, then harden the young plants off gradually before planting out from early June, once the last frost has passed and night temperatures stay reliably above 12C. In milder parts of the country, you can also sow seed directly into warm soil outdoors in late May, dropping two or three seeds at each station and thinning to the strongest. Our monthly seed sowing guide is handy for keeping the rest of the veg patch on schedule alongside your cucumbers.
Where to position them
Cucumbers are sun-lovers, so choose the warmest, sunniest, most sheltered spot you have. A south-facing position against a fence or wall is ideal, as it traps heat and offers protection from wind that could otherwise batter the leaves and snap the stems. Avoid frost pockets and exposed, draughty corners, and remember that these are tender plants with no tolerance for cold: a single late frost will finish them off, which is why early June is the safe moment to commit them to the open garden.
Watering, soil, spacing and support
Before planting, work two bucketfuls of well-rotted manure or garden compost into each growing site, or fill your raised bed with a generous, fertile mix. Cucumbers are hungry, thirsty plants that resent dry roots, so the richer and more moisture-retentive the soil, the better they crop. A mulch around the base helps lock in moisture and keep weeds down, but leave a small gap around the stem to prevent rotting.
Space plants around 30 to 45cm apart, or 30cm apart if growing them up a single support. You can either let outdoor cucumbers trail across the ground, which works well over weed-suppressing membrane to keep the fruit clean, or train them up a wigwam of canes, sturdy netting or a trellis to save space. Growing them vertically keeps the fruit off damp soil and away from slugs. For trailing plants grown outdoors, pinch out the main growing tip once the plant has around seven leaves to encourage fruitful side-shoots. Water consistently, especially as fruits swell, and aim to water the soil rather than the foliage to reduce the risk of mildew.
Cucumber companion plants
A little companion planting helps an outdoor cucumber patch thrive. Cucumbers grow happily alongside climbing beans and peas, which fix nitrogen in the soil, and they make classic partners for sweetcorn, where the tall stems offer light support and shelter. Nasturtiums are a useful trap crop that lures aphids away from your cucumbers, while dill and other umbellifers draw in the hoverflies and lacewings that prey on those same pests. Low-growing herbs and flowers such as borage also bring in pollinators for outdoor varieties. These pairings are widely recommended by the RHS and long-standing companion-planting sources, and a few minutes of planning when you lay out the bed pays off all season.
It pays to know what to keep apart, too.
Top Tip: Avoid planting cucumbers near potatoes, which compete heavily and can make plants more prone to disease, and keep strongly aromatic herbs such as sage well away, as they are thought to suppress cucumber growth and can taint the flavour.
When and how to harvest
Outdoor cucumbers start a little later than greenhouse plants but still crop generously from midsummer. Begin picking in July and keep going through to September, harvesting every couple of days once fruits start to swell. Cut each cucumber cleanly with a sharp knife when it reaches the full size for its variety and is firm and evenly green, rather than waiting for the biggest possible fruit. Picking little and often is the secret to a long, heavy crop, as leaving mature fruits on the plant quickly slows production. If you spot a cucumber turning yellow or going soft, remove it straight away to keep the plant cropping.
Cucumber pests and problems and how to avoid them
Cucumbers are vigorous and usually trouble-free, but a handful of issues are worth watching for, and most can be headed off without reaching for chemicals.
Red spider mite is the classic greenhouse pest, thriving in hot, dry air and leaving leaves mottled, bronzed and webbed. The best defence is prevention: keep humidity up by damping down the floor on warm days, and improve ventilation. Powdery mildew, a white dusty coating on the leaves, is the other common greenhouse problem and is encouraged by dry roots and wet foliage, so water consistently at the base and choose mildew-resistant varieties where you can. A little shading to keep the greenhouse from overheating helps with both.
Whitefly and aphids both suck sap, weaken plants and spread disease, and tend to cluster on the undersides of leaves. Encourage natural predators such as ladybirds, lacewings and hoverflies, blast small infestations off with water, and use a soft soap spray if numbers build. Outdoors, nasturtiums planted nearby act as a useful decoy. Cucumber mosaic virus is more serious: it causes yellow mottling, distorted leaves and stunted growth, is spread by aphids, and has no cure, so controlling aphids and removing and destroying any affected plants promptly is the only real answer.
Finally, bitterness. With all-female greenhouse varieties, bitter fruit is almost always the result of unwanted pollination, so keep male flowers out of the greenhouse and check your variety. Bitterness can also be triggered by stress, particularly irregular watering and big swings in temperature, so the steady warmth, humidity and moisture cucumbers prefer are also your best insurance against a disappointing crop.
Cooking with cucumbers
A glut of homegrown cucumbers is a happy problem, and they are far more than salad filler. For something quick and a little different, Rhino's resident chef Gill Meller swears by his bashed cucumbers with green chillies, a punchy, fresh salad where the cucumbers are crushed so the craggy pieces soak up a dressing of sesame, tamari, cider vinegar and herbs. It is wonderful on its own or alongside steamed fish, seared scallops or crispy duck, and is a brilliant way to use a few sweet, just-picked fruits.
Beyond that, homegrown cucumbers shine in a simple cucumber and dill salad, are quick to turn into refreshing pickles when you have more than you can eat fresh, and add cooling crunch to summer drinks and dips. Whatever you make, cucumbers are at their best within a day or two of cutting, when they are sweetest and crispest.
To store any you cannot use straight away, keep them in the salad drawer of the fridge in a loose plastic bag, where they will stay fresh for around a week. If the harvest really runs away with you, pickling is the time-honoured answer and lets you enjoy the taste of summer well into the colder months.
Cucumbers are one of the most rewarding crops you can grow, repaying a little warmth and water with weeks of crisp, refreshing fruit. For more seasonal growing inspiration, our greenhouse knowledge hub is full of guides, and if you have caught the bug you might enjoy our companion guides to growing tomatoes, courgettes and squash and chillies, all of which love the same warm, sheltered conditions as your cucumbers.