How to grow cucumbers

Get the warmth right, keep the water consistent, and cucumbers will produce far more fruit than most growers expect — often faster than you can eat them.

Indoor vs outdoor: greenhouse and ridge cucumbers

The first decision when growing cucumbers is whether to grow them under cover or outside, because the right variety for each situation is quite different.

Greenhouse cucumbers (sometimes called indoor, frame, or English cucumbers) produce the long, smooth-skinned fruits familiar from supermarkets. They thrive in the warmth and humidity of a glass or polycarbonate greenhouse, and most varieties are bred to produce only female flowers — meaning the fruits develop without pollination and have no bitter seeds. They are not well suited to outdoor growing: cold draughts, wide temperature swings and rainfall on the foliage stress them quickly.

Ridge cucumbers are the outdoor type, named after the ridged or bumpy skin of many varieties. They're shorter and stubbier than greenhouse types, but just as tasty. They are hardier, more tolerant of variable conditions and their flowers need pollinating by insects to produce fruit, which happens naturally outdoors. In cool climates, grow ridge cucumbers in the sunniest, most sheltered spot available — against a south-facing wall (north-facing in the Southern Hemisphere) is ideal. Good outdoor varieties include 'Marketmore', 'Bush Pickle', 'La Diva' and many compact bush types suited to containers.

If you have a greenhouse, the long-fruited varieties give wonderful results. If you don't, choose a ridge variety and grow outside confidently — you don't need a greenhouse to have a generous cucumber harvest.

Sowing from seed and warmth requirements

Cucumbers are warm-season vegetables that absolutely need heat — both to germinate and to grow well. Seed germination is poor below about 18°C (65°F) and best between 20–25°C (68–77°F). Young plants will sit sulking rather than growing if the temperature drops to single figures, and a frost will kill them outright.

Timing sowing so plants are ready to go out after all frost risk has passed is essential. Because cucumbers grow quickly once conditions are right, sowing too early (so plants are sitting in pots on a windowsill for months) usually produces poorer results than a well-timed later sowing. A few weeks ahead of your expected last frost date is usually about right.

1. Sow seeds on their side. Fill a 9 cm pot with moist seed compost. Press one cucumber seed in on its side — this prevents the tip rotting in damp compost. Cover lightly and place in a propagator or on a heated mat at 20–25°C.
2. Move to bright light immediately after germination. Cucumber seeds typically germinate in 5–10 days. The moment seedlings emerge, move to a bright windowsill or greenhouse bench. Poor light makes them leggy and weak.
3. Pot on when the first true leaf develops. Move the seedling into a 12–15 cm pot of peat-free multipurpose compost. Always handle by a leaf, never the stem.
4. Harden off outdoor plants. About a week to ten days before planting outside, start placing pots outside during the day and bringing them in at night. This gradually acclimatises them to outdoor temperatures and prevents transplant shock.
5. Plant out after the last frost risk has passed. Space plants 45–60 cm apart if growing up a vertical support, or 75–90 cm apart if letting them sprawl. Plant into rich, well-prepared soil or a large container.

Supports and training to save space

Cucumbers are vigorous climbing plants with tendrils that will grip and scramble up almost anything. Growing them vertically is far more space-efficient than letting them sprawl across the ground, and it also improves airflow around the foliage — which reduces the risk of powdery mildew and other fungal problems.

• Canes and string: the simplest system for greenhouse growing is a vertical string from a high wire down to a ground anchor, with the plant trained up it. Tie the main stem loosely at intervals and let the plant wind its tendrils around the string.
• Trellis or netting: for outdoor ridge cucumbers, a panel of garden netting or a wooden trellis is ideal. Fix it to a fence or frame it with posts so it can take the weight of the plant and its fruits.
• Horizontal wire systems: in a greenhouse, horizontal wires fixed at 30 cm intervals up the side walls give tendrils plenty to grab and make it easy to train the plant up in a zigzag pattern, maximising space.
• Pinching out the growing tip: once a greenhouse cucumber has reached the top of its support, pinch out the growing tip to stop upward growth and encourage the plant to put energy into side shoots and fruit.

Even in a small raised bed or large pot, a simple teepee of bamboo canes allows three or four cucumber plants to grow upwards rather than outwards, making them a practical choice for compact gardens. See our guide to growing food in small spaces for more ideas on vertical cropping.

Soil, water and why consistency matters

Cucumbers are made up of more than 95% water, which tells you something important about how they grow: they need a consistent, generous supply of moisture throughout the entire growing season. Stress from inconsistent watering is the single most common cause of poor-quality, bitter or misshapen fruits.

• Soil: cucumbers are hungry, heavy-feeding plants that reward rich, free-draining soil with plenty of organic matter worked in. Dig in a generous amount of well-rotted compost or manure before planting. The soil should hold moisture without becoming waterlogged.
• Watering: aim for evenly moist soil at all times. In warm weather, pot-grown plants may need watering twice a day. Outdoor plants in the ground are more buffered, but still need regular watering during dry spells. Mulching around the base of outdoor plants with compost, straw or wood chip helps retain moisture and reduces how often you need to water.
• Watering technique: water at the base of the plant, directing water to the roots rather than over the foliage. Wet leaves in warm conditions encourage powdery mildew.

Feeding through the fruiting season

Cucumbers are among the most nutrient-hungry vegetables in the garden. They need a good supply of nitrogen in early growth to build strong foliage, and a shift towards potassium (potash) once they start producing fruit.

• Before flowering: a balanced liquid fertiliser or one higher in nitrogen encourages rapid leafy growth and a strong root system. Apply every one to two weeks.
• Once fruits are visible: switch to a high-potassium liquid feed — a tomato-type feed works well. Apply weekly throughout the fruiting period. Potassium promotes fruit development, improves flavour and helps the plant resist stress.
• Soil-grown plants: if you've prepared the soil well with compost before planting, plants in the ground need less supplemental feeding than container-grown cucumbers, which have a limited volume of compost to draw from.
• Greenhouse plants especially: restricted root runs in grow bags or pots mean nutrients are depleted quickly. Don't let feeding lapse mid-season.

All-female vs pollinating varieties

Understanding how your cucumber variety flowers is important, because it affects what you need to do — or avoid doing — to get a good harvest.

All-female (gynoecious) greenhouse varieties have been bred to produce only female flowers, which develop into fruit without any pollination. This is exactly what you want under glass: if male flowers were present and insects were to pollinate the female flowers, the resulting fruits would be bloated, filled with seeds, and bitter-tasting. Modern all-female greenhouse varieties (such as 'Bella', 'Flamingo', 'Passandra') have eliminated this problem. If you grow one of these, simply let it grow — no need to remove any flowers at all.

Outdoor ridge varieties produce both male and female flowers (you can tell them apart: female flowers have a tiny immature cucumber at the base, male flowers have a plain stem). They need pollinating by insects to set fruit. Outdoors this happens naturally. Do not remove flowers from outdoor types.

If you're unsure what type you have, check the seed packet. It will usually specify whether the variety is "all-female", "gynoecious" or suitable for outdoor growing. When in doubt, leave all flowers in place — removing male flowers from an outdoor type that needs pollinating will cost you fruit.

Harvesting regularly for a continuous crop

One of the most important things you can do for cucumber productivity is to harvest frequently. Cucumbers left on the plant to grow very large — especially to the point where they yellow and start to set seed — send a signal to the plant that its reproductive job is done, and fruit production slows or stops.

• Pick cucumbers when they are a good, usable size — for most varieties this is when they feel firm and are well-coloured, before the skin turns yellow or the fruit becomes puffy.
• For greenhouse types, this is usually when the fruit reaches the expected length for the variety. For ridge types, pick at 15–20 cm or when they feel solid and crisp.
• Use a knife or scissors to cut the fruit cleanly from the vine rather than pulling, which can damage the plant.
• Check plants every day or two during peak season — cucumbers grow faster than you might expect in warm weather, and a fruit you missed can double in size seemingly overnight.
• A single well-grown plant can produce many fruits over its season if kept picked. Let one go to seed and production across the whole plant drops markedly.

Powdery mildew and other common problems

Cucumbers are susceptible to a range of problems, but most can be managed or prevented with good cultural practice.

• Powdery mildew: the most common cucumber problem — a white, dusty coating on the leaves, caused by a fungal disease (Podosphaera xanthii). It's worst in warm, dry conditions with poor airflow. Improve ventilation, avoid wetting leaves when watering, and remove badly affected leaves promptly. Some varieties have bred-in resistance — look for the term on seed packets. The disease rarely kills the plant outright but weakens it and reduces yield.
• Bitter fruit: almost always caused by plant stress — erratic watering, temperature fluctuations, poor nutrition or very hot spells. Maintain consistent growing conditions and cut the bitter ends off affected fruits (the bitterness is concentrated near the stem end and skin).
• Failing to fruit (outdoor types): if outdoor plants flower but set no fruit, the flowers may not be getting pollinated. Encourage pollinators by avoiding pesticide use and growing flowers nearby. See our wildlife-friendly garden guide for more on supporting beneficial insects.
• Yellowing leaves: lower leaves naturally yellow as the plant matures. Widespread yellowing of upper leaves may indicate nutrient deficiency (particularly nitrogen or magnesium), overwatering, or root problems. Check your feeding regime and watering consistency.
• Slugs and snails: a threat mainly to young plants and seedlings. Protect newly planted cucumbers with physical barriers or biological controls. Our natural pest control guide has slug management covered.
• Red spider mite: a common greenhouse pest in hot, dry conditions, causing mottled, pale leaves and a fine webbing. Increase humidity by misting the floor and staging (not the plants), and improve ventilation. Biological control using predatory mites is highly effective in greenhouses.

Growing cucumbers in containers

Cucumbers can be grown very successfully in containers, making them a practical choice for patios, courtyards and small gardens. The keys to container success are size, water and feed.

• Container size: use the largest container you can manage — a minimum of 30–40 litres per plant. Cucumbers have vigorous root systems and a restricted root run causes the water and nutrient stress that leads to poor fruit quality.
• Compost: use a good-quality, peat-free multipurpose compost. Add a slow-release general fertiliser at planting time to top up what's in the bag.
• Watering: containers dry out far faster than open ground. In summer, check containers daily and water whenever the top few centimetres of compost feels dry. Self-watering containers or drip irrigation systems remove the guesswork.
• Support: even compact bush varieties benefit from a support. Use a short cane wigwam or lean canes against a wall or fence. Choose a bush or compact variety such as 'Bush Pickle', 'Spacemaster' or 'Patio Snacker' for smaller pots.
• Position: place containers in the warmest, sunniest spot you have. A wall that absorbs heat during the day and radiates it at night can extend your season noticeably.

Cucumber-growing checklist

• Choose the right type: greenhouse variety under cover, ridge variety for outdoor growing.
• Sow seeds on their side in warmth (20–25°C) a few weeks before your last frost date.
• Keep seedlings in bright light immediately after germination to prevent legginess.
• Install supports before planting to avoid root disturbance.
• Harden off plants thoroughly before moving outside.
• Keep soil consistently moist — never let it dry out completely.
• Switch to a high-potassium feed once fruits begin to form.
• Understand your variety: all-female types need no flower management; outdoor types need pollination.
• Harvest regularly — every day or two at peak season — to keep production going.
• Improve airflow and avoid wetting leaves to reduce powdery mildew risk.