Cucumber
Cucumis sativus
Cucumbers come in two types for UK growers: greenhouse (smooth-skinned, longer) and outdoor/ridge (shorter, sometimes spiny). Outdoor varieties like 'Marketmore' and 'Crystal Lemon' are tough enough for UK summers and produce heavily from July to September. Greenhouse varieties give earlier, more prolific crops but need consistent warmth and humidity. All cucumbers are tender — don't plant out until early June in most of the UK. They love to climb, and training them up strings or trellis saves space and keeps fruits clean and straight. Water consistently; erratic watering causes bitter-tasting fruits. Feed weekly with tomato fertiliser once fruits start forming. For greenhouse types, remove male flowers to prevent pollination, which makes fruits bitter and seedy. Outdoor types need pollination, so leave the bees to do their work.
Plan where to grow Cucumber using our vegetable garden planner.
When to Sow Cucumber
Sow cucumber in April, May, June.
Time to Harvest Cucumber
Expect to harvest approximately 3 months after sowing, usually from July to September.
Companion Plants for Cucumber
- Garden Pea
Early peas are finished by midsummer, just as outdoor cucumbers need the room, and they leave nitrogen behind in the soil.
- Sunflower
Outdoor cucumbers can scramble up sturdy sunflower stems, and the flowers attract bees to help pollination of ridge types.
- Sugar Snap Pea
Sugar snap peas crop early and can share supports with outdoor cucumbers, handing over the space as the cucumbers take off.
Expected Yield
Outdoor plants give 10–20 fruits; greenhouse plants can give 20–50.
Growing Tips
Can be grown vertically to save space
Pruning Cucumber
On greenhouse cordons, pinch out side shoots two leaves beyond a fruit and stop the main stem when it reaches the top of its support; remove male flowers from all-female varieties.
Common Problems with Cucumber
Powdery mildew
A white powdery coating on leaves that's almost inevitable by late summer. Keep plants consistently watered (dry roots make the plant more susceptible), ensure good ventilation in greenhouses, and remove the worst-affected older leaves to slow the spread. Resistant varieties and regular feeding help plants outgrow the damage.
Bitter fruit
Bitter-tasting cucumbers are caused by a compound called cucurbitacin, which builds up when plants are stressed by irregular watering, wide temperature swings, or dry conditions. Water deeply and consistently, maintain even temperatures under cover, and remove male flowers on greenhouse varieties to prevent pollination, which also causes bitterness and seedy fruit.
Whitefly
Tiny white flies cluster on leaf undersides, sucking sap and excreting sticky honeydew that attracts sooty mould. Hang yellow sticky traps at plant height to monitor and reduce numbers. For biological control, introduce the parasitic wasp Encarsia formosa — it's highly effective under cover. Good ventilation and avoiding overcrowded planting reduce the humidity whitefly thrives in.
Cucumber: common questions
When should I sow cucumber in the UK?
Sow cucumber from April to June. Sow under cover (a greenhouse, windowsill or heated propagator) and plant out once the weather has warmed.
How far apart should I plant cucumber?
Space cucumber about 60cm apart. It grows to around 2m tall. Sow seeds 1–2cm deep.
How long does cucumber take to germinate?
Cucumber seeds usually germinate in 3–5 days (in warmth), depending on temperature.
When is cucumber ready to harvest?
In the UK, cucumber is usually harvested from July to September. It's ready about 3 months after sowing.
Does cucumber come back every year?
No. Cucumber is an annual: it grows, flowers and dies in one year, so sow it again each year. Some annuals self-seed if a few flowers are left to set seed.
When should I prune cucumber?
On greenhouse cordons, pinch out side shoots two leaves beyond a fruit and stop the main stem when it reaches the top of its support; remove male flowers from all-female varieties.
What grows well with cucumber?
Good companions for cucumber include Garden Pea, Sunflower and Sugar Snap Pea. See the companion plants section above for why each one helps.
Is cucumber frost hardy?
No. Cucumber is tender and is damaged by frost, so keep it under cover until all risk of frost has passed and bring it in, or grow it under glass, when nights turn cold.
What crop rotation group is cucumber in?
Cucumber belongs in the cucurbits group for crop rotation. Grow it in a different bed each year, alongside other cucurbits, so pests and diseases don't build up in the soil.
Cucumber guides
Plan your cucumber in the allotment planner
Drag and drop plants onto your plot and get personalised sowing reminders.
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