Overview
What cucumbers need, when they crop, and whether they suit your space.
A healthy cucumber plant can outpace the kitchen: fruits grow so fast that one missed day turns a crisp pickler into a yellow, seedy club, and an old fruit left on the vine slows the whole plant. Start them late in warmth, give them something to climb, keep the water steady, and pick every two or three days.
Quick facts
- Botanical name
- Cucumis sativus
- Soil pH
- 6.0 – 6.5
- Feeding
- Moderate feeder
- Temperature
- 24 – 29 °C
- Hardiness
- Any zone, as an annual
- Time to harvest
- 50 – 70 days
- Propagation
- Seed
Optimal growth
Keep above 12 °C
Growing details
- Spacing
- 30 cm (12 in)
- Sowing depth
- 20 mm (¾ in)
- Frost sensitivity
- Frost tender
Growing calendar
- Start indoors: February, March, April
- Sow outdoors: May, June, July
- Transplant: May, June
- Harvest: July, August, September, October
Heated greenhouse mid-Feb to mid-Mar; unheated greenhouse in April; outdoor plants late April. Once the soil has warmed and frost has passed; a second US sowing around 1 July. Greenhouse from late May, outdoors from early June, once it stays above 12 °C (54 °F). Outdoors to September; in a warm greenhouse into October.
Is this plant right for you?
- Heavy cropper
- Needs warmth
- Climbs a support
- Greenhouse or outdoors
- Good in pots
- Thirsty
- Frost tender
Good to know
Plan for support early: this plant needs a stake, cage or frame once it gets going. Keep it above 12 °C (54 °F): frost kills it.
Before You Grow
Choose a greenhouse or outdoor type, and the warmest, sunniest spot with rich soil.
Never grow ridge cucumbers beside all-female greenhouse types: pollinated, the greenhouse fruits turn bitter.
What you need
Seed or young plants
A greenhouse or outdoor variety. See choose your cucumbers.
10 cm (4 in) pots and warmth
Seeds need at least 20 °C (68 °F). See sowing.
A warm, sunny spot
A greenhouse, or a sheltered bed outside. See where they grow best.
Compost or manure
Two bucketfuls per plant. See soil.
Supports
Strings, canes, netting or trellis. See training.
High-potash liquid feed
For plants in pots and growing bags. See feeding.
Choose your cucumbers
Pick first by where you will grow them, then by what you want to do with the fruit.
Greenhouse cucumbers need warmth and give long, smooth fruits like supermarket ones. Most modern varieties are all-female: they set fruit without pollination, and must not be pollinated or the fruit turns bitter and seedy. ‘Bella’ and ‘Mini Munch’ are examples.
Outdoor or ridge cucumbers tolerate cooler conditions and give shorter fruits, often with rough, ridged skin. They need insects to pollinate them. Some varieties, such as ‘Swing’ and ‘La Diva’, grow inside or out.
Slicing or pickling. Slicers are long, smooth and eaten fresh; picklers are short and blocky with bumpy skin, picked small. ‘Burpless’ varieties are mild with tender skin.
Bush varieties are compact, for small gardens and pots.
Disease resistance is worth seeking out: many varieties resist powdery mildew or cucumber mosaic virus.
Cucumber types compared
-
Greenhouse, all-female
- Fruit
- Long, smooth
- Pick at
- 20 to 25 cm (8 to 10 in)
- Pollination
- None; remove any male flowers
- Grow
- Greenhouse or polytunnel
-
Mini
- Fruit
- Small, smooth
- Pick at
- About 8 cm (3 in)
- Pollination
- Check the packet
- Grow
- Greenhouse or warm spot
-
Outdoor (ridge) slicing
- Fruit
- Shorter, often rough
- Pick at
- 15 to 20 cm (6 to 8 in)
- Pollination
- Bees
- Grow
- Warm, sheltered outdoors
-
Pickling
- Fruit
- Short, blocky, bumpy
- Pick at
- 5 to 10 cm (2 to 4 in)
- Pollination
- Bees
- Grow
- Outdoors
-
Burpless
- Fruit
- Long, slender, mild
- Pick at
- As slicers
- Pollination
- Varies
- Grow
- Outdoors or under cover
Sizes from the RHS, Iowa State and Illinois. With a greenhouse, an all-female variety; without one, an outdoor slicer or a pickler.
Where cucumbers grow best
Cucumbers are tender, warm-season plants. They crop well in a greenhouse or polytunnel, or outdoors in a warm, sunny, sheltered spot.
Temperature. They grow best at 24 to 29 °C (75 to 85 °F) (Clemson); for greenhouse plants the RHS aims for 18 to 25 °C (64 to 77 °F) and shades the glass in hot spells. A light frost kills them.
Warm nights. Plant out only once temperatures stay above 12 °C (54 °F) (RHS).
Humidity. Greenhouse cucumbers like moist air: damp down the floor in hot weather, which also deters red spider mite and mildew.
Sun and shelter. Full sun, at least six hours a day. Wind whipping the vines makes vertical training hard outdoors (Illinois), so choose shelter.
Space. Trailing vines spread far. Training them up a support saves room and keeps fruit clean.
- Best growth
- 24 to 29 °C (75 to 85 °F)
- Plant out above
- 12 °C (54 °F)
- Sun
- At least six hours a day
Soil
Cucumbers want fertile, well-drained soil, rich in organic matter, that holds moisture.
Preparation. Dig two bucketfuls of garden compost or well-rotted manure into each planting site a few weeks before planting, so the soil settles (RHS). Clemson aims for up to 20% organic matter.
pH. 6.0 to 6.5 (Clemson).
Drainage. A slightly raised bed helps drainage and some diseases.
Warm it up. Black plastic mulch or a cloche warms the soil for early crops (Illinois, Clemson). Seeds won’t germinate in soil below 10 °C (50 °F).
Planting
Sow in warmth, handle the roots gently, and plant out only once nights are warm.
Cucumbers hate root disturbance: sow in individual pots and plant out without breaking the rootball.
When to sow and plant cucumbers
Sowing time depends on where the plants will grow. They are ready to plant out about a month after sowing, so there is no gain in starting early without heat.
Heated greenhouse. Sow mid-February to mid-March and plant from late March (RHS).
Unheated greenhouse or polytunnel. Sow in April; plant from late May, once it stays above 12 °C (54 °F) inside.
Outdoors. Sow indoors in late April and plant out from early June. Or sow directly outside in late May or June under a cloche or fleece.
In the US, sow direct or plant out after the last frost once the soil reaches 16 to 21 °C (60 to 70 °F) (Iowa State); Clemson waits for 21 °C (70 °F). UMD sows a second crop around 1 July.
- Plant out about a month after sowing.
- Outdoors only once nights stay above 12 °C (54 °F).
- A second US sowing around 1 July.
How to sow cucumbers
One seed to a pot, in warmth, so each plant moves without root disturbance.
-
Fill small pots
10 cm (4 in) pots of peat-free seed compost, watered well. Peat or paper pots can go straight into the ground (Iowa State).
-
Sow one seed on its side
1 to 2 cm (½ to ¾ in) deep, on its edge rather than flat (RHS, Gardeners’ World).
-
Keep them warm
At 21 °C (70 °F) in a propagator, or in a clear bag on a warm windowsill. Below 20 °C (68 °F) germination is poor.
-
Grow on in light
Once up, remove the cover and keep them warm, bright and watered, with a short cane to keep them upright.
-
Don’t let them get too big
Plant out at two to four true leaves. Oversized plants in pots transplant badly (Illinois).
How to plant cucumbers
Gently, into warm, rich soil, with the support already in place.
-
Harden off outdoor plants
Over at least a week, gradually getting them used to outdoor conditions.
-
Water first
Water well before planting and keep the rootball whole: cucumbers don’t transplant as bare roots.
-
Space them out
Trained up supports, 30 to 45 cm (12 to 18 in) apart; left to sprawl, 90 cm (3 ft). Two plants to a standard growing bag.
-
Put in supports now
A string or cane in the greenhouse; a cane wigwam, netting or trellis outdoors.
-
Firm gently and water
Then protect from slugs, and cover outdoor plants with fleece or a cloche until they are growing strongly.
Care
Steady water, feeding in pots, training up a support, and knowing which flowers to keep.
Uneven watering and heat stress make fruit bitter. Mulch and water steadily at the base.
Care by growth stage
Young plants
Water: keep evenly moist · Protect: slugs, cold, beetles
Tie in to supports and protect from slugs. See training.
Climbing
Mulch: once soil is warm
Pinch out tips and side shoots as they grow. See training.
Flowering
Feed: pots every 10 to 14 days · Humidity: damp down
Start high-potash feeding; remove male flowers on all-female types. See flowers.
Fruiting
Water: most critical now
Pick every two to three days and water more. See harvesting.
End of season
Clear: plants and trash
Clear plants and debris, which shelter beetles and disease, and rotate next year.
Watering cucumbers
Cucumbers have shallow roots and need ample moisture at every stage, most of all while fruits set and swell.
How much. Water deeply, so the soil is moist at least 15 cm (6 in) down (Clemson). Outdoors in dry weather, a good soak once a week (Iowa State); water more often once fruits form (UMD).
Pots and greenhouse. Keep the compost evenly moist; in hot spells pots may need water daily (RHS).
How. At the base, in the morning, keeping the leaves dry against mildew. A pot sunk beside each plant takes water straight to the roots and keeps the stem from rotting (RHS).
Mulch with compost, straw or bark to hold moisture and keep fruit clean, leaving a gap round the stem.
Feeding cucumbers
In the ground, compost or manure dug in before planting is usually enough; plants in rich soil shouldn’t need feeding (RHS). Without a soil test, Iowa State works in a general fertiliser before planting.
Side-dressing. US extensions add nitrogen when vines start to run (Illinois), or a week after flowering starts and again three weeks later (UMD).
In pots and growing bags, feed every 10 to 14 days with a general liquid feed, then switch to a high-potash feed such as tomato feed once flowering starts (RHS).
Misshapen fruit can mean low fertility as well as poor pollination (Illinois).
Training and pinching out
Trained up a support, cucumbers take little ground, stay cleaner, suffer less disease and are quicker to pick. Pinching out keeps their energy in fruit rather than vine.
Greenhouse cucumbers. Train the main stem up a cane or a string tied to the roof. Pinch out the tip when it reaches the roof. Pinch each side shoot two leaves beyond a female flower, and flowerless side shoots at 60 cm (2 ft) long (RHS).
Outdoor cucumbers. Pinch out the growing tip at seven leaves to encourage side shoots, and pinch flowerless side shoots after seven leaves. Train the side shoots up netting, a wigwam or trellis, or let them trail.
Trailing plants. Lay a weed-suppressing membrane or organic mulch under the vines to keep fruit clean and off wet soil.
Tie in gently. Stems need tying at first; tendrils then cling on their own. Supported long varieties hang free and grow straighter.
Flowers and fruit set
Cucumbers carry separate male and female flowers. A female flower has a tiny cucumber behind it; a male flower sits on a plain stalk.
Standard (outdoor) types need bees to carry pollen from male to female flowers: 8 to 12 bee visits per flower (UMD). The first 10 to 20 flowers are usually male, so early flowers dropping without fruit is normal. Keep the male flowers.
All-female greenhouse types set fruit without pollination. Remove any male flowers that appear: pollinated fruit is bitter and seedy (RHS).
Gynoecious hybrids make mostly female flowers and crop early and heavily; the packet includes a few seeds of a standard variety as a pollinator.
Poor set comes from too few bees, cool wet weather, or insecticides that keep bees away. Plant flowers nearby for pollinators, and spray, if at all, early or late in the day.
Cucumbers in containers
Cucumbers crop well in pots and growing bags, on a patio or in a greenhouse.
Size. A pot at least 30 cm (1 ft) wide and deep, one plant to a pot, or two plants to a standard growing bag (RHS). Use peat-free multi-purpose compost.
Variety. Bush and mini varieties suit pots best.
Care. Add a support at planting. Water to keep the compost evenly moist, daily in hot spells, and feed every 10 to 14 days, with high-potash feed once flowering starts.
Problems
Bitter or misshapen fruit, beetles, mildew and viruses are the usual troubles.
Common cucumber problems
Most fruit problems come down to water, heat or pollination.
Bitter fruit
- Stress
- Pollination
Hot, dry stress or big temperature swings push bitter cucurbitacins into the fruit, mostly at the stem end and under the skin. On all-female types, pollination is the cause. Water steadily, remove male flowers under glass, and choose less-bitter varieties such as ‘Marketmore 76’ or ‘Diva’.
Flowers but no fruit
- Pollination
- Early flowers
The first flowers are male and drop off. Later, too few bees, cool wet weather or insecticides reduce set. See flowers and fruit set.
Curled or narrow-ended fruit
- Pollination
- Fertility
Poor pollination or low fertility. Remove them; a side-dressing can help later fruit (Illinois).
Plant stops producing
- Overmature fruit
An old, yellow cucumber left on the vine slows or stops new fruit. Pick everything at the right size.
Plants wilting and dying
- Bacterial wilt
- Beetles
Often bacterial wilt, spread by cucumber beetles. See diseases.
Stem rotting at soil level
- Wet neck
Water sitting around the stem. Water into a sunk pot beside the plant and keep mulch away from the stem.
More problems with cucumbers
Common pests
Cucumber beetles
In North America, yellow-and-black striped or spotted beetles about 6 mm (¼ in) long. They attack seedlings and spread bacterial wilt. Cover young plants with row cover until flowering and control them from emergence.
Glasshouse red spider mite
Mottled, rusty leaves and fine webbing in hot, dry greenhouses. Raise humidity; biological controls are available.
Glasshouse whitefly
Tiny white insects under leaves; their honeydew grows black sooty mould.
Slugs and snails
Eat seedlings and young plants, and fruit lying on the ground. Training plants upward helps.
Common diseases
Powdery mildew
White powdery patches that shrivel the leaves, worst in late summer and in dry greenhouses. Water at the base, keep plants moist, raise humidity under glass, and grow resistant varieties.
Cucumber mosaic virus
Yellow mosaic mottling, stunted plants and blotchy, bitter fruit. Spread by aphids; there is no cure. Destroy affected plants and grow resistant varieties.
Bacterial wilt
Leaves turn dull, then whole vines wilt and die, often scattered through the patch. Spread by cucumber beetles; control the beetles early and remove affected plants.
Downy mildew and anthracnose
Leaf spots in warm, wet weather, often later in the season. Water at the base, avoid handling wet plants, and clear debris.
Harvest & Use
Pick small and often, cutting rather than pulling.
Harvesting cucumbers
Most varieties crop in 50 to 70 days, depending on variety (Clemson); UMD gives 50 to 65 days from seed, and Gardeners’ World about 12 weeks from sowing.
Size. Picklers at 5 to 10 cm (2 to 4 in); slicers at 15 to 20 cm (6 to 8 in); mini cucumbers at about 8 cm (3 in); long greenhouse types at 20 to 25 cm (8 to 10 in).
Ready means uniformly green, firm and crisp, before the skin yellows or the seeds harden.
Pick often. Every two to three days: fruit grows fast, and overmature cucumbers left on the vine stop new ones forming.
How. Cut the stalk with a knife or secateurs, early in the morning while cool. Don’t work among wet plants: it spreads disease.
- Every 2 to 3 days.
- Firm, green, before seeds harden.
- Cut, don’t pull.
Storing and using cucumbers
Cucumbers are best eaten fresh, soon after picking.
In the fridge. Cool them straight after picking and keep them in a loose or perforated bag. Illinois gives up to three days; at 10 to 13 °C (50 to 55 °F) and high humidity they last 10 to 14 days (Iowa State).
Pickling. Small fruits pickle whole as gherkins, or slice larger ones.
Bitter ends. Cut off the stem end and peel: the bitterness sits there and under the skin.
More to Explore
Quick answers, guides that pair well with cucumbers, and the sources behind this one.
Frequently asked questions
Why are my cucumbers bitter?
Heat and dry stress, or pollinated all-female fruit. Cut off the stem end and peel. See common problems.
Why are my cucumber flowers falling off?
The first flowers are male and drop naturally. Female flowers have a tiny fruit behind them.
Should I remove male flowers?
Only on all-female greenhouse varieties. Outdoor types need them for pollination.
Do cucumbers need a trellis?
No, but training them up saves space and keeps fruit clean. See training.
How often should I water cucumbers?
Keep the soil evenly moist: a deep weekly soak outdoors in dry weather, often daily for pots in hot spells.
When should I pick cucumbers?
Every two to three days, at the size for the variety, while firm and green.
Can I grow cucumbers in pots?
Yes: one plant in a pot at least 30 cm (1 ft) wide and deep, or two to a growing bag.
Will cucumbers cross with melons or squash?
No. Cucumbers only cross with other cucumbers, and that doesn’t change this year’s fruit, except for parthenocarpic (seedless, all-female) types, which fruit without pollination and turn bitter if pollinated.
Why are my cucumbers misshapen?
Poor pollination or low fertility. Remove them, help pollination, and feed only if growth is weak. See common problems.
Related guides
Sources
- How to grow cucumbers (opens in a new tab) Royal Horticultural Society
- Growing cucumbers in the home garden (opens in a new tab) Iowa State University Extension and Outreach
- Growing cucumbers in a home garden (opens in a new tab) University of Maryland Extension
- Cucumber (opens in a new tab) University of Illinois Extension
- Cucumber (opens in a new tab) Clemson Cooperative Extension
- How to grow cucumbers (opens in a new tab) BBC Gardeners’ World