VegetablecucurbitSome care needed

Cucumber

Cucumis sativus

A crop where choosing the right type matters more than anything you do afterwards. Greenhouse cucumbers are productive and demanding, wanting warmth, humidity and constant moisture; ridge cucumbers are tougher, crop outdoors, and forgive a British summer. Sowing the wrong one for your setup is the usual reason cucumbers disappoint.

Position: Full sun
Water: high demand
Drainage: Moisture-retentive
Grows to: 180–200 cm × 45–90 cm
Hardiness: H1C
Harvest: July to September
Difficulty: Some care needed

Described view

A greenhouse cucumber trained up a string, showing tendrils, a large open leaf and a long straight fruit hanging from a leaf joint

August

Harvest

Cucumber’s year

Resolved for United Kingdom (general). Every window is stored against a climate event rather than a date, so a late frost pocket runs later than the band shows. What else August calls for.

Activity	M	M	J	A	S
Sow under cover	March.
Sow outdoors		May.
Plant out		May.
Harvest			July.	August.	September.

Names that cause confusion

cucumber — Two quite different growing types share the name. Greenhouse (all-female) cultivars need warmth and produce long smooth fruit; ridge cultivars are hardier, outdoor-grown and produce shorter rougher fruit.

Timing that travels

The band above resolves this plant's windows into months for one region. These are the windows themselves, stored against a climate event rather than a date — which is the form that survives being carried to a colder garden, a frost pocket, or next year.

Sow under cover
4–6 weeks before your last spring frost
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Cucumbers — sowing
Checked 2026-08-13
Sow outdoors
2–4 weeks after your last spring frost
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Ridge cucumbers
Checked 2026-08-13
Ridge cultivars only, into warm soil.
Plant out
1–4 weeks after your last spring frost
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Cucumbers — planting
Checked 2026-08-13

Conditions it needs

Light: Full sun
Direct sun: 6 hours a day or more
Frost: Frost tender
Hardiness rating: H1c (RHS)
Grows best at: 18–30 °C
Germinates at: 20–30 °C
Soil: Loam, Peat-free compost
Soil pH: 6–7
Drainage: Moisture-retentive
Water needs: high
Drought: poor tolerance
Waterlogging: poor tolerance
Heat: good tolerance
Wind and exposure: poor tolerance
Humidity: Greenhouse cultivars do best in humid air and dislike the dry conditions that suit tomatoes — which is why the two are an awkward pairing in one small greenhouse.

Where these figures come from

LightSourced guidancehigh confidence: Royal Horticultural Society: Grow your own: cucumbers
Checked 2026-08-13
Direct sunHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
FrostSourced guidancehigh confidence: Royal Horticultural Society: Cucumbers — hardiness
Checked 2026-08-13
Hardiness ratingSourced guidancehigh confidence: Royal Horticultural Society: RHS hardiness ratings
Checked 2026-08-13
Grows best atSourced guidancehigh confidence: Home and Garden Information Center — Clemson Cooperative Extension: Cucumber — culture
Checked 2026-08-13
Germinates atSourced guidancehigh confidence: OSU Extension Service — Oregon State University: Vegetable seed germination temperatures
Checked 2026-08-13
SoilHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Soil pHSourced guidancehigh confidence: University of Minnesota Extension — University of Minnesota: Soil pH for vegetable crops
Checked 2026-08-13
DrainageHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Water needsSourced guidancehigh confidence: Royal Horticultural Society: Cucumbers — watering
Checked 2026-08-13
DroughtHorticultural consensusmoderate confidence: Royal Horticultural Society: Cucumbers — watering
Checked 2026-08-13
WaterloggingHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
HeatHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Wind and exposureHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
HumidityHorticultural consensusmoderate confidence: Royal Horticultural Society: Cucumbers under glass
Checked 2026-08-13

On your soil

Computed by comparing this plant's recorded requirements against each soil's recorded characteristics. A recorded horticultural fact overrides the comparison where GrowingHQ holds one.

Soil	Verdict	Why
Heavy clay	Works, with one condition	Cucumber will crop on heavy clay, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. For a crop lifted before winter the risk is not rot but the season: waterlogged ground is cold and unworkable in spring, so sowing is late and germination patchy.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Sandy	Works, with one condition	Cucumber will crop on sandy, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Chalky and alkaline	Struggles here	Cucumber struggles on chalky and alkaline: The soil is substantially too alkaline for it: it wants pH 6 to 7, and this soil sits around 7.8 to 8.5. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering. A container or a raised bed of imported soil sidesteps the problem entirely.
Loam	Prefers this soil	Loam suits Cucumber as it stands: The pH suits it: it wants 6 to 7, and this soil is in that range. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Silty	Grows well here	Cucumber grows perfectly well on silty without special measures, though it is not the soil it would choose.
Peaty and acid	Works, with one condition	Cucumber will crop on peaty and acid, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. For a crop lifted before winter the risk is not rot but the season: waterlogged ground is cold and unworkable in spring, so sowing is late and germination patchy.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Shallow over rock	Works, with one condition	Cucumber will crop on shallow over rock, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Made ground and urban soil	Works, with one condition	Cucumber will crop on made ground and urban soil, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. For a crop lifted before winter the risk is not rot but the season: waterlogged ground is cold and unworkable in spring, so sowing is late and germination patchy.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.

Not sure which you have? Four hand tests will settle it.

Space and spacing

Mature height: 180–200 cm
Mature spread: 45–90 cm
Rooting depth: 40 cm
Spacing: 45–60 cm apart
Row spacing: 90 cm

Where these figures come from

Mature heightHorticultural consensusmoderate confidence

Cordon-trained greenhouse cultivars. Outdoor ridge types trail along the ground unless supported.

No external citation — see the evidence type above.

Checked 2026-08-13

Mature spreadHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Rooting depthHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

SpacingSourced guidancehigh confidence

Royal Horticultural Society: Cucumbers — spacing

Checked 2026-08-13

Row spacingHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Measured centre to centre. Plants set closer than this compete for light and water long before they look crowded, and the crowding cannot be undone once they are in.

In a container

Minimum volume: 20–30 litres
Minimum depth: 30 cm

Where the container figures come from

Minimum volumeSourced guidancehigh confidence: Royal Horticultural Society: Cucumbers in containers
Checked 2026-08-13
Minimum depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

Greenhouse types do well in large pots or growing bags with a cane or string to climb. They are heavy feeders and will yellow from the bottom up when the compost is exhausted.

Where and how you can grow it

Each way of growing is assessed separately, and “not assessed” is a real answer rather than a gap we have filled in with a guess.

Method	Suitability	What it needs
Greenhouse	Well suited source Sourced guidancehigh confidence Royal Horticultural Society: Cucumbers under glass Checked 2026-08-13	An all-female greenhouse cultivar; Vertical support; Humid air and steady moistureGreenhouse cucumbers want it warmer and more humid than tomatoes; sharing one small greenhouse between the two is always a compromise.
Polytunnel	Well suited source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	Vertical support
Hydroponics	Well suited source Sourced guidancehigh confidence Purdue Extension — Purdue University: Greenhouse cucumber production Checked 2026-08-13
Open ground	Workable Sourced guidanceDepends on conditionshigh confidence Applies when: Ridge cultivars only. Greenhouse cultivars grown outdoors crop poorly and are prone to bitterness. Royal Horticultural Society: Ridge cucumbers Checked 2026-08-13	A ridge or outdoor cultivar; A sheltered sunny site
Raised bed	Workable source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	A ridge cultivar; Support or room to trail
Container	Workable source Sourced guidancehigh confidence Royal Horticultural Society: Cucumbers in containers Checked 2026-08-13	20 litres or more; Support; Water at least daily in hot weather
Vertical growing	Workable source Horticultural consensusmoderate confidence A natural climber, so growing it upward suits it; the constraint is rooting volume rather than the habit. No external citation — see the evidence type above. Checked 2026-08-13	Netting or strings to climb
Aquaponics	Workable source Sourced guidancemoderate confidence Purdue Extension — Purdue University: Aquaponic fruiting crops Checked 2026-08-13
Windowsill	Marginal source Horticultural consensusmoderate confidence Royal Horticultural Society: Growing herbs and salads indoors Checked 2026-08-13

Growing it

TrainingTrain greenhouse cultivars up a string or cane, pinching out the growing tip when it reaches the roof and pinching side shoots two leaves beyond a developing fruit.
WateringKeep the compost consistently moist. Cucumbers wilt readily and irregular watering causes both bitterness and misshapen fruit.
PollinationAll-female greenhouse cultivars must NOT be pollinated: fertilised fruit turns bitter and swollen. Remove any male flowers that appear. Ridge cucumbers are the opposite and need insects to set.
FeedingFeed weekly with a balanced or high-potassium liquid feed once fruiting starts. Greenhouse cucumbers in containers exhaust their compost by midsummer and show it clearly — the oldest leaves yellow from the bottom of the plant upwards while the growing tip still looks well, which is a hunger sign rather than a disease.
ProtectionNot overwintered — both greenhouse and outdoor cucumbers are grown as annuals and are finished by the first cold nights, often before any actual frost. Outdoor plants suffer below about 10 °C and stop setting fruit. Clear the plants once they stop cropping rather than leaving them, and wash down a greenhouse afterwards: red spider mite overwinters in the structure and reinfests next year's crop from there.

Where this guidance comes from

TrainingSourced guidancehigh confidence: Royal Horticultural Society: Cucumbers — training
Checked 2026-08-13
WateringSourced guidancehigh confidence: Royal Horticultural Society: Cucumbers — watering
Checked 2026-08-13
PollinationSourced guidancehigh confidence: Royal Horticultural Society: Cucumbers — pollination
Checked 2026-08-13
FeedingHorticultural consensusmoderate confidence: Royal Horticultural Society: Cucumbers — feeding
Checked 2026-08-13
ProtectionSourced guidancehigh confidence: Royal Horticultural Society: Cucumbers — cultivation
Checked 2026-08-13

The bud you cut to becomes the new shoot, and it grows in the direction it points — which is why an outward-facing bud opens the plant up and an inward-facing one crosses the middle.

Is it worth putting under cover?

Whether it will grow there is on the methods table above. This is whether the space is well spent, which is a different question and usually the one being asked.

Structure	What protection is worth	What decides it
Greenhouse	Only possible under cover source GrowingHQ editorial positionmoderate confidence What protection is worth for this crop, judged against the same standard as every other record in this file. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13	Heat and humidity. The greenhouse cultivars are all-female and thin-skinned and are not outdoor plants at all; the ridge types that do grow outdoors are a different crop.Support to the roof; Shade in high summerWorth knowing which you have bought before planting. An all-female greenhouse cucumber outdoors is a disappointment with a long explanation behind it.
Polytunnel	Improves reliability source GrowingHQ editorial positionmoderate confidence What protection is worth for this crop, judged against the same standard as every other record in this file. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13	Humidity, which a tunnel supplies more readily than glass — cucumbers like it and their neighbours often do not. A tunnel is normally cropped in the ground, so soil-borne disease builds up under a rotation that never leaves cover. A greenhouse can sidestep it with pots or fresh growbags; a tunnel bed cannot.

On a windowsill

Does not work indoors

source

GrowingHQ editorial positionmoderate confidence

How long the crop is actually productive on an ordinary British windowsill without added light.

GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

Not a windowsill crop. The reason is given — usually light, root volume or sheer size. Size and humidity. Even a compact cucumber wants a metre of support and humid air, and it will get red spider mite in a dry heated room within weeks.

Growing it without soil

Nearly anything can be grown in a soilless system by somebody with enough equipment. The useful question is whether it is worth it, in which technique, and what goes wrong.

Well suited

An established soilless crop. Grown this way commercially or routinely by home growers, with predictable results.

source

Sourced guidancehigh confidence

Purdue Extension — Purdue University: Greenhouse cucumber production

Checked 2026-08-13

A standard protected soilless crop, with the same light and support demands as tomatoes.

Techniques that suit it

Drip-fed mediumSolution is dripped into an inert medium around each plant. The most forgiving technique and the one that suits large, long-season, heavy crops.
Ebb and flowA bed of inert medium floods and drains on a timer. The medium holds moisture between floods, which makes it far more tolerant of interruption than NFT.

source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Root space: Large, as for tomatoes — a long-season crop with a heavy water demand.
Support: Vertical strings or netting to two metres, tied in as the plant climbs.
source
Sourced guidancehigh confidence
Royal Horticultural Society: Cucumbers — training
Checked 2026-08-13
Lighting: Fully lit by lampsHorticultural consensusDepends on conditions
pH band: 5.5–6.5

Where these figures come from

Root spaceHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

LightingHorticultural consensusDepends on conditionsmoderate confidence

Applies when: Daylight under glass; lamps in a closed system, where the light demand is high.

No external citation — see the evidence type above.

Checked 2026-08-13

pH bandSourced guidancehigh confidence

Outside roughly this band, individual nutrients become unavailable even when they are present in the solution — which is why a crop can starve in a full reservoir.

Purdue Extension — Purdue University: Hydroponic solution management — pH

Checked 2026-08-13

What actually goes wrong

Accidental pollination of an all-female greenhouse cultivar, which makes the fruit bitter and swollen. Under cover the male flowers must be removed.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Cucumbers — pollination
Checked 2026-08-13
Warm solution. Above roughly 22 °C the water holds much less dissolved oxygen and root disease follows quickly, which is why summer is harder than winter in an indoor system.
source
Sourced guidancemoderate confidence
- Purdue Extension — Purdue University: Solution temperature and dissolved oxygen
Checked 2026-08-13
Pump or power failure. In nutrient film and aeroponics there is no reserve at the roots, so a crop can be lost within hours; medium-based systems hold moisture and are far more forgiving.
source
Sourced guidancehigh confidence
- Purdue Extension — Purdue University: Hydroponic system design — failure modes
Checked 2026-08-13

No nutrient recipes here

GrowingHQ records pH bands, which are measurable properties of nutrient availability, and deliberately records no EC or PPM targets and no mixing instructions. Published targets vary by cultivar, growth stage, water source and technique, and the figures that apply to your system are on the product you bought.

Harvesting

Time from sowing or planting: 9–12 weeks

source

Sourced guidancehigh confidence

Royal Horticultural Society: Cucumbers — timing

Checked 2026-08-13

When it is readyCut while the sides are still parallel and the skin is glossy. Fruit left to swell at the ends is past its best and slows the plant.
How to pick itCut the stalk with a knife or secateurs.

Where the harvest guidance comes from

When it is readyHorticultural consensusmoderate confidence: Royal Horticultural Society: Cucumbers — harvesting
Checked 2026-08-13
How to pick itHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

Keep picking

Regular picking keeps this plant producing. Fruit or leaves left to mature signal it to slow down or stop.

What goes wrong

Problem	How often	Notes
Powdery mildew	common source Sourced guidancehigh confidence Royal Horticultural Society: Powdery mildews Checked 2026-08-13
Slugs and snails	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	On young outdoor plants.
Aphids	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13

Start from what you can see

White powdery coating on leaves

Grown with, grown after, grown instead

Every relationship states its mechanism. A pairing nobody can explain is a pairing nobody has checked, and it does not go in.

Closely relatedCourgette
Both cucurbits sharing water demands, powdery mildew susceptibility and a dependence on correct handling of male and female flowers, so their calendars and problems run together.
source
Horticultural consensusmoderate confidence
Royal Horticultural Society: Cucurbits
Checked 2026-08-13

Safety and edibility

Preparation
Bitterness in cucumbers comes from cucurbitacins, produced under stress or when an all-female cultivar is accidentally pollinated. Strongly bitter fruit can cause stomach upset.
source
Horticultural consensusmoderate confidence
- Royal Horticultural Society: Bitter cucumbers
Checked 2026-08-13
Discard any fruit that tastes markedly bitter rather than trying to peel the bitterness away.

Sources for this page

GrowingHQ editorial synthesis · Home and Garden Information Center · OSU Extension Service · Purdue Extension · Royal Horticultural Society · University of Minnesota Extension

Each figure on this page carries its own citation, under the “where these figures come from” note in its section. Record last reviewed 2026-08-13.

If something is wrong with it

New growth twisted, puckered or distorted — 3 causes GrowingHQ holds for cucumber
White powdery coating on leaves — 2 causes GrowingHQ holds for cucumber
Plant wilting although the soil is moist — 4 causes GrowingHQ holds for cucumber
Lower leaves turning yellow — 2 causes GrowingHQ holds for cucumber

Something else? Work through it with the diagnostic tool.