how to plant, grow & care for cucumbers
complete growing guide
The best cucumbers seem to be those that come in odd shapes and sizes. I love varieties like ‘La Diva’, whose fruits are best when they are the size of a large cigar – perfect for crudités or dipping into smoked mackerel pâté.
‘Crystal Lemon’ is also unusual, growing round instead of long and with a lovely sweet taste and excellent crunchy flesh. There’s also the more classical ‘Burpless Tasty Green’, which has excellent texture and fabulous flavour and grows to a more familiar 20cm (8in) long.
These are all very easy to grow, suitable for the outdoors or undercover and absolutely delicious and very prolific – you only need a few seeds to end up with a glut of cucumber fruit.
Browse our range of cucumber seeds and seedlings or take a look at our small cucumber plants, which are ready to plant out in your vegetable garden.
- Common name Cucumber
- Latin name Cucumis sativus
- Type Half-hardy annual
- Height 2m (6½ft)
- TLC rating Easy
- Aspect Full Sun
- Spacing 30cm (1ft)
- Yield 4 month harvest, up to 30 fruits per plant
- Suitable for pots Yes
- Grow in a greenhouse Yes
how to grow cucumbers
where to grow cucumbers
Soil type: Cucumbers thrive in moist, fertile soil. Dig in a good lot of compost or well-rotted manure when planting out seedlings, which will enrich the soil and help retain moisture.
Aspect & Position: Cucumber plants need a spot in full sun, preferably in a sheltered position with support from a trellis or canes.
when to plant cucumbers
Sow undercover in March or April, and plant out in late May and June.
how to plant cucumbers
sowing cucumber seeds
Seeds should be sown undercover in a greenhouse or somewhere warm in March or April.
Sow them individually, on their edge rather than flat (this is to prevent rotting) into 7.5cm (3in) pots filled with peat-free compost. Sow them about 2cm (¾in) deep.
They will germinate best at high temperatures of at least 21ºC (70ºF). Seedlings should appear in just over a week and quite quickly the pot will fill with roots. If it’s too soon to plant out, pot them on into larger pots.
planting cucumber seedlings & plants
Once the frosts are over, harden off your cucumber plants. Do this by leaving the seedlings outside during the day in a bright, sunny spot and bringing them back in, or covering with horticultural fleece, in the evening. They can be planted out in late May or June when the weather has warmed. They can also be planted in the greenhouse earlier than this.
Space the young plants at least 30cm (1ft) apart. And dig lots of compost or well-rotted manure into each planting hole as they are hungry plants. Water in well on planting.
how to care for cucumbers
The soil should be kept moist but don't over water. Water in the morning to make sure the base of the stem is dry before the temperature drops at night, as the stem can be prone to rot.
Once the plants are growing well and planted out, give them a balanced feed, such as GroChar. Don't use a high-potash tomato feed, as it will slow growth and make the cucumbers bitter.
Make sure you give your cucumber plants early support soon after planting or they will get a kink in the stem which may cause them to collapse later.
Cucumbers can reach great heights given the opportunity – left to their own devices they will sprawl, so if you don’t give them any support, ensure there is plenty of space around them.
If you are planting a row of plants, you can create a netting frame over which they can all climb. If you have just one or two plants, use a triangle of canes at 1½m (5ft) to support each plant or give them a trellis to climb.
growing in a greenhouse
The cucumbers we grow are all happy outside. I find growing them in a greenhouse takes a lot of work. There’s the training and the daily watering, but they also tend to draw whitefly to my greenhouse tomatoes – so I like to keep my cucumbers and my tomatoes separate, which is another reason I prefer my cucumbers outside. Greenhouse-grown cucumbers give higher yields, however.
Once the plants have reached a good height, pinch out the growing tips to encourage more fruits on bushy growth.
Keep picking the young fruit when they are green, with no signs of yellowing. Once the lower fruits are harvested, more will form higher on the plant.
- Sow cucumber seeds undercover in March or April.
- In May, harden off the seedlings or young plants.
- Plant out when the risk of frost has passed.
- Water the plants well, particularly during a drought.
- Some cucumber plants will produce fruits from late June into October, so continue to harvest.
- Use horticultural fleece to protect plants from early frosts.
- Plan which cucumbers you’d like to sow and grow in spring.
pests, diseases & common issues
Powdery mildew can be a problem during hot, dry spells. It’s a fungal disease that shows up as a powdery white coating on the foliage.
Keep the soil moist and avoid getting leaves wet while watering. Ensure good air circulation around the plant and make sure it doesn’t suffer stress through over or under watering.
Once it really heats up, give the plants a weekly dousing with chive or comfrey tea, which is a brilliant organic anti-fungus treatment made from rotted-down chive or comfrey leaves. Liberally sprinkle them over the plants and that will really keep mildew at bay for another two or three weeks before the end of the season.
Verticillium wilt is relatively uncommon, but the fungal disease can affect cucumbers, infecting the plants from the roots. Signs include wilting leaves, yellowing leaves and a dieback. The fungal disease lives in the soil, so you need to remove the plant with any soil attached to the roots and dispose of it.
These small white pests can be a particular issue for greenhouse-grown cucumbers. You’ll be able to see them on the leaves and they suck the sap of the plant. A healthy plant that isn’t under stress (from over or under watering, for example) should be able to withstand the attack. There are sticky sheets that can attract whitefly and these can be installed around your pots, but they trap good insects too. Basil and marigolds also make great companion plants, either deterring or luring away whitefly and aphids. And you can try Whitefly Control Encarsia that can be hung around the plants.
cucumber mosaic virus
If you notice yellow mottling on the leaves and stunted growth, the symptoms could indicate cucumber mosaic virus. The cucumbers might also be bitter to taste with puckered spots on the skin. It is most commonly passed on to the plant by aphids, so keep an eye out for these and remove them from the plant as soon as you see them. Clean any tools you’ve used around the plant to avoid transmitting the virus to other plants in the garden.
what are the problems when growing cucumbers in a greenhouse?
Whitefly can be a problem for glasshouse-grown cucumbers. It’s also important to keep on top of watering, daily at the height of summer, to ensure they thrive. But greenhouse-grown cucumbers give higher yields than those grown outdoors, so the efforts can be worth it.
why are my cucumber leaves turning yellow?
A likely cause is over watering. Ensure they are watered and fed regularly to avoid a nutrient deficit. Alternatively, it could be a symptom of cucumber mosaic virus.
Why are my cucumbers turning yellow?
Overripe cucumbers begin to turn yellow. Harvest them young when they are still completely green.
why are my cucumber plants wilting?
Wilting can be a sign of a stressed cucumber plant that is being over or under watered. Cold temperatures can also lead to wilt. The worst case scenario is verticillium wilt.
why are my cucumber plants turning brown?
Browning leaves can be the eventual result of any of the pests, fungal diseases or viruses that can affect cucumber plants. Try to identify the problem and resolve it if possible, and remove any affected leaves.
frequently asked questions
how many cucumbers can you harvest per plant?
Depending on the variety, you can expect to harvest around 20 cucumbers per plant.
how tall do cucumber plants grow?
Cucumber plants can easily reach 2m (6½ft) and they prefer to have a support to climb up.
how long do cucumbers take to grow?
Seeds sown in early spring can give you fruits as early as late June.
how long do cucumber seeds take to germinate?
Cucumber seeds can germinate within a week if given warm conditions above 21ºC (70F).
how do you prune cucumbers?
If your cucumber plant has reached the desired height, pinch off the growing tips to encourage bushiness and more fruit.
how deep should you plant cucumbers?
Sow cucumber seeds vertically rather than flat about 2cm (¾in) deep.
should you remove dead leaves from my cucumber plant?
Yes, you can remove any dead leaves from the plant.
do cucumbers grow back every year?
No, cucumbers are half-hardy annuals, which means you need to plant fresh seed each year.