how to grow cucumbers

How to Grow Cucumbers [Outdoors & in Greenhouses]

Homegrown cucumbers are fabulous and it’s relatively easy to grow cucumbers from seed.    The most important thing to know about growing cucumbers is that there are two main types of cucumbers.  Some can be grown outside and some cucumbers can be grown in a greenhouse.  You’ll need to treat these two different types of cucumbers, well, differently.  So in this guide on how to grow cucumbers, we’ll cover the two types of cucumbers, how to grow cucumbers in a greenhouse and how to grow cucumbers outside.    You don’t need heaps of space to grow cucumbers, you can grow cucumbers in pots and containers and you can grow cucumbers in bags or directly in the ground.

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How to Grow Cucumbers

The first thing you need to decide when growing cucumbers in the UK is to decide where you’re going to grow them.  Will you grow cucumbers outdoors?  Or grow cucumbers in a greenhouse?

  • Greenhouse cucumbers have long, smooth fruits.
  • Outdoor cucumbers are called ridge cucumbers and they tend to be shorter, have rougher skin and they’re a bit fatter.

You can sow seeds for both outdoor cucumbers and greenhouse cucumbers inside and you can also buy young plants.  If you want to get started quickly growing cucumbers, then buying a small potted cucumber plant is your best option.

Sowing Cucumber Seeds

You can grow cucumbers from seeds, but when you sow the seeds will depend on where you are planting and growing your cucumbers.  If you have a heated greenhouse you can sow cucumber seeds as early as February.  If your greenhouse is unheated, or you have an unheated propagator, then you’ll want to wait until the middle or end of March to plant them.  If you’re planting cucumber seeds outside without any cover, then you’ll want to wait until May to plant the cucumber seeds.

Plant cucumber seeds to a depth of 1 centimetre and keep them at a temperature of about 20 degrees Celsius for about 10 days.  You can do this more easily if you’ve planted the seeds in small pots (make them about 7.5 centimetres and ensure they have good drainage), and then you can put the pots in either the greenhouse or inside a propagator or even inside a plastic bag.

growing cucumbers seeds

When the cucumber seeds have germinated keep them warm – I tend to use a sunny windowsill that is draft-free.  If it gets below 15 degrees, then the baby plants are going to suffer.  Keep the cucumber plants in moist but not soggy compost.  The old adage of water little but often is a good one with cucumbers.   Cucumbers are 96% water, so bear that in mind while they’re growing!  You should also take care if the sun becomes strong as small plants can get scorched by direct sunlight.  When the plants are big enough to transplant take care of the roots, as they are EXTREMELY delicate.

Best Varieties of Cucumbers to Grow in the UK

Here are the varieties of cucumbers that grow best in the UK.

Here are alternative cucumber seeds that do well in the UK.

Two Main Types of Cucumbers

As I’ve mentioned there are two types of cucumbers, those that you grow inside a greenhouse and those you grow outside.  Let’s now cover the details of growing both types of cucumbers in the UK.

Growing Cucumbers Outside

While the general rules of watering, feeding and pinching out are the same for growing outdoor and greenhouse cucumbers there are a few differences.  So here’s how to grow outdoor cucumbers.

When to plant cucumbers outside

If you’re planting cucumbers outside, then you’ll want to wait until all signs of frost has completely gone.  Start your seeds off inside in pots and acclimatise your baby cucumber plants over about 10 days.  It’s best to start with a few hours a day, always bringing them in at night.  You can gradually increase the time that you leave them outside.

Cucumber plant ready to transplant

Where to plant cucumbers outside

For the best possible chance of success, you’ll want to plant cucumbers in a sheltered and sunny location.  Growing cucumbers in pots (with appropriate support) means that it’s easier to move them around and follow the sun, and avoid the wind.  Cucumbers are a relatively delicate plant, so protection from the wind is key.

Spacing outdoor cucumbers

You can allow cucumbers to grow trailing on the ground.  It’s not necessary to support them vertically.  I prefer to have them supported, so save space on the ground.  And in pots, it’s easier (for me) to keep them controlled if they’re vertically supported.  If you’re going to let your outdoor cucumbers sprawl on the ground, then you’ll need to plant them about 90-100 centimetres apart.

Watering outdoor cucumbers

Water your cucumbers little and often.  They need lots of water but don’t leave them in soggy, waterlogged soil.  I tend to check the water content in the morning and the evening.  Water the soil or compost, not the plants, to try and avoid rotting and burning the fruits and leaves.

Feeding outdoor cucumbers

I’d feed outdoor cucumbers once every two weeks to ensure they get nutrients.

Pinching out outdoor cucumbers

If you pinch out the main growing stem on your outdoor cucumbers when you’ve got seven leaves, then you’ll get a better fruit yield.

Pollinating outdoor cucumbers

This is where things differ from growing greenhouse cucumbers.  You need the insects to pollinate your outdoor cucumbers, so just leave both the male and female flowers alone. 

Growing Cucumbers in a Greenhouse

You’ll need to bear in mind there are differences if you have a heated greenhouse versus if you have an unheated greenhouse.  (I’ve never had a heated greenhouse, but it’s something I aspire to!)

When to plant cucumbers in a greenhouse

Plant cucumber seeds in a heated greenhouse in February or March.  If you had an unheated greenhouse, then wait to plant out until May.  Start your seeds off inside on a windowsill to get a head start.

Spacing greenhouse cucumbers

You’ll need to transplant cucumber plants about 45 centimetres apart.  If you’re growing cucumbers in a pot, then one per round pot (about 45 cm diameter), or if you’re growing cucumbers in grow bags, then only two cucumber plants per bag.

Watering greenhouse cucumbers

Cucumbers are 96% water.  Water cucumbers little and often.  It’s a good idea to spray water inside the greenhouse to keep the humidity level high.  If you get a lot of direct sun, then you might want to screen your cucumber plants to prevent scorching.

Feeding greenhouse cucumbers

Using a good liquid fertilizer on your cucumber plants every two weeks is a good feeding program for greenhouse cucumber plants.

Staking and side shoots on cucumber plants

Providing cucumber plants with a vertical stake to climb can encourage side shoots, which means you’ll get a bigger yield on your cucumber plant.  Doing this in a greenhouse is easy.  Run a wire from one end of the greenhouse to the other.  Push a cane into the soil or compost beside each cucumber plant (do this at the time of planting, so as not to damage growing roots).  The wire will support the vertical canes and you can tie in the cucumbers to the canes and wires as they grow.  In this way, you’ll be training the main cucumber shoots to climb. 

supporting cucumbers

Pinching out growing stems and side shoots

Pinch out the top of the main growing stem when it reaches the top of the support.  This means that your cucumber plant will then focus its growing energy on the side shoots.  As the fruits begin to develop pinch out the ends of the side shoots, and then your plant will focus on the fruits.   If you only let the plant have two leaves after each fruit, then you’ll be encouraging more side shoots, which in turn provides a bigger yield.    If there are no flowers on a side shoot, then pinch it out after about 60 centimetres.

Remove Male Flowers on Greenhouse Cucumbers

You’ll want to remove the male flowers on greenhouse cucumbers, as if they pollinate then you’ll get a bitter-tasting cucumber.  Male flowers have a thin, plain stalk when compared with the female flower which has an immature cucumber between the stem and the flower.

Using a Cucumber Trellis to Support Cucumber Plants

Whether you have a greenhouse or not, supporting the cucumber plant, is, for me, a better way of producing and managing the fruit.  (I always like to maximise what I’m doing with my ground space, so growing cucumbers vertically rather than letting them lie on the ground is my preferred option.

cucumber aframe

This steel (folding) A-frame is a great option to provide support for climbers such as cucumbers.  It reduces the stress on the roots.  The feet fit firmly into the ground to secure it and it can also be used for squashes, courgettes and aubergines.  I like that it folds down at the end of the season and stores easily. 

Here are some other options for supporting cucumbers.

Harvesting Cucumbers

Cucumbers tend to ripen from mid-summer to mid-autumn in a greenhouse.  Outdoors this is likely to be a slightly shorter time.    The size that your cucumbers will grow to depends on the variety that you’re growing, so always check the growing instructions on your seed packet.

Cucumbers typically take about 12 weeks to grow to maturity. Some varieties will have different maturity times, so check the details on your seed packet.

Smaller cucumbers tend to be best when they’re about 10 centimetres long.  Longer cucumber varieties tend to be between 15-20 centimetres.    You’ll want a fruit that is firm and uniformly green.  Although they’re not quite magically prolific as courgettes, they do grow rapidly, so check them regularly.  If your cucumber goes soft and/or yellow, then it’s overripe.

The best time of the day to harvest cucumbers is the early morning. 

When your cucumbers are ready, use a sharp knife or secateurs and cut the stem cleanly.  If you harvest regularly you’ll encourage more fruiting!

Common Problems Growing Cucumbers

Although growing cucumbers is relatively easy, there are some common problems that you might encounter.  Keep a close eye out and deal with problems promptly to avoid affecting other plants in your garden.

Yellow Mosaic in Cucumbers

Mosaic, or yellow mosaic, is a cucumber virus spread by aphids.  Cucumber plants and leaves become stunted and deformed, with leaves showing a yellow mosaic pattern.  Flowering will stop or not even start.  Fruit that does appear will be inedible (don’t try it), pitted, small and hard.  If your cucumber plant is infected with cucumber mosaic virus you need to remove the infected plants and destroy them immediately as it will quickly spread to other plants.  Do NOT put it in the compost heap.  (Our beginner guide to composting is here)  Wash your hands immediately after handling any infected plants as you WILL spread it to other plants if you don’t take precautions

Powdery Mildew in Cucumbers

Powdery mildew in cucumbers shows itself as white patches on the leaves, which will also become small and shrivelled.  Cucumbers with powdery mildew produce inedible fruits.  The best way to avoid powdery mildew in cucumbers is to keep your soil or compost moist.

Whitefly in Cucumbers

Whitefly are white, small insects that suck the sap of the plants and excrete a sticky goop on the plant.  This encourages the growth of black mould.  They’re a disaster in the garden.   Keep them bay with sticky traps in the greenhouse, and regularly spray the underside of leaves with a soap-based spray.

Tips on Growing Cucumbers

  • Water cucumbers little and often.    Water the soil or compost at the base of the plant, not the leaves or fruits.  (here’s our guide to the best hoses for vegetable gardening)
  • If you’re growing cucumbers vertically, then use a support frame, a frame or a tomato cage to help support the plant and fruits.  Put the support in when you transplant to avoid damaging roots.
  • Take care when you transplant cucumber plants take extra care, the roots are very delicate.
  • Vertically growing cucumbers tend to help with managing insects and rot.
  • Feed with a good liquid fertilizer every 10-14 days.
  • When the fruits are ready, harvest regularly to encourage the plants to make more vegetables. If you don’t pick the cucumbers daily, you will have a shorter growing season and your yield won’t be as high.

FAQ’s on Growing Cucumbers

Got questions about growing cucumbers? Or want to know more about how to grow cucumbers and we haven’t answered your questions?  Check out our frequently asked questions about cucumber growing below, or ask us yours in the comments.

What’s the best way to grow cucumbers?

The key thing with growing cucumbers is selecting the right site.  If you’re growing cucumbers outdoors, then you’ll want sandy loam soil or a good vegetable compost.  You need full sunlight and a position that is sheltered from the wind. 

How long does it take for a cucumber to fully grow?

It takes between 50 and 70 days for cucumber fruits to reach maturity.   Pick them when they are mature, otherwise, they develop a bitter flavour when overripe.

Do you pinch out cucumber plants?

Yes.  Pinching out cucumber plants means that you will focus the cucumber plant on developing more side shoots and also more fruits.

How long after flowers do cucumbers appear?

You’ll likely see flowers on cucumber plants from about 45-55 days after germination.  This will usually be a male flower (unless you’ve gone for a female-only variety), then a female flower 14 days after that.  After the female flower has appeared it will be 10-14 days before the fruit starts to appear.

Can you use tomato cages for cucumbers?

Yes.  You can use a wire and cane to support cucumbers, or you can use an A-frame (like this one) to support cucumber plants.  Alternatively, tomato cages are one of the favourite gardening hacks to support cucumber plants.

How do you know when cucumbers are ready to be picked?

First of all, check the instructions on your cucumber seed packet, or plant if you bought a cucumber plant.  Usually, you’ll pick cucumbers when they are a uniform green colour, at the right length for the variety and firm.

Can cucumbers grow in pots?

Yes.  Growing cucumbers in pots is a great option.  It’s best to grow cucumbers in either plastic or ceramic pots that retain moisture.  You’ll need holes in the bottom for drainage and you’ll want a decent sized pot – check your seed packet for the space each plant needs.

Final Words on How to Grow Cucumbers

Own grown cucumbers taste amazing.  And they’re easy to grow.  You don’t need a greenhouse to grow cucumbers in, but it can (obviously) extend your growing season.  (these greenhouses are cheap, cheerful and easy to use).  You can grow cucumbers both outdoors and in a greenhouse, and you’ll need to take into account your local environment and the variety of cucumbers that you want to grow.  You don’t need heaps of space to grow cucumbers, you can grow cucumbers in pots and containers and you can grow cucumbers in bags or directly in the ground.    My favourite way to grow cucumbers is vertically in a pot, what’s yours?

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