How to grow cucumbers in pots for a summer of tasty harvests — and the early mistake experts warn against that will sabotage your crop

Keen to grow your own cucumbers this year? Whether you’ve got a small patio, greenhouse or balcony, learning how to grow cucumbers in pots is a great way to make the most of your space.

Knowing how to grow cucumbers in the ground is one thing, but container growing is a lot more flexible. That’s why they’re a great choice if you’re working with small garden ideas.

'Cucumbers are a rewarding vegetable — they grow quickly and are relatively fast to produce fruits,’ says Mairi Devlin, head of gardening at B&Q. ‘With the right size pot, good quality soil, consistent moisture and a good amount of sun, you should end up with a great crop of cucumbers.’

Wondering how you can nail all three? We’ve thrown together a guide on how to grow cucumbers in pots for a summer of tasty harvests — and we're covering the one potting mistake first-time growers are prone to making.

What you'll need

• Cucumber seeds, like Cucumber 'Bella' F1 Hybrid Seeds from Thompson & Morgan
• A 9cm pot to start with, like The Flowerpot Men 9cm Plant Pots from Amazon
• A larger pot for later on, like the Helix Powdered Clay Planter Container from B&Q
• Good, peat-free compost like the Westland Bed & Vegetable Peat-Free Multi-Purpose Soil from B&Q
• Some fertiliser, like the Miracle-Gro Performance Organics Fruit & Veg Concentrate Plant Food from Amazon

1. Sow the seeds

If you're wondering when to sow cucumbers seeds, you can get started as early as February in a heated greenhouse. Generally, though, gardeners begin sowing indoors from March or April.

‘I always sow the seed individually into 9cm pots first, ruthlessly discarding any weak plants,’ says Annelise Brilli, horticultural expert at Thompson & Morgan. ‘Anything smaller than 9cm requires a second potting up stage, which just means more work and root disturbance.’

It’s important that you don’t start the seeds in a pot that’s too big. ‘Anything bigger than 9cm and the baby seedlings resent having their vulnerable roots swamped in an oversized pot!’ Annelise warns.

It’s also a good idea to use a heated propagator, because cucumbers love the heat, and keep them on a sunny windowsill.

Annelise Brilli

Annelise Brilli is the horticultural copywriter for Thompson & Morgan. Annelise caught the gardening bug from her mother, whose tiny backyard was crammed with a huge collection of plants.

2. Water correctly after seedlings emerge

Learning how to grow cucumbers in pots isn’t just about popping the seeds in the soil and hoping for the best — you’ll need to monitor their growing conditions especially well during the early stages of growth.

‘Be very careful with watering once the seedlings have emerged,’ says Annelise. ‘Too much water, especially around the stem, and they’ll rot.’

So, keep watering to a minimum. But don’t underdo it, either — consistently moist soil is key.

3. Transplant the seedlings into larger pots

Once your seedlings have developed two strong seed leaves (with a third just developing, according to Annelise), you can transplant them into bigger pots.

‘Plant a single seedling into a container at least 40cm wide by 30cm deep,’ Annelise says. ‘Cucumbers are vulnerable to neck rot, so plant with the neck of the stem just above the level of the surrounding soil.’

The best soil for the job? Annelise recommends a rich peat-free compost, with some added slow-release fertiliser to feed the hungry plants.

You’ll also need to position the pots somewhere sunny. ‘The cucumbers will grow best with 6-8 hours of sunlight a day,’ says Mairi from B&Q.

4. Water consistently

Now you’ve got your cucumbers planted in their final pots, you’ll need to make sure you’re watering them enough. In fact, watering is central to the flavour of the fruits.

‘My top tip for growing the tastiest cucumbers is to maintain an even moisture throughout their growth period,’ says Hannah Rowson, garden centre manager at J. Parker’s. ‘If your cucumbers dry out, then you risk the fruit turning bitter.’

Don’t overdo it, though — cucumbers hate soggy soil, so make sure your pots have plenty of drainage.

‘To achieve this sweet spot, dig in plenty of organic matter when growing them outside and use the best quality compost you can afford when growing them in pots,’ says Annelise.

Hannah Rowson

Hannah Rowson has been with bulb specialist J. Parker's for over 8 years. RHS qualified, Hannah is a fountain of knowledge for all things gardening and horticulture, and has even had her garden designs displayed at RHS Tatton Flower Show.

5. Consider support

Depending on the variety, you might want to learn how to grow cucumbers vertically.

'Cucumber plants do not necessarily need to climb, but as they grow quickly, supporting them with climbing structures is beneficial to their overall growth,' says Mairi from B&Q. 'Whether it's bamboo canes, netting, or a trellis, providing something for their tendrils to twine around helps them thrive.'

B&Q sells brilliant cucumber trellises like these heavy-duty frames, designed specifically for supporting heavy crops.

6. Harvest them

Cucumbers should be ready to harvest from the middle of summer, but the best way to tell is by looking at their size.

Usually, a length of six to twelve inches is a good way to tell that the fruits are ready but this varies by variety — so double-check the one you're growing to be sure. That way, you'll enjoy the best flavour.

FAQs

Should I pinch off cucumber flowers?

Once those signature yellow flowers start cropping up, it can be tricky to know what to do with them. It all depends on whether you’ll be learning how to grow cucumbers in pots indoors or outside.

‘If growing your cucumber plants in a greenhouse, then pinching off the flowers on the male plants prevents over pollination and will produce better tasting fruit,’ explains Hannah from J. Parker’s.

‘However, if you are growing your cucumbers outdoors, then your plants will be naturally pollinated by insects and pinching off the flowers won’t be necessary.'

Do cucumbers need full sun?

Cucumbers are fans of the sunshine, so a warm, sunny and sheltered spot is best. If you have a greenhouse, better still.

‘If you don’t have a greenhouse, choose a south- or west-facing spot outside with the shelter of a wall or fence,’ says Annelise from Thompson & Morgan. ‘They will tolerate light shade in the hottest summer months.’

And that's that! Now you know how to grow cucumbers in pots. If you're looking to fill another container, take a look at our guide on how to grow tomatoes in pots, too.