A Greenhouse Grower’s Guide to Cucumbers

Cucumbers are one of the most popular vegetables in the UK and are packed full of micronutrients and goodness. A staple in everything from sandwiches to salads, cucumbers are one of the most versatile summer vegetables you can grow.

Despite this, few people try their hand growing cucumbers and when compared to lettuces, tomatoes and other common garden vegetables, likely because they are perceived as being more challenging to grow. However, armed with the information in this guide, pretty much anyone with a greenhouse can grow cucumbers.

Which Type of Cucumber Should you Grow?

The two most popular groups of cucumbers are ridge cucumbers and greenhouse cucumbers. Ridge cucumbers, named for the small ridges along their length, are typically grown outdoors and tend to be smaller than greenhouse cucumbers.

In Britain, growing ridge cucumbers can be very difficult because they don’t respond well to temperate climates. Although some determined gardeners do have success with outdoor cucumbers, cucumbers grow far better in a warm, humid surroundings.

Greenhouse cucumbers, on the other hand, are the typical cucumbers you’d find at the supermarket or your nan’s sandwiches. They’re bigger than their ridged counterparts and completely smooth. As well as this they tend to be juicier and sweeter, which is why they’re more commonly sold than ridge cucumbers.

As a result of all these factors, most greenhouse growers opt for greenhouse cucumbers, as opposed to ridge cucumbers, and we recommend attempting a crop of ridge cucumbers only if you’re very experienced.

Cucumber Varieties

There are a number of different greenhouse cucumbers that you can choose from, but the better varieties can be quite costly. However, when weighing up which type to buy, keep in mind that cucumbers heavy-cropping plants, and therefore just a couple of well-grown plants are enough to expand the crop significantly and keep growing indefinitely.

The most popular varieties of cucumbers are the Telegraph and Conqueror, and both are solid choices – large, juicy and sweet. However, there’s more to choosing a cucumber than just its breed, as the sex of the plant also has a huge effect on the crop. Female flowers will grow cucumbers regardless of whether they have been fertilised, however, fertilised cucumbers are significantly more bitter than their unfertilized counterparts.

While you can simply remove male plants as and when they open to prevent fertilisation, this can be a lot of work and requires constant vigilance throughout the summer. As a result, there are many female only breeds that you can buy that will yield the sweetest cucumbers possible, with a lot less work for you. Some good all female varieties include Topsy, Birgit and Paska.

How to Germinate Cucumbers

Germinating cucumber seeds is arguably the most challenging part of growing cucumbers, and while getting the seeds to take can be tricky, given the right conditions good quality seeds should germinate quickly. The most important aspect is making sure that the compost you use gives the seeds the conditions they need to grow. Warm, moist, nutrient-rich compost will give your cucumber seeds everything they need to germinate.

Most cucumber growers plant their seeds quite early in the year. If it’s a warm year, planting as early as March or April will give you the longest possible cropping season. Earlier than March the greenhouse will still be too cold, but if you hold off, you’ll yield a smaller crop.

By following these steps, you should see your seeds germinate within weeks:

1. Take a small flower pot, fill it with multipurpose, peat-free compost and press the seeds into the compost. They should be buried around 1 cm deep in the compost.
2. Soak the pot in water for around 12 hours, until the compost is completely saturated and damp throughout.
3. It is important that the pots are kept very moist and humid. We recommend placing a clear plastic bag over the pot to retain as much moisture as possible.
4. The compost needs to be kept warm. Some growers opt to put the compost in an airing cupboard or near a boiler, while others find that a sunny windowsill is warm enough. Heat mats are the best possible solution, however, as they can maintain a constant temperature of around 20°C which is ideal for your seeds.
5. After a week or so, seedlings should start emerging from the compost. When this happens, move the pots to an area that gets a good amount of sunlight, such as a windowsill.

Transferring the Seedlings into a Greenhouse

When the seedlings have germinated, they don’t require the same level of constant heat. As they reach around 3” tall, they should be strong enough to survive being re-potted into their permanent positions. Cucumbers thrive in compost that is full of nutrients and organic matter, so a homemade compost that is dense in vegetable matter is perfect. Similarly, they need plenty of water to grow to their full potential, so keeping them well watered should be a priority. Like any plant, however, waterlogging can lead to root rot and other problems, so we recommend potting the adult cucumber plants in containers as opposed to the bare ground, as this makes monitoring water levels much easier.

Cucumbers do well in direct sunlight, and the more light they get, the faster they will grow. Because they are climbing plants, it’s a good idea to use garden canes and twine to support the growing stem and keep it upright.

Harvesting The Cucumbers

As the season continues, you should have a good crop of juicy, big cucumbers, but harvesting them can be a challenge in and of itself. Unlike most crops where the vegetables become ready at roughly the same time, cucumbers will come to fruition over the course of the season. Some cucumber plants may produce vegetables within a couple of months and will continue to grow more throughout the season.

Cucumbers should be picked regularly and early, as this directs more energy to the developing cucumbers, therefore speeding up the growing process and ultimately yielding a bigger crop over the course of the season.