Cucumbers are amazingly productive if you treat them right. They are vining plants that grow best vertically, so they will need trellising or training and, since they grow so fast, a lot of pruning. There are a couple of ways you can go about pruning, and this article will give you a deep understanding of how, when, and why you should prune cucumber plants.

While you don’t have to prune cucumbers to get fruit, pruning reduces the chance of powdery mildew and increases productivity in many varieties. You can train your cucumbers to grow single-stem by regularly pruning the suckers off, or allow them to grow freely and only pick the male flowers.

Unlike tomatoes, cucumber suckers will turn into branches and produce just as generously as the main stem. However, to facilitate air-flow and ease of picking, many gardeners and most commercial growers will train their cucumbers to grow a single stem.

Let’s differentiate the three different types of pruning, and which one applies best to your style of gardening:

Training the cucumbers to grow in a single stem

As I mentioned, this style of growing is mostly reserved for greenhouses. You don’t really need to single-stem your cucumbers out in the field or in your home garden.

Single stem cucumbers will grow tall up on a string or a bamboo pole. Despite their many tendrils, once the plants bear fruit, they might fall off the string, so you still need to loosely secure the main stem to the string with a clip or a loose tie.

Once the cucumber plants get to a decent size, it’s time to check each node of the main stem for pruning. Cucumbers grow much faster than tomatoes, so while you might be in the habit of pruning your tomatoes 1-2 times a week, you’ll need to check your cucumber plants for suckers daily.

Here’s how to identify what you need to discard. On every stem node, you’ll find the following structures:

  • a branch or leaf;
  • a cucumber fruit and flower;
  • a tendril;
  • a sucker.

The only thing that needs removing is the sucker. Do this when it forms a small leaf – any sooner, and you might harm the fruit. Don’t wait too long, though, since suckers can easily get out of control.

Only pruning the male flowers

You may have noticed that we didn’t say anything about male flowers when growing greenhouse cucumbers. That’s because the most popular varieties grown in sheltered locations like greenhouses and polytunnels are hybrid, seedless cucumbers.

These types of cucumbers are called gynoecious varieties. They produce female-only flowers and have a concentrated harvesting period. Examples of hybrid varieties include Stonewall and Calypso.

By contrast, older cucumber varieties are monoecious plants. They produce both male flowers that produce pollen for pollinating the female flowers, and the fruits can be harvested for a much longer period. The best way to know which type of cucumbers you’ve sown is to check the seed packet and research whether it’s a hybrid or a classic variety.

What often happens with older cucumber varieties is that they tend to produce many more male flowers than female flowers, which can impact yield. This happens because:

  • The plant is still young. It tries to build enough pollen reserves for when the female flowers start forming.
  • The plant doesn’t have access to enough nutrients, especially nitrogen. It takes far less energy to produce male flowers, so the plant doesn’t prioritize producing fruit.
  • The plant doesn’t have access to pollinators – because of shade or weather conditions. This will also stimulate male flower production.
  • The temperature is too high – low temperatures stimulate female flowers (60°F / 16°C and below), while high temperatures (86°F / 30°C and above) lead to more male flowers.

While a ratio of 8-9 male flowers to one female flower is normal, you still want to promote as many fruit-bearing flowers as possible. One way to do that in your garden is by regularly picking male flowers. This will stimulate the cucumber plant to set more female flowers. Don’t prune ALL the male flowers, though. The plant still needs that pollen.

Topping off the cucumber plant for productivity

A little-known fact about growing cucumbers is that you can top them off (just like peppers) and they will start growing and producing more vigorously. This is because the main cucumber stem produces many more male flowers than female, while the second and third-generation branches of suckers have that ratio reversed.

Try this simple, step-by-step technique to top off you cucumber plants for maximum yield:

  1. Allow the first stem to develop at least six sets of leaves. Don’t prune off the suckers. Count to six sets of leaves (or 11-12 leaves total) and snip the top off with a pair of clean shears.
  2. The suckers will continue to grow, forming second-generation branches. Repeat the process, counting six sets of leaves on the suckers and top the 2nd generation branches off. At this point, the 2nd generation stems will be producing more female flowers, along with male flowers.
  3. The second-generation stems will produce suckers that then turn into 3rd generation branches. These branches will exclusively produce female flowers, and there’s no more need for pruning.

An important note: Be careful to only prune a couple of the 2nd generation branches, because you will still need plenty of male flowers to help pollinate the female flowers.

If you’re still not quite sure how to go about this topping off method, this video explains the method beautifully:

YouTube video

More useful tips for growing cucumbers

If left unattended, cucumbers will sprawl on the ground and occupy precious garden space which could be used for other purposes, especially in a small garden.

The best way to grow cucumbers outdoors is to train them up on a trellis. You can build this trellis yourself, using a pallet, a cattle panel, or sturdy posts and a trellis netting. Or you can take a shortcut and buy ready-made cucumber trellises like this one.

You can start cucumbers directly in the ground in early summer. Although they don’t like their roots disturbed, I’ve successfully started cucumbers in pots and transplanted them out in the garden when they were 2-3 weeks old. Aim for 2-3 plants per person to have an abundant supply of cucumbers all season long.

Don’t be impatient and start them too early, as cucumbers are very sensitive to cold weather. Allow for at least 8 hours of sunlight and ensure that the soil is well-drained. Stay on top of watering but don’t waterlog them to prevent root rot.

Once cucumbers start producing, the more you’ll pick them, the heavier they’ll crop. Much like beans, if one single cucumber is left to ripen for seed, the entire vine will stop producing. So check the vines regularly for hidden fruit – especially at the base of the plant.

Lastly, choose mildew-resistant varieties since cucumbers are prone to fungal disease, like most cucurbits. It’s best to spray them preventatively before they show any sign of powdery mildew. I like to use Neem oil for this purpose.

Keep in mind, though, that fungal disease towards the end of the season is normal, merely a sign that the leaves are getting old and the plant will soon stop producing.

Hopefully, you’ve found these tips useful. Experiment with varieties and pruning techniques to see which one you like best. Until next time, happy gardening!

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