As one of the most refreshing and versatile salad fruits in the world, cucumbers are something of a gardener’s favourite. However, while they may be a popular plant, they certainly aren’t without their problems and if you have ever tried to grow them in a greenhouse, you may be familiar with how delicate these fruits are. Cucumber plants may fall victim to a variety of diseases and parasites. If left untreated, your entire cucumber crop could be ruined. But the good news is that there are things you can do to prevent these problems and fix them should they occur. In this guide, we will be looking at the most common cucumber problems and giving you the best solutions.

Cucumbers Growing in a Greenhouse
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What Are The Most Common Cucumber Problems?

Some people prefer to use transplants from their greenhouse but it is worth keeping in mind that this could result in some stunted growth since cucumbers are highly susceptible to transplant shock. Some of the problems with growing cucumbers in a greenhouse are:

Lack of Pollination

Cucumbers require heavy pollination which may not be as likely in the greenhouse, even if you are leaving the door open to allow pollinators to enter. If your cucumbers seem to grow for a short while and then die off, you can try hand pollinating, or attempt to lure more pollinators in by growing plants that will attract them such as black-eyed Susans, basil, dill and sunflowers, among others.

Lack of Water

Signs that your cucumber plants may not be receiving enough water might include wilting, discoloured leaves and slower growth. Cucumbers have an extremely high water content and if you regularly keep one in your kitchen, you will notice how quickly it can dry out. The same applies to the plant. When you are growing cucumbers in containers, you will need to pay close attention to how much water they are receiving. Whereas some plants run the risk of being overwatered, you can’t give a cucumber too much.

Make sure that you direct the flow of water into the surrounding soil and allow it to soak all the way through to the bottom of the container before you stop the flow.

Lack of Nutrition

As well as providing the cucumbers in your greenhouse with a lot of water, you will also need to ensure that they receive the correct nutrition. Cucumbers grown in containers in the greenhouse will need a regular dose of organic fertiliser (like 3-4-6). You must ensure that you are using top-quality potting soil. If you notice that your plants aren’t flourishing, trying a different potting mix may solve the problem.

Healthy Cucumbers Growing in a Greenhouse
Healthy Cucumbers Growing in a Greenhouse

Diseases

There are several contagious diseases that could affect your cucumber plants and while some are curable others will require you to start from scratch.

Cucumber Mosaic Disease

The key signs of this disease are that the cucumber plant will stop growing and the leaves will develop a mosaic-like pattern that is yellow in colour. While it may have a fancy name, this infection will effectively end the life of a cucumber plant. This disease is spread by aphids which can be the bane of a gardener’s life and will cause problems both in and out of the greenhouse.

It is important that you discard the plant but also make sure to wash your hands before touching other plants as this can be incredibly contagious.

Powdery Mildew

You may walk into the greenhouse one day to find that the leaves of your cucumber plants are covered in a thin white powder that closely resembles talc the good news is that it is largely cosmetic. A good cure for powdery mildew on your cucumbers is to use baking soda. Mix 1 tablespoon of baking soda with 1 teaspoon of washing-up liquid and 2 litres of water. Give it a good mix and spray on the leaves of your plant including the underneath. That being said, there are disease-resistant varieties of cucumber such as Jackson and Eureka.

If powdery mildew becomes very heavy, this can make photosynthesis difficult and you may notice that the plant’s growth is stunted.

Pests

Cucumbers are very fragile and they are also susceptible to some pests that will happily eat your fruits before you get the chance to enjoy them for yourself. 

Red Spider Mites

Typically, red spider mites will affect the plants when the weather is warmer and they will cause the leaves to take on a rusty appearance. Red spider mites are one of the most problematic insects for greenhouse plants. It is therefore not surprising that if you choose to grow your cucumbers in the greenhouse, they may become a victim of these tiny animals.

For red spider mite infestations on cucumbers, promptly remove and discard the most affected areas. Use a forceful water spray to dislodge mites, avoiding young or sensitive plants. To deter mites, increase humidity with careful overhead watering (Note: wet leaves can contribute to plant disease).

Whitefly

Another common problem with cucumbers is the whitefly. These small flies that are very closely related to the aphid will suck the sap from the plant which will then result in a black residue, resemblant of soot. In turn, this can significantly stunt the growth of the plant. To get rid of whitefly off your cucumbers, first, spray leaves with your hose or spray bottle ensuring that you get underneath the leaves where the eggs and nymphs are likely to be. You can also use an insecticidal soap but it is best to use this in the evening when the temperatures are cooler.

Conclusion

While cucumbers are an incredibly popular plant among British gardeners, they aren’t without their problems. These plants will typically thrive best when planted in the ground but it is possible to grow them in a greenhouse. However, you must be prepared to face some issues, most of which are fortunately easily remedied.

Growing Cucumbers in a Greenhouse Infographic
Growing Cucumbers in a Greenhouse Infographic

Garden Doctor Tips

“Leave your greenhouse door open for parts of the day to let the pollinators in or you will have to pollinate the buds by hand!”

“Don’t be tight with your watering schedule, cucumbers need a lot of water in order to swell!”

“Don’t use any chemicals or pesticides on your cucumbers!”

“Grow sunflowers in your garden to attract plenty of bees and other pollinators that will pollinate your cucumbers!”

Frequently Asked Questions

Why are my cucumbers dying?

There are various reasons that your cucumbers could be dying. If they appear very small and seem to wither and die, it is likely due to lack of pollination. Other things that can cause plants to die are various pests and disease. 

Do cucumbers need a lot of water?

Yes, cucumbers require a lot of water once the fruits have set. Cucumbers are mostly made of water so giving them plenty to drink will help them swell and grow large. 

Are cucumbers easy to grow?

Cucumbers are quite fragile and are not self-pollinating which makes them a little trickier to grow for the average beginner. Once you have an idea of what you are doing, however, you will be able to grow and enjoy cucumbers with ease. 


Author

Trevor Wright is not just a seasoned horticulturist; he’s the esteemed Garden Doctor. With a BSc in Horticulture and years of hands-on experience in the soil, Trevor has become a trusted mentor for all things gardening. As the founder of Garden Doctor, he’s committed to clarifying the intricacies of gardening, offering straightforward advice that’s rooted in years of practice. His writing is a garden of how-tos, savvy insights, and comprehensive guides that enable individuals to nurture and grow their garden dreams. When he’s not knee-deep in garden beds, Trevor is at his keyboard passing on his green-thumbed wisdom to budding gardeners, ensuring that the legacy of sustainable and joyful gardening blossoms far and wide.


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