Why are my cucumber leaves turning yellow?

While cucumbers happen to be one of the most popular crops among gardeners across the world, growing them is definitely a struggle for them. Aside from cucumbers being heavy feeders, a significant issue for farmers and gardeners cultivating the plant is the yellowing of its leaves. So, why are the cucumber leaves turning yellow?

Well, these plants need a lot of moisture to thrive. In a lot of cases, a lack of moisture or nutrients is the main culprit for the leaves of the cucumber plant to turn yellow. Of course, this doesn’t stop here. There are many other reasons as well, like diseases, chlorosis, and pest infestations.

Read this article to gain a clear understanding of why cucumber leaves turn yellow and what can be done about it. Let’s dive into the details.

yellow leaves

Table of Contents

Why are my cucumber leaves turning yellow?

Now that you’ve noticed the leaves of your cucumber plant changing to yellow, here are a few important causes along with solutions to save your harvest. Cucumber leaves and the whole plant turning yellow are not a small issue. If left unattended, the plant may die even before producing fruits. So, if you see cucumber leaves developing an unhealthy yellow shade, especially during the growth phase, pay attention.

Cucumber leaves with a yellow tint or spots can be seen for a variety of reasons, including:

1. Insufficient light

The main reason behind the yellowing of cucumber leaves can be insufficient light. It doesn’t matter whether you’re growing the plants indoors or outdoors, you’ve got to make sure that they’re getting adequate sunlight. Cucumbers require 6 – 8 hours of light exposure every day.

Solution

  • Shift your plants to a location where they’ll receive a minimum of six hours of sunlight.
  • In the case of indoor plants, use fluorescent or LED supplementary lighting.
Insufficient light for cucumber

2. Overwatering or underwatering

A cucumber plant thrives only when it receives the right amount of water. Overwatering leads to a shortage of oxygen in the roots, which makes the leaves turn yellow followed by wilting. Insufficient water can also be the culprit for yellowing leaves. Keep in mind that the cucumber plant needs 1-2 inches of water every seven days. 

Solution

  • Water your cucumber plants regularly.
  • Choose to grow these plants in raised beds.
  • If there are drainage issues in the soil, try to loosen it by mixing some sand into it.
  • There are gadgets to measure soil moisture. Use them to prevent overwatering or under-watering your cucumber plants.
Overwatering cucumber plant

3. Chlorosis

Chlorosis is a condition in which the leaves produce inadequate amounts of chlorophyll, the green leaf pigment required to produce food for the whole plant. If there isn’t sufficient chlorophyll in the leaves, they start turning yellow, an indicator that they’re starving for food.

Solution

In the case of chlorosis, you should find out what exactly is causing the condition. you can study the plant for other signs and symptoms. Most plants with this condition tend to suffer from iron deficiency, which you can easily treat using sprays.

4. Pest infestation

Pests are also one of the main reasons behind the discolouration of cucumber leaves. The most common pests that attack the cucumber plant include spider mites, leafhoppers, aphids, and whiteflies.

Spider mites

spider mites can wreak havoc on cucumber plants. They suck the sap from the leaves and damage them. You can spot these pests on the underside of the leaves, as they leave a silver-coloured web.

Solution

  • Avoid creating dry or dusty conditions.
  • Use garlic, neem, clove, or rosemary essential oils on your plants.
  • Spray an insecticidal soap as soon as you spot the mites.

Whiteflies

Whiteflies infestation also often leads to the yellowing of cucumber leaves. These are normally found on the backside of the leaves, where they feed on sap.

Solution

  • Shake the cucumber plant.
  • Make use of row covers and reflective mulches.
  • In the case of a severe infestation of your cucumbers with whiteflies, you’d better discard and dispose of them.

Aphids

Aphids are small oval bugs with long mouths that can make your cucumber plant stunted and mottled. These insects tend to suck out the fluids of your plants. It is not easy to control them. Hence, you must get rid of them at the earliest possible time. If you notice your cucumber leaves are bent downwards, especially at the edges, they are likely to be attacked by aphids.

Solution

  • Avoid planting your plants near the woods or weedy areas.
  • Use an insecticidal soap or spray neem oil on the underside of the leaves or aphids.

Potato leafhoppers

These insects are larger than the other bugs mentioned above. You can see them on the leaves of your cucumber plant, where they suck the sap out. They inject toxins as they feed. Eventually, the leaves become weak and turn yellow.

Solution

  • The moment you spot the nymphs, apply an insecticide.
  • Use a hose to spray powerful blasts of water on the plants.
  • Use insecticidal soap.
  • Shield the plants with row covers or screens.
aphids on cucumber plant

5. Plant diseases

Bacterial and fungal plant diseases are most often responsible for the yellow spots you see on cucumber leaves. These diseases can even lead to the death of your plants. The most common cucumber diseases include cucumber mosaic virus, downy mildew, and fusarium wilt.

Cucumber mosaic virus

If you see mild mosaic patterns, flecking, mottling, and fern leaf distortion, it could be a sign of the cucumber mosaic virus. The virus spreads by aphids, and in a very short period, the whole plant will get infected, and in a few hours, the virus will spread to the other plants as well.

Solution

Getting rid of the entire plant is the only way to eliminate the disease, and prevent it from spreading to other plants.

Fusarium wilt

This disease is caused by a type of fungus named Fusarium oxysporum f. sp. Cucumerinum. It is capable of persisting for long periods in the soil in the form of durable spores or along with plant debris. The symptoms include stunting, yellowing, and wilting of your cucumber plant.

Solution

Removal is the only option to get rid of this fungus and save your other plants from the disease.

Downy mildew

Downy mildew is caused by Psuedoperonospora cubensis, which thrives in humid or wet conditions. If you see yellow spots forming on the leaf surface that eventually spread and turn the leaves brown, it’s a possible sign of downy mildew.

Solution

  • Space out your plants so that they get good air circulation and can dry out.
  • If you notice signs of this disease, apply fungicides. However, you should do it in the early stages of the infection.
  • Remove plants that are fully infected.
cucumber Downy Mildew image

6. Nutritional Deficiency

Like other plants, cucumbers also need several nutrients to thrive. To determine if your plant is suffering from nutrient deficiency, you should have your garden soil tested. Listed below are the common deficiencies that lead to the yellowing of cucumber leaves. 

Nitrogen deficiency

If the nitrogen levels are low, cucumber leaves will start turning yellow at the tips as well as along the central veins. Besides, plant growth also gets inhibited. To prevent further damage, use a high-quality fertiliser with the proper dilution rate and add a 2-inch layer of compost to increase the content of nitrogen.

Phosphorus deficiency

If your cucumber leaves turn bronze or deep yellow, it could be due to phosphorus deficiency. These plants have weak roots and show stunted growth. What you can do is supplement your soil with a fertiliser containing phosphorus regularly.

Potassium

If your older leaves are first affected, it could be a sign of potassium deficiency. The tips and edges of the leaves first turn yellow, which slowly spreads between the veins and continues toward the middle part of the leaf. To prevent this problem from escalating, you can treat your soil for acidity or alkalinity. Besides using a well-balanced fertiliser, you can also bury citrus rinds in the soil surrounding the affected plants.

Zinc

A zinc deficiency makes your leaves turn yellow and droopy. Besides the size of the leaves becoming smaller, the entire plant shows stunted growth. The best way to treat zinc deficiency in cucumber plants is to spray organic kelp or a zinc sulphate solution.

Iron

If your plants develop interveinal chlorosis, it is due to an iron deficiency. The leaves turn yellow while the veins remain green. The older leaves stay green as well. Treatment involves spraying liquid iron on your plant leaves and using chelated iron in granular or powdered form to treat the soil.

Magnesium

In the case of magnesium deficiency, older cucumber leaves turn yellow. If the deficiency is severe, you can see a light tan burn in the yellow areas. The fruit yield also decreases to a great extent. The best treatment is to apply soluble magnesium nitrate sprays or Epsom salt solution.

cucumber plant nitrogen

Conclusion

The answer to your question, “Why are my cucumber leaves turning yellow?” is that it could be because of several reasons. Finding the specific cause can help you save the plant.

To recap:

  • Make sure your cucumber plants get sufficient water.
  • Your plants should get 8-10 hours of light every day.
  • Have an eye on pest infestations and act immediately. 
  • Use fertilisers, preferably organic, to meet the nutrition needs of your plant.
  • If you observe a plant disease, take the necessary steps to save the plant.

I hope this information will help maintain your cucumber plants in good condition.

healthy cucumber plant

People Also Ask

How often should you water a cucumber plant?

Cucumbers require a total of 1 to 2 inches of water a week; it doesn’t matter if it’s you or the rain doing the watering. Well, this might not be easy to measure, so decide the watering frequency by checking how the soil feels when you examine it. Water your cucumber plants when the soil feels dry at about one inch below the surface. 

Can you eat a yellow cucumber?

While eating a yellow cucumber might not hurt you, you probably don’t have to try it. These fruits become yellow only when they have not appropriately ripened or are lacking the right growing conditions. Yellow cucumbers generally taste very bitter and have an unappetizing taste. 

What is a homemade fertiliser for cucumbers?

It’s not a good idea to fertilise your lawn in the middle of the day, because the plants may suffer from chemical burns. The best option is to apply fertilizer in the morning when the weather is usually cool. Also, make sure there is no rain forecast for the day. Morning application not only allows the fertilizer to soak in the soil before it gets too hot but also reduces the risk of it getting washed away.

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Oliver Wright
Oliver Wright

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