Cucumber has many uses, hence having endless reasons to appear in your garden. It is a fruit, but we also consume it as a vegetable in fresh salads. Apart from consumption, the cucumber plant also adds good looks to your garden. The curling tendrils, sprawling vines, large leave and yellow flowers give your garden a fresh look. However, like any other plant, the cucumber plant needs good attention and care. If you do not meet the plant’s requirement, it may become unhealthy, and you may see cucumber leaves turning yellow.

Continue reading if you want to know the requisites of its healthy growth and the causes of cucumber leaves turning yellow. Lastly, the possible solutions.

Basic Requirements for Healthy Growth

Cucumber plants need dry and warm conditions to grow healthily, the ideal temperature being 30 degree Celsius. The soil must be well-drained and rich in organic matters to yield the best fruit. Cucumber plants have a shallow root system that provides them with enough soil moisture. You must also try to plant them in a place with direct exposure to the sun, as they are very sensitive to cold.

Make sure you plant cucumbers in a spacious area, as the sprawling vines need room to grow. However, you can always provide vertical support. Cucumber plants need an extensive supply of water. Ensure you deep-water them at least once a week, reaching the depth of an inch. When the cucumbers are green in color and still immature, you must harvest them. The size of the cucumber while harvesting depends on the variety you’ve grown.

Why Do Cucumber Leaves Turn Yellow?

The reason for cucumber leaves turning yellow is the lack of chlorophyll. We call the process chlorosis, where the leaves lose green coloration. The presence of chlorophyll is crucial for every plant, as it’s responsible for transforming sunlight into chemical energy. The absence of chlorophyll means the plant lacks that function, compromising its healthy growth.

But what exactly causes the lack of chlorophyll? In the next section, we’ll have a look at the causes that ultimately lead to cucumber leaves turning yellow.

The Causes

Below are a few causes for cucumber leaves turning yellow. We’ll have a look at each one of them in detail.

1-) Plant Diseases


If your cucumber plant’s leaves start to turn yellow, a plant disease might be responsible for the yellow marks or streaks. Continue reading to know about the common diseases and identify if your plant has any of these.

a-) Downy Mildew


The main symptom of downy mildew is the appearance of yellow spots on the leaves’ upper surface. Veins in the leaves border these spots, making it look like a delicate patchwork. These spots later turn brown. In case your area experiences high humidity, grey fuzz can appear on the underside of the leaves, as well.

On finding these signs, take immediate actions to prevent the disease from spreading further. The basic solution is to remove the cucumber plants severely infected by the disease to stop it from spreading. Next time you plant cucumbers, use the variety more resistant to diseases. Maintain more distance between the plants to allow extra air circulation and use drip irrigation. If you spot the symptoms early, purchase fungicides that help fight against downy mildew disease.

b-) Mosaic Virus

Mosaic Virus

In addition to cucumber leaves turning yellow, if they also shrink and face downwards, Mosaic Virus may have infected them. The disease can spread to other plants quickly, and leafhoppers and aphids may carry this virus with them.

The best solution to tackle the virus is to remove the plants already infected by it. We recommend changing the soil when you remove the infected plants, as this disease can live in the soil, as well.

c-) Fusarium Wilt

Fusarium Wilt

More popular with older leaves, the Fusarium Wilt disease causes them to start turning yellow at the edges and spread inwards. This disease also extends very quickly to other plants. The main reason is the cucumber beetle larvae that feed on the cucumber plant’s root and carries the virus around.

A very similar disease is the Verticillium Wilt. It can only infect your cucumber plant if you sow them in an area previously used for vegetables. Like Mosaic Virus, the only practical cure to these diseases is removing the infected plants as soon as you see the signs.

2-) Pests


Another reason for cucumber leaves turning yellow are plant pests. You might have already come across many insects on your plants, but they can also suck the sap out of leaves. It, in turn, leads to discoloration and causes your leaves to turn yellow.

The common plant pests include:

a-) Whiteflies


Whiteflies are small, winged insects that take residence on your plant leaves. To find out whether this pest infects your plant, give them a little shake. If whiteflies exist near or on your plant, you’ll see them rise in a white cloud.

Whiteflies can leave a sticky black substance known as honeydew on your plant. The best way to get rid of the whiteflies is to spray insecticidal soap on your cucumber plant.

b-) Aphids


Aphids are also pests you must keep your eye out for. These small, oval-shaped insects can be the cause of your cucumber leaves turning yellow. They usually take residence on the underside of cucumber leaves.

Use insecticidal soap and spray on your plants to keep the aphids away.

c-) Spider Mites

Spider Mites

Spider mites might be another reason for your cucumber leaves turning yellow. They feed on cucumber leaves and cause yellow patches on the surface. These insects, unlike the other two we have discussed, leave silvery webbing behind on the plant. If you see any such thing, take immediate action. Begin by checking the underside of the leaves because that’s where they like to hide.

d-) Potato Leafhopper

Potato Leafhopper- Cucumber Leaves

The potato leafhopper is easier to spot than other pests due to its size and can be immensely dangerous for your plants. They feed on the plant and deprive them of the sap, causing cucumber leaves turning yellow. When they feed, they inject a toxin into the plant that magnifies the yellowing. The toxin would eventually cause the cucumber leaves to fall off the plant.

The common way to get rid of the potato leafhopper is to use insecticide. But we do not suggest its usage on edible plants such as cucumber. Hence, keep your garden free of any weed and use protective covers over the plants to keep the insects away.

If you’re more into houseplants, check out how to get rid of bugs in houseplants.

3-) Lack of Nutrients

Lack of Nutrients -Cucumber Leaves

The cucumber is a demanding plant when it comes to nutrition. The common reason why chlorosis occurs is the lack of these nutrients. The best way to identify whether your plant lacks the required nutrients is to test your soil.

The following are the most typical deficiencies that result in cucumber leaves turning yellow.

1-) Zinc Deficiency

Zinc is a vital nutrient helping your plant to grow. Zinc deficiency comes with too small leaves for their age and slowed growth. It’s common that between the veins, the older leaves would start turning yellow.

To tackle it, use organic kelp and zinc sulfate solution.

2-) Nitrogen Deficiency

Like zinc, nitrogen is very crucial for growth. Cucumber leaves turning yellow and restricted plant growth are the usual signs of nitrogen deficiency. The yellowing initiates at the edges of the leaves and around the central veins.

To overcome the deficiency, add more compost to the soil. Similarly, you can use 1-2 tablespoon of 6-10-10 fertilizer if you spot the problem early. When the flowers start to bloom, you can use a tablespoon of ammonium nitrate. But ensure to use fertilizers to a minimum amount, as they affect the growth of fruits.

3-) Potassium Deficiency

Cucumber plants need more potassium than nitrogen. Therefore, a deficiency of this nutrient can severely affect them. The symptoms include cucumber leaves turning yellow at the tip and edges. Young leaves would shrink and become small, and they do not have a bright look to them.

You can overcome the potassium deficiency by checking the soil for alkalinity or acidity and using a balanced fertilizer.

4-) Iron Deficiency

Iron deficiency is tricky to identify. The older leaves would still be green, and the newer leaves would have green veins but a yellowish look.

To tackle the deficiency, spray liquid iron on the plant. You can also add powdered chelated or granular iron to the soil near the cucumber plant’s root.

What’s the Solution?

Cucumber leaves turning yellow is a critical issue. The solution begins by identifying what’s causing the cucumber leaves turning yellow. Once you’ve discovered the reason, follow the ways we have discussed above to tackle them. For example, if you find out that pests cause cucumber leaves turning yellow, immediately use insecticidal soap.

As important as water is to cucumber plants, do not overwater them. Remember, they need up to 2 inches of water daily, and overwatering can lead to a lack of oxygen in the roots. Also, make sure the soil does not have any drainage problems and, if so, try combining it with sand.

Cucumber plants also need sunlight, and a lack of it results in cucumber leaves turning yellow. Try for at least 6 hours of sunlight per day. If that’s not possible at your current location, try relocating the plants.


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