There are many reasons why cucumber leaves turn yellow. The most common reasons are nutritional deficiencies, water related problems, lack of sunlight, and plant diseases and pests.The following content also has some reference value for raised garden beds.

Cucumbers require continuous watering, warm and sunny conditions, and fertile soil because they are heavy feed. Therefore, their growth depends on the quality and quantity of nutrients they receive. If the situation is severe or not resolved in a timely manner, these plants can also be affected by various problems, leading to yellowing of leaves (a condition known as yellowing) and even death.

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Common causes of cucumber leaf yellowing

The yellowing or yellowing of cucumber leaves is usually due to nutrient deficiencies, water issues, lighting issues, plant pests, and plant diseases. Let's take a closer look at these reasons:

Nutritional deficiency

As mentioned above, cucumbers are considered heavy feed, which means they require a large amount of nutrients to grow and produce normally. If there is a lack of any key nutrients, the leaves of cucumbers will turn yellow.

In this situation, if you want to accurately determine whether your plant lacks any major nutrients, you need to test the soil in the garden. Some common nutritional deficiencies can cause cucumber leaves to turn yellow, including:

Nitrogen deficiency

Nitrogen is the main nutrient for the growth of any plant. Nitrogen deficiency not only causes cucumber leaves to turn yellow, but also hinders growth. In severe cases, this situation may lead to the ultimate death of the plant.

Therefore, it is best to pay attention to signs of nitrogen deficiency in the garden, as timely detection of this problem is easy to solve. Note that the old leaves of cucumber plants turn yellow at the leaf tips or central veins, while the new leaves remain green.

You can easily solve the problem of nitrogen deficiency by applying a layer of 2-inch compost or 1-2 tablespoons of nitrogen fertilizer (such as ammonium nitrate). However, avoid using too much fertilizer in the soil of the garden as it may affect cucumber production.

Potassium deficiency

Cucumber is one of the few crops that requires potassium instead of nitrogen. Some common signs of potassium deficiency are yellowing at the edges and tips of the leaves, while the fruits are often rod-shaped. In addition, newer leaves are often small and dull, with wrinkles or cup-shaped features.

Fortunately, you can solve this problem by adding balanced fertilizers. If necessary, you can also treat the soil with alkalinity or acidity.

Plant pests

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There are various types of plant pests, including insects that extract juice from leaves. Sucking tree sap is one of the most common causes of leaf discoloration and yellowing. Common plant pests include:

Leaf mite

These cucumber leaves are very attractive and usually appear below the leaves. Spider mites cause yellow dots.


Aphids are small oval shaped insects that also attach to the underside of cucumber leaves. These pests are mainly yellow or green, leaving a sticky black substance on the leaves called honeydew.

To eliminate these pests, you may need to consider using safe and environmentally friendly insecticides.

Plant disease

In some cases, plant disease may also cause yellow stripes or spots on cucumber leaves. The following are diseases that cause yellowing of leaves:

Fusarium wilt

This disease is caused by cucumber beetle larvae that feed on plant roots, causing leaves to turn yellow from the edges and spread inward. In order to control diseases in the garden, you should remove infected plants.

Another common disease that causes cucumber leaves to turn yellow is verticillium wilt. If you plant cucumbers, tomatoes, eggplants, potatoes, and chili peppers in your garden, this disease is very common.

Cucumber mosaic virus

Cucumber mosaic virus can cause wrinkles on plant leaves and bend downwards to form yellow spots. Just like wilt disease, you only need to remove infected plants from the garden to control this disease, as it is easily spread by plant pests such as leafhoppers or aphids.

Downy mold

This is another common plant disease that can also cause cucumber leaves to turn yellow. The common sign is the yellow spots on the upper side of the leaves, which later turn brown. To manage and prevent this disease, you need to plant cucumber varieties with high resistance, remove infected plants, and improve air circulation around the plants.

Lack of sufficient sunlight

If your cucumber cannot receive enough sunlight, some leaves may turn yellow and become weak. Therefore, you should place your garden in a sunny area, or if they are placed in movable containers, move them to a sunny area for at least 6 hours per day.

Water related issues

Water is one of the basic requirements for the growth of any plant. However, watering plants like cucumbers too much can cause their leaves to turn yellow. Excessive watering can lead to oxygen deficiency in the roots, leading to yellowing and ultimately withering of the leaves. Remember, cucumber plants only need 1 to 2 inches of water per week.

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To prevent this problem, plant cucumbers in containers with drainage holes or on raised seedbeds. If there is a problem with soil drainage, you can also consider adding sand to loosen the soil.

Compared to many plants, cucumbers are relatively easy to grow. However, if the problem is severe, they are also prone to problems and conditions that can cause the leaves to turn yellow or eventually dry out.

We have discussed some common causes of cucumber leaf yellowing and provided practical solutions to help you identify, manage, and prevent this problem.

June 10, 2023

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