Why are my cucumber leaves turning yellow

Why are my cucumber leaves turning yellow?

According to stats of 2019, cucumbers’ global production was 87.81million tons, which reflects how popular they are. Almost everybody loves them. If the cool has a taste, it would be a cucumber. Give your cucumber plants a warm sunny environment, consistent watering, and they will turn out to be your most producing plants.

There is nothing more hurtful than seeing your beloved cucumber plant declining. When your cucumber leaves are turning yellow, they severely need your attention. Cucumber plants are heavy feeders because when they do not receive enough nutrients, their leaves turn yellow and eventually die.

This article will discuss the possible causes of why your cucumber leaves are turning yellow and how to prevent them. Let’s begin:

Causes of their discoloration and possible solutions:

 Your cucumber leaves are turning yellow because of chlorophyll. Chlorophyll converts sunlight into energy. That’s why the lack of it is a threat to your cucumber plant. The cause of chlorophyll falls into five categories: plant insects, nutritional deficiencies, diseases, water, and sunlight. Let’s look at all of them one by one to find out all the causes and prevent them.


We all know that plants need sunlight to grow, so there is no exception that cucumbers need it too. If they don’t get sunlight, no nutrients, and water, the cucumber leaves start to turn yellow. Cucumber plants need 6 hours of daylight, but some cucumber plants enjoy 8 hours of sunlight daily. If they are not getting enough sun exposure, put them in a place where they can receive the most sunlight.


Water is the most straightforward problem to solve. All you have to do is to figure out how much water is needed for your cucumber plants. Let’s have a look at it.

Make sure you are not overwatering your cucumber plant. It decreases oxygen level, which as a result, makes your cucumber leaves turn yellow. Your cucumber leaves need only 1 or 2 inches of water once a week, including the rainfall. In case of drainage problem, lose your cucumber plant soil by mixing it with sand. Another way is to grow your cucumber plant into raised beds or containers with big drainage holes. If you want to learn more, read in-depth guides like this.

You can also use gadgets to measure the moisture in your soil. It will prevent you from overwatering or less watering your cucumber plants. Doing this simple step wrong can make your cucumber leaves yellow.

Nutritional deficiencies:

Cucumber needs different nutrients. When they lack any nutrients, chlorophyll occurs. To check your plant lacks which nutrients, it is best to get your plant soil tested in the local lab. The good news is! Suppose your cucumber leaves turn yellow because of a lack of nutrients. In that case, nutrient supplement fertilizers can help your plants retain their nutrients back. You can also easily buy these nutritional fertilizers online or from your local garden center at quite reasonable prices. Here are the common nutritional deficiencies that are turning your cucumber leaves yellow:


Excess nitrogen, zinc, and magnesium can cause iron deficiency in the soil. Iron deficiency is immobile, and the symptoms first appear in the youngest plants. If the young leaves have grown with yellow spots, then they are having iron deficiency. You can either treat the plant or treat the soil. You can also treat them both but balance is the key here. To overcome this deficiency, you have to mix powdered chelated iron into the soil or spray watered iron directly on the plant.


Potassium deficiencies are due to excess nitrogen, sodium, or calcium. So you need to fertilize your cucumber plant with the proper nutrients in a balanced amount. Cucumber is the only plant that needs potassium more than nitrogen. Potassium deficiency symptoms are why leaves become yellow on the edges, and new plates are so small, wrinkled, unfresh, and the cucumber plant is club-shaped. Using a good fertilizer can fulfill its deficiency. 


Nitrogen is one of the essential nutrients for any plant’s growth. It helps in the growth of leaves and maintains their green color. The deficiency of it not only turns your cucumber leaves yellow but also stunts their growth. As a result, they eventually die. Fortunately, nitrogen deficiency is straightforward to fix. To fulfill the nitrogen deficiency, add two-inch of compost into the soil. Or you can add 1 to 2tablespoons of 6-10-10 fertilizer per hill after one week of blossoming. This supplement should be applied then, after three weeks. 

Don’t apply the fertilizer directly to your plant’s roots; instead, use it between the rows or mounds. Be sure not to mix too much fertilizer into the soil as it will prevent your plant’s production. Be cautious not to destroy the roots by being gentle during the application. Don’t overuse the fertilizer, as it may stunt growth and production.

A pro tip: buy soil fertilizers that use the proper dilute rate. Even a little mash-up here can ruin your cucumber plant, and only organic fertilizers work best.
Why are my cucumber leaves turning yellow


To identify zinc deficiency, check out if your cucumber leaves turn yellow in the veins, if the new leaves are so small, and their growth is restricted.

To solve this problem, spray with the zinc fertilizer solution. You can also use organic kelp as an alternative.


If the leaves are deep yellow or bronze, your cucumber leaves are lacking phosphorous. The best way to ensure that phosphorous deficiency does not occur is to amend the soil with compost before planting cucumbers, but if you didn’t, don’t worry. You can also amend your plant now by adding one tablespoon of phosphorous fertilizer per pot.

Don’t apply fertilizer directly to your plant’s leaves or roots; instead, mix the fertilizer with the soil and then use it between the rows.


It is the essential nutrient for cucumbers because they maintain the natural green color of cucumber leaves. If your cucumber leaves are turning yellow, it might be because of a lack of magnesium. There are plenty of good magnesium fertilizers that are readily available online or in your local garden centers.

Plant insects:

You may have heard about plant insects but might not know that they all juices out of plants. They are the common reason for leaves discoloration. Some common pests that love to feed cucumber leaves are Aphides, spider mites, and whiteflies.


They are the small insects in the oval form which hang inside the cucumber leaves. Aphids are mostly yellow or green. They hide behind the sticky substance, which is called honeydew. Spray with readymade insecticide spray. One treatment weekly or bi-weekly is needed. Read the insecticidal spray label entirely before using the product. Do not spray insecticides during high temperatures.

Spider mites:

Spider mites feed plant juices, which turn plants into pale yellow, green, and brown colors. Spray water or insecticidal soaps to get rid of spider mites.


Whiteflies are the white-winged tiny insects that sit behind your plant’s leaves and fly away when they get disturbed. Remove leaves that get affected because of whiteflies and are now turned.

Yellow also; remove the whole plant if it got affected.

Potato leafhopper:

They are crazy plant juice suckers. While feeding in your plants, they leave a toxin on the leaves, which makes them turn yellow, and then the leaves eventually fall.

Using Insecticides is an easy and tempting option to kill them instantly, but it is not healthy for the human body. The alternative option is to clear all the weeds and cover your plants with row covers.

The University of California integrated statewide pests management recommends cultural control for potato leafhoppers instead of insecticides.

Squash bugs:

Squash bugs are brownish or black color bugs in the flat shield-like form with the triangle at their back. They feed the juice of cucumber leaves that turn plants into yellow, brown, And black color and then rot. Trap the squash bugs into the cardboard, through them away, or kill. You can also spray them with water .pressure


If your cucumber leaves have yellow spots, it means that they are suffering from some plant disease. To find out exactly what this disease is, you will have to explore more, but there is no treatment for any illnesses, so your cucumber plant may die. It’s better to remove the area of a plant that got affected by the disease so it may not spread widely. Avoid planting crops belonging to the cucurbit family, such as melons or squash, for several years because the condition will affect the next crop.

If you find out white powdery spots on your cucumber leaves, this might be because of fungus disease or no watering. Have a look to find out common diseases that turn cucumber leaves into yellow color.

Fusarium wilt:

Are your cucumber leaves turning yellow started from the corners and now moving forward?

A cucumber beetle larva is the cause of this because they eat plant roots. Just like the mosaic virus, the only solution to this is to cut out the affected area. There are also other ways to prevent this fungal disease.

Verticillium wilt: 

Verticillium wilt is commonly caused by planting cucumber on where you have previously grown other vegetables, such as tomatoes, potatoes, eggplants, and peppers.

Cucumber mosaic virus:

Is your cucumber leaves wrinkled with yellow spots and now turning downward? The possible reason for this might be that they get affected by the cucumber mosaic virus.

Unluckily, there is no treatment available. The only way to tackle this is to cut down the yellowish, wrinkled part of your plant. Not doing so will spread widely carried by plant pests such as aphids and potato leafhoppers. Be cautious because it can affect new plants in the coming year. 

Downy Mildew:

Downy Mildew disease causes a yellow spot on the top of your cucumber leaves which later turn into brown color. Also, in extreme humidity, gray fuzz is found inside the leaves. Here are the several options to overcome this disease:

  1. Planting those varieties of cucumber plants that have high resistance.
  2. Increase space between rows to improve irrigation and air circulation.
  3. Remove the infected plants as soon as possible to control spread. 
  4. Systemic fungicides and contacts are effective for downy mildew if applied at the early stage of the disease.
Why are my cucumber leaves turning yellow


Doing gardening and harvesting your plants is very rewarding, but nothing hurts more than a dead plant when you are gardening. Educating yourself to know its cause and finding the solution is helpful for yourself and your garden. Whether you use modern gadgets or gardening in old ways, there is nothing more rewarding for a gardener than a growing, productive, and harvest-ready plant.

In this article, we have discussed all the possible causes of why cucumber leaves turn yellow and also provided the solution for each problem. Let us know in the comment below if you found this article helpful. What is the issue that you found matching with the causes mentioned above? Also, if you want to add any helpful information, you are more than welcome to do so; we would love to hear from you

Happy gardening!

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