How To Prevent Cucumber Leaves From Turning Yellow?

Having cucumber plants in the garden is a great help in the kitchen. They are not that high-maintenance and just require a few conditions which they probably share in common with your other garden plants.

Here’s how to prevent cucumber leaves from turning yellow:

  1. Adequate sunlight for 6-8 hours daily
  2. Porous soil with 1 to 2 inches of water per week
  3. Check and treat plants with pests immediately 
  4. Provide adequate nutrient levels with fertilizer (especially Nitrogen and Potassium)
  5. Eradicate diseased plants and dispose of them well
  6. Use metal and toxin-free water sources 

Just keep your cucumbers happy and you won’t have to deal with yellow leaves. Read on to find out what causes yellow cucumber leaves and how you can avoid it. 

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Possible Reasons Why Your Cucumber Leaves Are Yellowing

There are a number of reasons why your cucumber plant leaves are turning yellow. Some of the reasons are easy enough to rectify others though like pests and diseases might get worse before getting better. 

The cause of the yellowing leaves include:

  • Too much or too little light
  • Overwatering or underwatering
  • Pests that affect cucumber plants
  • Diseases that affect cucumber plants
  • Lack of nutrients (particularly Nitrogen and Potassium)
  • Water with a high mineral or metal presence 

We shall go through these reasons and offer you solutions as to what to do.

#1- Light

Too much light can make the leaves of your cucumber plant turn yellow. But so can too little light. Be they indoor or located outdoors these plants need the right amount of sunlight if their leaves are to remain green and alive! 

Cucumber leaves need anywhere between 6 to 8 hours of direct sunlight every day! Note that six to eight hours of indirect sunlight cannot be a complete replacement for direct sunlight. 

When a cucumber plant’s total sunlight exposure falls below the 6 hours mark, leaves turning yellow won’t be surprising! 

Do This

Carefully decide where to situate your cucumber plant! If they are positioned in a greenhouse make sure you position them where they will receive direct sun for 6 or 8 hours daily. If you are unable to meet this requirement then invest in a grow light. 

You could also use an LED grow light if the plant is indoors or in an enclosed greenhouse.

Otherwise outside a greenhouse, they should not be put under a canopy that offers more shade than sun. Consider allowing your cucumber to have longer hours in the sun if the sunlight available is weak.

If you have too much sunlight, consider giving the plant shade for the latter half of the day. 

#2- Watering

When it comes to watering, just like a lower or higher amount of sun can be damaging, the same applies to water. 

Give your plant the right amount of water to keep them happy. Giving too little water is just as much a problem as giving too much. Sometimes it’s best to just insert your finger 2 to 3 inches into the soil and feel if the soil is moist or dry.

Remember by overwatering the cucumber plant you are suffocating the roots of oxygen and providing bacteria with an easy entrance. Excessive water will result in cucumber leaves turning yellow. 

But underwatering also results in diminished health of your plant, the first signs are again yellow leaves. Your cucumber plant needs 1 to 2 inches of water per week, not any less!

Do This

You can prevent cucumber leaves from turning yellow due to improper watering by establishing a proper watering cycle from day one! 

If you are watering your cucumber plant adequately but water is still accumulating, it could be a drainage problem. To improve drainage, grow your cucumber on raised mounds. Or, add porous materials to your soil, this could be anything from sand to perlite.

So what If you don’t have Perlite, check out these 15 Perlite Alternatives. 

When growing in a pot, ensure the pot has enough drainage holes. For pot-growing, you can use a soil tester to check moisture in the soil. But, doing the finger test for moisture, as we have described above is the best option to ensure proper watering.

#3- Cucumber Plant Pests

If your cucumber plant is located outside it may be that it has fallen prey to one or many pests. The pests may be small and hard to detect and until you know what you are looking for, you may miss them.


Aphids are a pest that you should guard against as their constant sap feeding can cause cucumber leaves from turning yellow. When in extremely high populations, aphids are a big problem to deal with. These extremely small insects are usually white and appear under the leaf or at the midrib. 

Spider Mites

Again these small red insects feed on the sap of your cucumber leaves. Excessive feeding can lead cucumber leaves to turn yellow. The presence of webs on cucumber leaves in addition to discoloration is a sure sign of spider mites. 

Do This  

Managing pests depends on catching them early and taking preventive measures to avoid cucumber leaves turning yellow due to excessive loss of leaf sap. 

  • As soon as you notice specks on the underside of leaves or at the midrib, observe them to determine if they are in fact pests. 
  • Treat your cucumber leaves with a soapy solution 
  • Apply horticultural neem oil to your plants to hinder the pest’s ability to grasp the leaf’s surface. 

#4- Lack of Nutrients 

Providing adequate nutrients is the first step to preventing cucumber leaves from turning yellow. All plants have more or less the same nutrient type requirements. However, nutrient quantity requirements differ from plant to plant. 

Cucumber leaves turning yellow due to nutrient deficiencies can be grouped into two types: Macronutrient deficiencies and Micronutrient deficiencies.

Macronutrient Deficiencies

This includes nutrients that are crucial for plant growth and health and which are necessary in high amounts. Examples are Nitrogen, Phosphorus, and Potassium. 

Micronutrient Deficiency 

Micronutrients are required for optimal plant health but they are only required in very small amounts. Examples are Zinc, Iron, Manganese, Copper 

Failure to satisfy your cucumber’s nutrient requirements will lead to yellowing of leaves, chlorosis, and yellowing leaf tips, edges, or veins. Eventually, the leaves will change color and they will die leaving an unappealing sight! 

Do This

Use a nutrient test kit to evaluate your soil’s nutrient profile. Based on these results and your cucumber’s requirements, you will have to fertilize your plants or provide organic materials that can replenish nutrient levels. 

Most nutrient deficiencies are solved by adding the appropriate fertilizer or spraying with a nutrient solution to facilitate faster uptake of the nutrient. 

Other solutions include improving soil pH or moisture to remove the plant’s ability to absorb the nutrient. This is usually the case when the nutrient levels are adequate yet the plant is having problems taking in the nutrient. 

NOTE- Potassium (K) and Nitrogen (N) are two nutrients cucumber plants are greedy for. Ensure their levels are always adequately high. 

#5- Cucumber Diseases

Another overlooked way to prevent cucumber leaves from turning yellow includes keeping an eye on cucumber plant diseases. The majority of cucumber diseases are transmitted through soil, water, or air. The causative agents are bacteria, fungi, or viruses. 

Cucumber diseases that can cause yellowing of leaves and their control are as follows. 

  • Downy Mildew

This disease is common in a range of vegetables and flowering plants. Downy mildew is a highly destructive disease brought about by a water mold. Starting off as just yellow spots, gray mold develops on the underside of leaves which later turns brown. 

Humid and cool conditions favor the rapid proliferation of Downy Mildew.

  • Mosaic Virus

Mosaic virus is another problem affecting over 150 types of plants including fruit trees, vegetables, and even flowering plants. The presence of this virus is characterized by mottled green and yellow leaves. The virus remains viable in the soil and once plants are infected transmission is possible through leafhoppers and aphids. 

No treatment exists for the mosaic virus, there are a few ways to prevent it from infecting your plants!

  • Fusarium Wilt

Caused by the fungus Fusarium oxysporum, Fusarium wilt exhibits symptoms similar to Verticillium wilt. Symptoms include dropping, yellowing, and stunting of lower leaves. 

Fusarium wilt thrives in hot temperatures with moist soil with 30℃ (86℉) being the temperature optimal for root infection. 

Do This

Most of the diseases affecting cucumber share the same prevention methods. These tips also apply to several other vegetables and plants that are infected by the same diseases as cucumbers. 

  • Observe your plants regularly and remove infected material immediately and dispose of it properly (burying far away from plants or burning)
  • Rotate plants in specific spots of land to ensure there is a gap in the cycle
  • Use high-quality seeds or plants to propagate 
  • Ensure adequate air circulation and sunlight heat exposure to dry off excess moisture. Do this by increasing spacing between plants
  • Choose irrigation methods that don’t leave cucumber plant foliage wet
  • The use of fungicides can slow the infection of some diseases but not all 
  • Remove weeds regularly to avoid possible spread to your cucumber plants 

#6- Water Quality 

If you want to go out of your way to prevent cucumber leaves from turning yellow, you can go ahead and have your water tested. The presence of heavy metals, toxic compounds, and excessive mineral quantities can be a cause of yellowing cucumber leaves.

People don’t really pay much attention to water quality which is what makes it a factor you shouldn’t take for granted. We often think tap water or water from an open water body is safe. However, only a water test kit and be judge how safe water actually is. 

Do This

Avoid using questionable water sources or water from a river that has a factory in proximity. Using a water test kit, test your water for mineral levels and for the presence of metals.

Water with high chlorine levels can be left open as this helps to easily lower the chlorine levels without much effort. Using rainwater is another option available to ensure good water quality. If all other growth conditions are fine you should suspect the quality of water. 


The best way to ensure yellow cucumber leaves don’t lead to a dead cucumber plant is to prevent cucumber leaves from turning yellow. To keep your cucumber’s leaves green and healthy, just make sure you are providing the right environment and resources to the plants. 

  • Provide enough sunlight to your cucumber plant
  • Water your plants regularly  
  • Stay alert and check your plant regularly for pests
  • Maintain nutrient levels and avoid Nitrogen and Potassium depletion
  • Keep infected and diseases material away from your cucumber plants
  • Test water to ensure it is toxin-free and minerals are within limits

If all these conditions are available to your cucumber, you can effectively prevent cucumber leaves from turning yellow. Because once they become yellow, they don’t turn green again! 

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Should I cut yellow leaves off the cucumber plant?

If you notice the leaves of your cucumber plant are mostly yellow, you can cut them off as there are no chances of yellow leaves becoming green again! Also, doing this can help to reroute energy and resources from the dying leaves to other parts of the plant where it is needed. Your cucumber plant then has a chance of growing green leaves once conditions are improved and the plant is in better health. 

How to treat yellow cucumber leaves

Before you can get your cucumber plant to grow green leaves to replace the yellow ones, you have to identify the ‘root of the problem’. Additionally, it could be one of many reasons such as over/underwatering, lack of nutrients, or just poor environmental conditions that induce disease.