Why Are My Cucumber Leaves Turning Yellow?

Last Updated 7/2/2022

I remember the first time I saw yellow foliage ​on my cucumber ​plants. The cucumbers ​were freely climbing, clinging, flowering and giving a bounty of ​fruit on ​trellis I built.

​​It baffled me and caused me to ask Why are my cucumber leaves turning yellow?

​You will ​learn some of the common causes of cucumber leaves turning yellow and some solutions that ​I rapidly employ to fix things.

What is The Cause For Leaves Turni​ng Yellow

The most common reason why cucumber plants ​turn yellow, is because moisture stress has set in or a nitrogen deficiency. 

Surprisingly, ​cucumber leaves turning yellow can be caused by over watering or not watering your plants with enough water. The very first thing you should check is the container or pot you planted your cucumber plants in.

​Simply add more water to your cucumber plants if turning yellow.

​The problem is that your cucumber plants ​are not getting the right amount of water.

Make sure you water the cucumber plants ​​at regular intervals.

​Don’t forget though that too much water or over watering can also cause the yellowing of the ​plants.

If over watering of your cucumber plants is your problem then you just have to reduce the amount of water you put in the pot or the soil. You can add the right amount of water or water you plants less often.

Your nitrogen deficiency can usually be cured with some addition of nitrogen to the soil for your plants.

Plant Diseases

In many cases, diseases of the plants are often the cause for ​cucumber's leaves turning yellow. You should make sure your cucumber plants are not infested with these diseases:

Cucumber Mosaic Virus

Cucumber's leaves ​are wrinkled and curving downwards with yellow spots dotting the leaf surface.  The plants could also have evolved to have brown spots as it progresses. 

The cucumber mosaic virus may have arrived on your plants.

The virus is ​​not treatable and the only option is to remove the infected plants from the garden. If you leave the plants in the garden the virus will most likely spread by aphids and leaf hoppers.

You should be aware that the virus is able to live in the soil and infect new plants the year after.

Fusarium Wilt

This next virus is similar to the above and usually develops on the older leaves & plants. If ​your cucumbers are all turning yellow beginning from the edges towards the center of the leaf, your plant is infected with the Fusarium.

The only way to deal with this problem is also to get rid of the infected plants like the Mosaic wilt and there are options of how to go about it.

The verticillium wilt is another similar fungus that favors areas once used for growing vegetables such as potatoes, peppers, tomatoes, eggplants & a few other plants.

Downy Mildew

The presence of ​the downy mildew virus on your plants is betrayed by leaves turning yellow with spots. ​

The spots are usually present on the upper surface of leaves ​and later turns brown.

The leaf veins bind these yellow spots at an angle giving the impression of a patchwork.

It shows itself well during high humidity appearing on the underside of the leaves of your cucumbers & plants.

Treatment of Plant Diseases:

• Planting varieties of cucumbers plants that have strong disease resistance levels
• Air circulation around cucumber plants improved and leaves kept dry with wide row spacing and use of drip irrigation.
• Immediate removal of the infected plants that turn yellow to prevent spreading of the disease & promote further growth.
• Early application of systemic and contact fungicides. Soil health is essential to prevent disease & promote growth for your ​cucumbers & plants.

Pest Issues

In addition to over watering and under watering causing the leaves of your cucumber yellow, pests are a potential issue.

The pests can ​have a disastrous effect on your cucumbers & plants.

They can also turn the leaves yellow in the following ways:

Microscopic Spider Mites

The​ spider mites literally suck the sap from the leaves of your cucumber plant.

You will know that these are responsible for attacking the leaves of your cucumbers when your cucumber leaves are populated with fine silvery webbing that is draped on the underside of your leaves.

Aphids  

These are also good at sucking the life out of the leaves of your ​cucumber plants. 

When you see your cucumber leaves develop a malformed curled downwards at the edges, you are being attacked by aphids. 

The stems and leaf backs are their favorite haunts and they mass in scores partaking in their favorite meal of sprouting new growth. As the feed, they excrete a cover of clear, mushy honeydew.

Whiteflies

• Use insecticidal soap on the leaves of your cucumbers.
• Spray your plants with a suitable solution until it  is dripping from the leaves and reapply the treatment again in line with the recommended frequency of spraying your plant shown on the packet label.
• Row Covers are an all around solution for many pests especially at the beginning of the season.

Other Possible Causes

Water Related Yellowing

Over-watering your cu​cumbers will result in the depletion of oxygen around the root zone with the typical sign of leaf yellowing and wilting. 

With rainfall cucumber plants need only about 1-2 inches of water per week.

Solution

• If drainage is the problem, mix sand with the soil to loosen it up. 
• Alternatively you can plant your cucumber plants in raised beds.

Lack of Sunlight

Another cause for droopy yellow leaves on your cucumber plants could be the lack of enough sunlight.  Cucumbers need a good dose of sunlight each day.

Solution

• Move your plants to a site to get a minimum of 6 hours sunlight every day.

Final Thoughts

​Taking proper care of your cucumber plants is a must if you wish to have a bounty of cucumbers come harvest time for yourself and family.

There may be many obstacles that confront you from doing this but there are also solutions that you can use to achieve your goals that’ll help you never to shout and ask: Why are my cucumber leaves turning Yellow.