5 Reasons Cucumber Leaves Turn Yellow and how to fix it?

Are you finding yellow patches on your cucumber leaves? If so, don’t worry; yellow spots on cucumber leaves are actually more common than you think, and there are appropriate solutions in place for the problem. 

cucumber leaves with yellow spots on them.

What do yellow spots on cucumber leaves mean? 

There are normally five reasons why your cucumber leaves turn yellow; these include: 

  • Deficiencies of nutrients in the soil.
  • Cucumber plants diseases
  • Pests
  • Inadequate Sunlight
  • Watering Issue 

Like almost every other plant related issue, once you figure out the problem causing it, you should take the steps to solve the issues as soon as possible.

Why Are My Cucumber Leaves Turning Yellow?

Nutrient Deficiency in The Soil

A vital part of ensuring your plants grow healthy is making sure that the soil they grow in is full of nutrients. To make sure you’re providing such an environment to your plants, you should conduct a soil test. A soil test will figure out what your soil is missing and consequently causing the yellow spots. Once you know the problem, a simple fertilizer geared with the missing nutrients will fix your problem. 

Your plant can have different kinds of deficiencies. For example:

If your plant has an iron deficiency: the cucumber plant will have new yellow leaves with green veins. You can fix this by scattering granular iron on the sides of the roots of the plant, or you can also spray foliage using a liquid iron on the plant. 

If your plant has a potassium deficiency: your cucumber plant might get yellow leaves. This usually happens because cucumber plants specifically need higher levels of potassium when they start to grow. To fix this, you just have to use a balanced fertilizer.

If your plant has a nitrogen deficiency: the leaves of your plants will turn yellow, and if not taken care of, the plant might even die. You can use fertilizer to solve the problem; however, take care of the amount you add, as even too much fertilizer can be harmful to a plant. 

Cucumber Plant Diseases

Cucumber plants, like any other plants, can be susceptible to diseases. These include: 

Cucumber Mosaic Virus: if your cucumber plant has flecking, mottling, and mosaic patterns, it is infected with the cucumber mosaic virus. You’ll have to take the entire plant out and get rid of all roots infected with the virus to solve the problem.

Fusarium Wilt: caused by a fungus; you can recognize this disease if your plant starts to dampen off and yellow. It can cause your plant to die off in a maximum of 5 days. The disease can infect your plant anytime, and to treat it; you’ll just have to remove the infected plant entirely. 


A lot of pests like to feed on (or, more specifically, the sap of) cucumber plants. These pests include aphids, whiteflies, and spider mites. You can get rid of them by using insecticides (remember to use them in moderation). 

In fact, even the worst pest for cucumber leaves, Potato Leafhoppers, can be treated quite simply with insecticides or through the growth of other beneficial insects such as lacewings, minute pirate bugs, or ladybugs who eat leafhoppers. 

Water Issues

Yellow cucumber leaves can also be caused by water issues. If you’re inconsistent in your watering schedule, your cucumber can end up with yellow leaves. If you want your cucumber to grow green and healthy, you must make sure to supply them with at least 1 or 2 inches of water every week. 

Also, you must try to plant your cucumber plant in an area with good drainage. If you do so, your cucumber plants will thrive, and your yellow leaves won’t be caused by water issues at the very least. 

Inadequate Sunlight

Most land plants love the sun, and this goes for cucumbers too. If you plant them in a space where they don’t receive enough sunlight, cucumber leaves can turn yellow and might even wilt. Although cucumbers who get 8 hours of sunlight a day or more tend to do a lot better, you should try to plant them in an area where they get lots of it for at least 6 hours a day.