Why are my cucumber leaves turning yellow are a sun-loving vegetable, but when they don’t get enough light, their leaves may turn yellow. This condition, known as chlorosis, can result from lack of sunlight, overwatering, or other factors. To help cucumber plants thrive, place them in an area that gets six to eight hours of sunshine a day and remove nearby plants that block or decrease the amount of sunlight they receive.

If your cucumber plant’s whole foliage turns yellow but the veins remain green, it’s likely a sign of an iron deficiency. You can solve this problem by spraying the plant with liquid iron or using chelated iron in powdered or granular form. Alternatively, you can use a soil test to determine what nutrients are lacking and amend the soil with fertilizer that contains those ingredients. Cucumbers also require a higher amount of potassium as they flower, so you should reapply a fertilizer that contains this element.

Green Woes: Understanding and Resolving Yellowing Cucumber Leaves

Another common cause of yellowing cucumber leaves is fusarium wilt, which begins with the bottom leaves and gradually moves upwards. The yellowing is caused by a disease from the verticillium fungus, and it’s best to remove infected plants and prevent their spread. This fungus can be spread by aphids and leafhoppers, so be sure to check them often and remove any you find.

Downy mildew is a fungal disease that can make cucumber plants look yellow and spotted with gray mold. It’s a serious plant disease that can kill cucumbers, so gardeners should take steps to prevent it. Choosing resistant varieties, spacing plants better, and boosting air circulation are all good ways to reduce the risk of downy mildew. You can also use a systemic or contact fungicide to treat cucumbers that have already started to yellow or are showing symptoms of this disease.