The Question “Why Are My Cucumber Leaves Turning Yellow?” Is Finally Answered

Every gardener, including me, had come across a situation which disrupted his plans. When it comes to gardening, you may ask yourself many questions. “Why are my cucumber leaves turning yellow?” might be the next one. Or is, at the moment.

I have been there, and because I didn’t know at the time what to do, here is this article. It will help you identify the problem, and tackle it successfully, so you may still enjoy in cucumber salad.

Why Are My Cucumber Leaves Turning Yellow


Why Bothering With Cucumbers At All?


When I was writing about remarkable plants to grow in summer, I mentioned cucumbers among others. In this text, I said that for me, cucumbers are tastier than water, and I can still say it. These green and beautiful vegetables are excellent choices for beginners, and if you haven’t developed your green thumb yet, cucumbers are great for a start.

In case that you didn’t know, here are some general facts about cucumbers:

  • The place of its origin is South Asia
  • Cucumbers are from the family of gourds. Therefore this guide can help you even with squashes or zucchini to some extent
  • The pH of the soil must be around 7.0
  • leaf
    They prefer well-manured soil
  • leaf
    Full sun is required for them to grow properly
  • leaf
    A trellis is helpful, but not essential, as is with zucchini

Causes Of The Leaves Turning Yellow

There are several reasons for this to happen, and I have covered them all. I have given my best to organize them from the easiest to check and solve to those more complicated and harder ones. In any case, the reasons are as follows.



Perhaps the most often cause to change of colors of leaves are pests. These nasty little critters are known to bug you (pun intended) for a prolonged period. In most of the cases, these pests are sucking the life-giving juice which circulates the plant, so parts of it or the plant in whole, withers and die. Also, they are very persistent and live in swarms, so eradicating them is more than often a difficult task. Here are some of the most notorious ones.



As the name suggests, whiteflies are easy to recognize. They are white, and they fly. Most often, they will spend their time sitting on the underside of the leaves. If you go through the row of cucumbers and turn a few leaves to see a cloud of tiny, white insects, those are whiteflies. They are mainly nasty because in time they tend to develop immunity to insecticides, so eradicating them might require a bit more effort.

Ladybugs and lacewings can eat through their numbers, but the situation gets more complicated when I tell you that they can have allies as well. Namely, the larvae of whiteflies are producing black-ish goo which is sticky to the touch. This goo is high in sugar and can be found on the underside of the leaves.

Also, it attracts ants, which will defend whiteflies from other bugs, since this is their food source. To exterminate the population of whiteflies, I recommend using neem oil mixed with water and a few drops of liquid soap. This mixture can be sprayed either by using hand-sprayer or a bigger one, depending on the situation.

Spider mites

Spider Mites

“Spider mite, spider mite, does whatever a spider mite does” Homer Simpson would say, and although this would be a funny thing to see in an episode of a favorite TV show, the truth is far grimmer.

At first, I thought that my cucumbers are merely “having a few spots here and there.” In fact, the time for action was already upon me; only I didn’t know that. Later, I have spotted strange webbing around my plants, but no spiders in sight. Retrospectively, when the first few spots appear, this is a call for action.

Spider mites are called like that because they are close relatives to spiders (of course!) and are known to be highly resistant to whatever you throw at them. Being 1/50 of an inch small makes them hard to spot, and even more challenging to kill manually. Therefore, use already mentioned neem oil one week, following with diatomaceous earth next, and see what happens. If they are still present (although probably in few numbers), bring in the cavalry (I keep saying that) as good old ladybugs.

Also, be careful not to kill or otherwise dispose of larvae of these helpful little guys. Here’s a picture of ladybug’s life cycle, so that you know.



We’re still in the land of small critters which eat big. The term “aphid” represents a whole family of possible intruders, but a familiar feature for all of them is that they will not stop until all that can be eaten is dealt with.

Merely the sight of millions of aphids creeping here and there makes my skin crawl. They can be seen with naked eye, and are leaving yellow or brownish spots or blotches on leaves. What’s even worse, they will not hold restraints toward flowers, stems, leaves or fruits, to them everything is food.

Therefore, they must be stopped from spreading any further. To eradicate them, there are several ways, and all are organic. Cold water is what they hate, so give them an icy shower as the first solution. Next, if they are resistant to this method, try dusting your plants with flour, once they eat it, it will hold in tracks their metabolism, and thus dying. Of course, ladybugs are of assistance here.

Potato Leafhopper

Potato Leafhopper

Don’t let the name fool you. These mini grasshoppers (they kind of look like one) may be bigger in size than mites or aphids and fewer in numbers, but the range of destruction caused by them is far more significant. They will attack vegetables, trees, and succulents, literally anything green.

They are winged insects, which are “hopping” to gain the height and fly away, and thus the name. The damage left behind them includes dead, brown and crunchy edges of leaves, and that is how they are identified. To make things worse, they don’t just suck the juice from the plant, but their saliva is toxic, and slowly kills the plant.

This is one more reason to go to the hardware store, and buy row cover with tiniest holes possible. As I said, they are bigger than the rest of these pests, so use that to your advantage. One more way includes the usage of bugs with most awesome name ever! Enter, Pirate Bugs! Shiver me timbers; these old salts will send them to Davy Jones’ locker in no time, yarrr!


Not all culprits on this list can be seen with naked eye. It would make things too uninteresting, at least. Some of the causes of cucumber crop failing are microorganisms. Bacteria, viruses or tiny fungi colonies can wreak havoc among cucumbers. 

The Mosaic Virus

The Mosaic Virus

There are several kinds of this virus, and the range of plants which can be affected is enormous. Of course, I will focus on cucumbers only. In fact, one subspecie of this virus has the name “cucumber mosaic virus” because these are its most often target, but can infect other plants as well.

As the name suggests, any change in color or texture can be the sign of virus developing. Blotches of pale color, darker shades, or even underdeveloped leaves might be the sign of the infection. Unfortunately, the cure for this virus is not found yet, and all there is left to do is to remove infected plants and dispose of them by either sealing in a bag and throwing away, or even better, burning.

Also, since the aphids and weeds are the carriers of this virus, keeping these two in check may reduce the chance of spreading. Disinfecting the seed in 10% bleach solution is also preventive measurement, as well as purifying of the tools.

Verticillium Wilt

Verticillium Wilt

Although the mosaic virus is a real menace and can obliterate an entire harvest, fungi are not far behind by the damage they can cause. Verticillium wilt is one of the most famous fungi and can attack more than 350 kinds of trees, fruits, and vegetables.
Lighter shades of brown seen on stems are specific clue what you are dealing with.

The probability of cucumbers being infected grows if they are planted in locations where potatoes and eggplants were. As for a solution, you can try mixing baking soda with water, and spray that solution, although this has a somewhat limited effect. 

The best course of action is prevention, and to choose where cucumbers will be planted. Of course. It is highly likely that baking soda will not be sufficient, and all it is left is to remove the plants and not to plant watermelons or other squash vegetables here the next year.

Other “wilts”

Other  Wilts

There are several kinds of wilts which can be put together, although they have different symptoms and ways to deal with them. I can differ the following:

  • Powdery mildew – this one looks like a powder, thus the name. If you spot flour-like matter, remove those leaves and cut down watering; these thrive in water.
  • Fusarium wilt – stunted plants and yellow leaves are symptoms of this fungus. It attacks circulatory system of the plant, and unfortunately, it is resistant to fungicides. Remove the plants and destroy them.
  • Downy mildew – leaves brown surfaces on the upper side of leaves. It is also a fungus, but at least you can clean up the garden; any debris will make it thrive.

Feeding And Watering

Feeding And Watering

In case that none of these causes are what made the leaves of your cucumbers yellow, you can breathe out. All that is left are factors which you can solve pretty quickly.

The lack of nitrogen can cause cucumbers to gain yellowish tint, especially the leaves. Of course, fertilizer will be required, and I recommend to try either 6:10:10 fertilizer, or 33:0:0. Be careful though, that too much of fertilizer can cause burns and to be equally harmful to the plant. A tablespoon for each plant will suffice.

Also, do not forget that cucumbers are rather thirsty plants. If watering is scarce, the leaves will first suffer, becoming yellow and gravitate toward the ground. If the soil is hard and dense around the plant, try to break it a bit with a trowel. Be careful not to damage the roots. On the other hand, too much water can cause the root to rot; reduce the watering a bit, or try watering slightly further from the plant.

At The End

So, the question “Why are my cucumber leaves turning yellow?” is therefore answered. In case that even after intervention the problem persists, I know that I would call an expert to see what is the matter. This is also what I can advise to your as well

As always, feel free to share experience, tips, and questions in the comment section below.

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