While growing cucumbers indoors, it can be struggled to see cucumber leaves turning yellow. As we all know a healthy and vigorous cucumber plant should have green foliage, we may wonder why my cucumber leaves are turning yellow? In the very essence, cucumber leaves turn yellow because of the loss or decrease of chlorophyll - a pigment that aids cucumbers in the green color.
To expand, the major cause of chlorophyll lack is Nitrogen deficiency. Besides, pest infection and overwatering are also primary leads. In the following content, we’ll explore the 3 major factors that cause cucumber leaves to turn yellow. Additionally, we'll offer practical solutions to help your cucumber plants thrive.
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[Reasons & Fixes] Why Are My Cucumber Leaves Turning Yellow?
There are 3 major reasons why my cucumber leaves turning yellow, which include soil nutrient deficiency, overwatering cucumbter, and pests and diseases. Keep reading and figure out solutions accordingly.
Soil Nutrient Deficiency (Especially Nitrogen)
Like many other home-grown plants, cucumber plants require a balanced diet of nutrients, say, nitrogen, potassium, and phosphorus. When encountered with yellowing leaves, you should have a particular emphasis on nitrogen intake.
As one of the three primary macronutrients, Nitrogen takes charge of the synthesis of chlorophyll, the green pigment in plants. Without sufficient Nitrogen, your cucumber leaves are highly likely to turn yellow. Plus, chlorophyll is essential for photosynthesis.
Downy Mildew Cucumber Leaves Turning Yellow
Later, as cucumbers develop into the flowering stage, you should pay attention to magnesium deficiency in cucumbers. With insufficient magnesium, the leaf veins usually stay green, but the areas between them turn yellow, a condition known as interveinal chlorosis.
To prevent from Nutrient Deficiency
First thing first, ensure your cucumber plants receive a balanced fertilizer containing nitrogen, potassium, and phosphorus. Once you see the signs of yellowing leaves, take action and re-consider the nutrient proportion. For example, you may want to add more nitrogen-driven fertilizer during the vegetative stage and supply enough magnesium during the flowering stage.
Overwatering
If the soil nutrient is nothing wrong after checking, how about your watering routine? Did you massively water your cucumber lately? If so, overwatering can cause cucumber leaves to turn yellow.
Overwatering Cucumber Leaves
When soil is constantly saturated, the roots of the cucumber plant can become deprived of oxygen, leading to root rot. Damaged or rotted roots are less effective at transporting nutrients to the plant, resulting in nutrient deficiencies we mention above. What’s worse, overwatered soil can lead to a leaching effect, where essential nutrients like nitrogen are washed away from the root zone. So basically, it’s still the lack of nutrients that leads to yellowing cucumber leaves.
To avoid overwatering cucumber plants
- Before watering your cucumber plants, assess the soil's moisture level by gently inserting your index finger or thumb into the soil, about 1-2 inches deep near the base of the plant. If it feels moist, there’s no rush to water the soil yet.
- While watering, do it in the morning, if possible. This allows the foliage to dry out smoothly during the day, reducing the risk of fungal diseases that thrive in moist conditions. Also, water deeply and thoroughly to ensure the water penetrates the soil to reach the root system.
Pests and Diseases
One more major cause of cucumber leaves turning yellow is pest infection. When certain pests feed on cucumber leaves, they can disrupt the normal functioning of the plant and lead to a variety of symptoms, including yellowing of the cucumber leaves. Let’s see what are they.
Cucumber Leaves Suffer from Pests and Diseases
Aphids
Aphids excrete a sugary substance called honeydew as they feed plant sap. This honeydew can encourage the growth of sooty mold on the leaves, which can block sunlight and inhibit photosynthesis. Reduced photosynthesis then leads to yellowing leaves due to a lack of chlorophyll production.
What’s worse, one mottled discoloration virus named cucumber mosaic virus(CMV) often takes cucumber as the host. Once aphids feed on plants infected with CMV, they ingest the virus particles along with the whole plant sap. CMV can then multiply and replicate within the body of the aphid, circulating and reproducing within the aphid's system.
Spider Mites
Spider mites are tiny arachnids that feed on plant cells by piercing them and sucking out the contents. Their feeding process can damage plant cells and disrupt the flow of nutrients and water within the plant, therefore, leading to cucumber plants turning yellow.
Additionally, cucumber plants are likely to be attacked by the following pests:
- Whiteflies
- Leaf Miners
- Cucumber Beetle Larvae
- Cabbage loopers
- Cutworms
- Slugs and snails
- Thrips
To recover yellowing leaves from pest infection:
Unfortunately, cucumber plants are not likely to recover from pest infections. The only remedy you can do is to remove the infected parts as soon as possible before the infection spreads to the whole plant.
- First, identify the specific pest responsible for the infestation. If you are not sure about the species, take a picture of the pests and leave a comment below! We’d like to help.
- Carefully inspect the plant for yellowing and damaged leaves. Prune and remove these affected leaves from the plant.
To prevent pest diseases in the future, you can implement appropriate pest control measures to eliminate or manage the infestation, such as:
- Handpicking
- Insecticidal Soap
- Chemical Pesticides
[Reasons & Fixes] Why Cucumbers Are Light Green?
Cucumbers are light green due to the presence of chlorophyll in their skin, which is the pigment responsible for the green color in plants. Compared to darker green vegetables, the light green shade of cucumbers, is influenced by several factors. These include the specific variety of cucumber, the amount of sunlight the plant receives, and the thickness of the cucumber skin. Cucumbers typically have a higher water content and thinner skin, which can result in a lighter green appearance as opposed to deeper green vegetables which have more chlorophyll and thicker skins.
Cucumbers Are Light Green
To deepen the green color of light green cucumbers, ensure the plants are getting adequate sunlight exposure, apply a balanced, nutrient-rich fertilizer to the soil to promote chlorophyll production, and maintain consistent soil moisture to avoid water stress. Also, you should consider choosing cucumber cultivars that are naturally a darker, richer green color rather than waxed, store-bought varieties. By addressing these key factors related to light, nutrients, and water, you can help encourage the development of more vibrant, deep green coloration in your homegrown cucumbers.
How to Treat Yellowing Cucumber Leaves?
Seeing yellowing leaves on your cucumber plants can be alarming, especially when you're eagerly awaiting a bountiful harvest. But don't panic! While yellowing leaves can indicate various issues, understanding the causes and implementing the right treatments can help you revive your plants and get them back on track.
Having figuring out the common reasons behind cucumber leaves turning yellow, we'll offer you some treatment tips in this regard:
- Improve Soil Health: Add compost or organic matter to enhance soil structure and nutrient availability.
- Proper Watering: Water at the base of the plant, not overhead, to reduce disease risk. Ensure consistent moisture, especially during flowering and fruiting.
- Fertilization: Use a balanced fertilizer according to the plant’s growth stage. For quick nutrient uptake, consider foliar feeding.
- Pest Control: Regularly inspect leaves for pests and treat early. Encourage beneficial insects like ladybugs in your garden.
- Disease Management: Space plants properly to ensure good air circulation. Remove any diseased leaves immediately and use appropriate fungicides if needed.
What to Do If Yellow Spots on Cucumber Leaves
Instead of entire leaves turning yellow, sometimes you may notice yellow spots on cucumber leaves. In that case, the cucumbers are possibly experiencing downy mildew, a type of fungal disease.
Yellow Spots on Cucumber Leaves
Downy mildew often happens in cool, wet, and humid conditions and rapidly spreads across the plant once it takes hold. Leaves affected by downy mildew typically display yellow patches with distinct edges. If you take a closer inspection beneath the leaves, you’ll see a dark purple mildew – this is where the spores form and disperse.
How to Fix Downy Mildew on Cucumber Plants
Similar to pest infections, there’s no way to fix or cure the fungal-affected cucumber plants. It’s also suggested to get rid of the spotted leaves as soon as possible, just in case of a bigger spread. However, there are indeed some precautions you can take. For example, space plants further apart to enhance air circulation.
For climbing cucumbers, maintain a distance of 12-18 inches between each plant. For those growing directly on the soil, a spacing of 36 inches or more is preferable, though it's not the most efficient approach.
Should I Cut Off Yellow Cucumber Leaves
It depends on the cause. If your cucumber leaves turn yellow because of nutrient deficiency and overwatering, there’s no need to cut off all yellow leaves. As long as you take remedies, they stand a chance to turn green again. However, if your plant leaves suffer from pest infection or downy mildew, you should cut off yellow cucumber leaves before the virus takes over the whole plant.
Conclusion
Cucumber leaves turning yellow indicates the plant lacks the green pigment, chlorophyll. Insufficient nutrient supply, overwatering, and pest infection are the three major causes of the absence of chlorophyll in your cucumber plants. Hopefully, by following the solutions offered above, you can fix yellowing leaves on cucumber plants and enjoy a fruitful harvest.
My cucumber and watermelon plants are suffering from yellowing leaves and holes on the leaves. Any help would be great. They’re still producing right now.
Hi Nickie,
If there are holes spreading and the leaves are yellowing, my instinct hunt is the pest. Flip the leaves over and check what’s behind, maybe you’ll find out something.
There is also angular leaf spot which is a bacterial disease affecting cucumbers, zucchini, melons, etc. On mine it started out as yellow spots on the leaves. There were no pests and fertilizing didn’t help. Four plants were producing 4 huge salad cucumbers and about 20 pickling cucumbers a week. And then yellowing leaves and fruit production has slowed to nothing. It turns out my husband sprayed down the plants with rainwater treated with bacteria (we have a large underground tank that gets stinky). Before that all watering was done by a soaker hose.
Hi Anthony,
Thanks for sharing this! We’ll considier adding this to the post, thanks for your tip!
Would you help me diagnose my problem with our cucumbers? The end of the leaves look green and healthy, except for some holes from pets. Not sure if there’s anything you could recommend to spray and keep the pests off or if it’s too late. Some leaves are yellow and have lots of holes so I cut them off. I have lots of flowering but I’m afraid I’ll lose my crop if I don’t do something. I can send pics.
Hi Amber,
It sounds like your cucumber is ruined by the pests. To fix that, you can use organic insecticidal soap or neem oil spray to deter pests. Make sure to spray under the leaves as well.
For severe situations, apply a fungicide specifically designed for cucumbers such as copper-based fungicides. However, it’s possible that these fixes fail to save your plants because it’s too late.
I have burplus cucumber plants. Many of the leaves are having yellow round spots all over them. I have a spray bottle filled with water and have a teaspoon of olive oil infused with vinegar and several drops or dawn liquid soap in it. Looking at leaves underneath a magnifying glass I can’t see any evidence of red mites or any bugs on the leaves. I live in Houston Texas and I use about a gallon of water per day on the 4 plants in a large clay pot. If I don’t water it by mid afternoon all the leaves are wilted. I use miracle grow fertilizer that dissolves in the water and fertilizer it every other day. I’ve had 3 cucumbers so far and they are delicious!! Any idea what is causing the yellow spots? Thanks
Great information but I’m really not sure which is my problem. Can I send a picture?
We’d like to help:) Can you describe your situation?