How To Stop Cucumber Leaves From Turning Yellow

When growing cucumbers, you will need to give them the proper environment to thrive for you to enjoy. Unfortunately, there are several reasons why a cucumber may not do so, and the leaves may turn yellow.

Here are some ways to stop your cucumber leave from turning yellow:

  1. Provide the adequate growth needs of your cucumber plant.
  2. Test the soil to measure the levels of nutrients and iron.
  3. Give your cucumber plants the right amount of hydration.
  4. Place your cucumber plants in optimal spots for full sun.
  5. Keep the pests away and treat plant diseases.

While it may not be a serious issue sometimes, yellowing leaves may be a cause for alarm for new gardeners. In this article, you will learn about how to stop cucumber leaves from turning yellow. 

1. Provide the Adequate Growth Needs of Your Cucumber Plant

Cucumbers are reasonably easy to grow. However, they also have some specific needs to help them grow their best. If they don’t receive adequate care, cucumber plants tend to show signs, such as the yellowing of their leaves.

They Need Sufficient Space to Grow

Cucumber plants are vines and typically need room to grow unless you grow a variety designed for pots or a dwarf variety. 

Standard cucumber plants can spread over 4 to 6 feet (1.2 – 1.8 meter) and should be spaced about 4 to 5 feet (1.2 – 1.5 meter) apart when planting. It would be best to read the information on your seed packets for the ideal spacing for your variety.

Seeds can be started indoors in individual pots ten to fourteen days before transplanting them outside. Or, you can directly sow seeds outdoors when the soil is at least 70 °F (21.1 °C). Seeds should be covered with about 1 inch (2.54 cm) of soil.

Seedlings will appear in about one week, and once they are 2 inches (5.08 cm) high, they should be thinned to give proper spacing for growth.

For these seedlings to become strong and healthy plants, they need proper care. I recommend planting different varieties of cucumber plants so you can choose which ones will grow best in your garden.

Here a few common varieties:

  • Boston pickling: This plant offers continuous and high-yielding cucumbers that grow to about 3 inches (7.62 cm) long with black spines.
  • Lemon: This cucumber bears a visual resemblance to a lemon but does not taste like citrus! It offers a mild and sweet flavor with a cool and crispy texture.
  • Spacemaster: This cucumber is ideal for growing in areas where space is limited and can also thrive in pots and hanging baskets. This cucumber is slender and dark green, about 7 ½ inches (19.05 cm) long. This variety tastes excellent in salads or plain as a snack. It also is resistant to diseases such as mosaic virus and scab.
  • Straight eight veggie seeds: This variety is excellent for slicing since it grows straight. This cucumber plant heavily yields and has a sweet yet mild taste.
  • Armenian: Botanically, this variety is a muskmelon in the same family as cucumbers. It looks and tastes like a longer version of cucumber with crisp and mildly sweet flesh. These are easy to grow and are heat tolerant. 

These non-GMO seeds are harvested and packaged in the US and can be grown in a garden, trellis, vertical gardening, container gardens, and greenhouses.

Sun Exposure and Soil Quality

Cucumbers grow best in full-sun exposure and soil with good drainage. To avoid disease and promote productivity, check your garden drainage and soil composition.

Cucumbers will also appreciate compost and organic matter to improve the soil structure and grow more edible vegetation. 

Poor drainage and improper environment and nutrition can all contribute to the yellowing of leaves. 

As you read on, this article will address these issues separately to help you know how to care for and stop cucumber leaves from turning yellow.

2. Test the Soil To Measure the Levels of Nutrients and Iron

Soil deficiencies are a significant contributor to why plants struggle to thrive. Cucumbers feed heavily to grow healthy and therefore need healthy soil. 

First, you can test your soil to see why the cucumber leaves are turning yellow. To do this, you can do the following:

  1. Contact your local gardening store or county extension about soil testing. They will be able to direct you in how and where you can send in a sample.
  2. Generally, dig down about 4 to 6 inches (10.16 – 15.24 cm) around the perimeter of the cucumber plant and bring up moist samples. Collect the samples in a bucket until you have about a ½ pint (47.31 mL).
  3. Submit your sample and wait for your results. These results will tell you about the balance of your soil and what your cucumber plants may need.

Results of Soil Testing

Once you have your results from soil testing, you can take note of a few things. 

pH level

Look at the pH level. This measures acidity in the soil, with 7 representing neutral. 

Numbers below 7 show the soil is acidic. Most plants, including cucumbers, like an acidity level somewhere between 6.0 and 6.8. A number over 7 means the soil is alkaline. 

Balanced soil will also help your cucumber plants to utilize fertilizer well. Your soil report will give recommendations on improving the quality of your soil. Lime can increase the pH, and sulfur can decrease it. Both are available at your local garden center or online.


Next to note on the report from the soil testing is the nutrients. Essential nutrients that all plants need are Nitrogen (N), Phosphorus (P), and Potassium (K), also known as NPK.


Nitrogen promotes growth, especially leaves, vibrant color, and increases production yields. A lack of nitrogen can contribute to the yellowing of leaves. 

The amount of nitrogen in the soil can change quickly, so soil results may not present the whole picture. However, having a number on your report can help you make a reasonable estimate on how much nitrogen to add. You don’t want too much since it can be bad for nearby waterways.


Phosphorus is responsible for transferring energy at the cellular level for healthy blooms and produce. Phosphorus helps to strengthen stems and root systems. A lack of phosphorus will result in poor growth and poor yields. 

Too much phosphorus could be from using too much compost or manure around the plants. And too much could mean that this too will impact algae growth in nearby waterways.


Potassium is an essential nutrient for balancing fluids and electrolytes, which results in deep root systems and aids in photosynthesis. 

A lack of potassium can also result in the yellowing of leaves. 

For general nutrition, consider adding a 5-10-10 water-soluble fertilizer when planting your cucumber seeds. These numbers will be shown on the fertilizer bag and represent the ratio of NPK. It means five parts nitrogen for every ten parts phosphorus and ten parts potassium. Ensure you follow all application and safety instructions on the product’s label.


Soil tests can also examine iron, zinc, manganese, sulfur, copper, and boron levels. In particular, an iron deficiency can cause your cucumber plant to have yellow leaves but with green veins. 

This deficiency can be resolved by spraying the leaves directly with liquid iron. Be sure to follow the directions to mix the liquid iron with water and then apply to the plant. If you prefer a granular application to sprinkle around the plant’s roots instead, you can opt for iron granules.

If your soil test shows that nutrients, iron, and pH are not the issue, then other things will need to be examined. 

3. Give Your Cucumber Plants the Right Amount of Hydration

Cucumber plants need adequate water since the cucumber itself is mostly water. Mulching can help localize water for the plants’ use and control weeds. However, it is important to have the proper hydration balance for your cucumber plants since too much water is also detrimental and can cause your cucumber plants to turn yellow.

Testing Soil Drainage

To check that your soil has proper hydration for your cucumber plants, you can test the drainage. All you need is a shovel, bucket, a timer, and a water source, and then try these strategies:

Squeeze the Soil

Although cucumbers can generally grow on various types of soil, you have to ensure that the substrate in your garden has good drainage.

To check, scoop up a handful of moist soil from around the plant (or where you plan to plant seeds) and squeeze it.

Here are some characteristics of various soil types:

  • Clay soil is heavy and slippery. It is mainly due to high water retention. Too much clay in the soil composition may be bad for your cucumber plants due to poor drainage.
  • Sandy soil will quickly fall apart. This quality makes it drain water very quickly before your cucumber plants can absorb it. As a result, you may need to water your plant more frequently.
  • Loam, a fertile soil mixture of clay, sand, and humus, will hold together but fall apart if squeezed. This mixture with humus is ideal for retaining moisture and nutrients in the soil. It is also the best substrate for cucumber plants.

Checking for Moisture

If you are uncertain about when to water your cucumber plants, you can dig into the soil to see how much moisture is left. 

Normally, a dry upper layer of soil is not going to cause much trouble for your plant. A cucumber plant has a taproot system that extends three to four feet (0.9 – 1.2 m) below the surface. Therefore, it can absorb water deep into the ground.

However, if there are plenty of other trees and plants competing for the same water and nutrients, your cucumber plants may not receive enough moisture.

To ensure there is enough water for your cucumber, dig around the base of the plant using a hand shovel. Knowing that it has a taproot system should help you avoid hitting and accidentally cutting through the roots.

Dig up to a foot (30 cm) deep and feel the soil for moisture. If it is dry, it is time to add more water. Overall, this method is troublesome and is recommended only during the early stages of planting. 

You can also use a moisture meter to get a reliable reading.

Hydration Tips

In addition to mulching and adding organic materials to adjust the soil, you will want to keep in mind the overall composition of your soil after testing the hydration. 

Add water to clay soil slowly so that it soaks in deeply, but do not water again until you are sure you need more. For sandy soil, add water for less time, but you will need to do it more often.

In general, you can keep the soil consistently moist by adding an inch or two of water each week. Also consider the weather conditions, such as when the last rainfall was. If you do not water enough or consistently, your resulting cucumbers may become oddly shaped or taste poorly, and the leaves may turn yellow.

Using a drip irrigation soaker hose or a soaker hose can help keep the cucumber’s leaves drier to reduce the likelihood of water-related leaf diseases.

4. Place Your Cucumber Plants in Optimal Spots for Full Sun

Cucumbers are considered tropical vegetables and love hot weather and lots of sunlight. Before planting your cucumber seeds or seedlings, take note of your garden layout. Also, refer to the packing of your cucumber seeds for information about your specific type or variety. 

Typically, cucumbers need six to eight hours of full sunlight daily. If they do not, then their leaves will turn yellow. Additionally, too much shade combined with cucumber’s watering needs might invite unwanted slugs, snails, and other pests, which can also harm your plants.

If you need to transplant your cucumbers to an area with more sunlight, check out this helpful video on YouTube: 

However, keep in mind that the more mature your cucumber plants are, the more difficult it is to move them because their root system will be more well-established. Next year, you may have better success by planting them in a different sunny spot from the start.

5. Keep the Pests Away and Treat Plant Diseases

Cucumber plants can be afflicted by insect pests and diseases that can damage the plant and turn the leaves yellow.


Pests that may hurt your cucumber plants include the striped or spotted cucumber beetle, aphids, slugs, and potato leafhoppers. 

Here’s how they can damage your cucumber plants:

  • Cucumber beetles will chew holes in both leaves and flowers while spreading disease to the cucumber plant. 
  • Aphids will colonize the leaves and buds.
  • Slugs like the cucumber itself. 
  • Potato leafhoppers eat leaves and inject watery saliva that damages them by turning them yellow and making them eventually fall off.

Some gardeners will use a pesticide or insecticidal soap to control these, and others will use a floating row cover. Floating row covers provide a chemical-free way to keep those pests off your plants and protect them from frost. Keep in mind that these row covers may affect the amount of sunlight coming in, holding moisture in the soil.

You can also plant naturally pest-repellent companion plants next to your cucumbers. Some examples include Rosemaries, Citronella, and Lavenders. They can repel pests and add some aesthetic appeal to your garden.


Various plant diseases are problematic for cucumbers. Let’s read on to see what they are and how to treat them. 

Bacterial Wilt

The cucumber beetle will cause bacterial wilt, so managing the potential infection with the pest deterrent strategies mentioned above. Keeping your hydration needs in mind, you can use a layer of straw mulch to keep away slugs and those pesky cucumber beetles.

Powdery Mildew

Powdery mildew is created when plants are too close together. This disease leaves white patches on the leaves. If the plant is wet from watering, dew, or rain, you should avoid harvesting or handling the vines to reduce the spread of this disease. 

So, when planting, ensure you provide adequate space to discourage this from happening. If it does, you may need to thin out some plants for the others to thrive. Also, make sure you get rid of weeds to increase air circulation. 

You can keep the leaves dry using drip irrigation or use fungicides. At the end of your gardening season, clean out your beds to reduce the chances of fungus and other diseases to harbor in. 

Consider making an antifungal spray for use once a week by combining 1-Tablespoon of baking soda, 1-teaspoon of dormant oil, and 1-teaspoon of insecticidal soap with 1-gallon (4.54-liters) of water.

Cucumber Mosaic Virus

Another disease that can afflict cucumbers is the cucumber mosaic virus spread by aphids, resulting in the removal of the entire plant and surrounding weeds. This virus can live in the soil and infect future crops as well.

Fusarium Wilt

Fusarium wilt comes from a fungus called Fusarium oxysporum which can stay in your soil for a long time. It is one of the most destructive diseases cucumbers can get as the plant will typically die within a week once infected.

This disease affects the plant’s vascular system and will cause it to wilt. You will also notice an uneven yellowing on several leaves. 

Diagnosing the condition and confirming it is due to fusarium wilt is necessary to prevent spread to other nearby or future cucumber plants.

Downy Mildew

If you see yellow spots on your plant’s leaves, it could have downy mildew caused by a pathogen called Pseudoperonospora cubensis. This pathogen thrives in humid and wet conditions, so proper hydration is essential. 

This disease cannot survive on plant debris. Certain cucumber varieties have a higher resistance to this kind of mildew. When planting, cucumbers should be spaced out for good air circulation to stay dry. Fungicides can also treat downy mildew, or you can remove infected plants.

Key Takeaways

By ensuring that you set your plants up for successful growing, you will avoid cucumber leaves from turning yellow. You can do this by implementing the following:

  • Feed your plants the right amount of nitrogen, phosphorus, potassium (NPK), and iron, especially if the soil is deficient.
  • Give your cucumber plants the right amount of hydration.
  • Place your cucumber plants in optimal spots to soak up the sunlight.
  • Keep the pests away and treat plant diseases.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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