Phlox Leaves Turning Yellow: A Sign of Trouble?

Do you have a phlox plant in your garden? If so, have you noticed that its leaves are turning yellow? This can be a sign of trouble for your plant. In this blog post, we will discuss the possible causes of this problem and how to fix it. We will also provide some tips on how to care for your phlox plant so that it stays healthy and beautiful!

Why Is My Phlox Turning Yellow?

Overwatering, fungal infections, nutrient shortages, insufficient sunshine, and environmental stressors are the most common causes of yellow leaves on a phlox plant. The exact cause of your plant’s yellowing leaves will depend on the specific conditions in which it is growing.

I will now go over each of these causes in more detail so that you can determine which is the most likely cause of your plant’s problem.

1. Overwatering

If you are watering your phlox plant too frequently, this could be the cause of its yellow leaves. When a plant is overwatered, the roots are unable to get the oxygen they need to function properly. This can lead to a number of problems, including yellow leaves.

If you think that overwatering is the cause of your plant’s yellow leaves, the first thing you should do is reduce the frequency of watering. Allow the soil to dry out completely before watering again. You may also need to adjust the amount of water you are giving your plant.

Not only does increased watering leads to oxygen deprivation in the roots, but it also encourages the growth of fungal diseases. Root rot is a common problem in plants that are overwatered.

If you think that your plant is suffering from root rot, it is important to take action immediately. Inspect the roots of your plant for signs of rot. If you see any, you will need to cut away the affected roots and replant your phlox in fresh, well-draining soil.

2. Fungal Infections

Fungal infections are another common cause of yellow leaves on phlox plants. These infections can be caused by a number of different fungi, including powdery mildew and downy mildew.

Fungal infections often occur when the conditions are wet and humid. If you live in an area with high humidity, it is important to take steps to reduce the moisture around your plant. This includes water in the morning so that the leaves have time to dry before nightfall.

You should also avoid crowding your plants. If possible, provide them with plenty of space so that air can circulate freely around them.

If your plant does develop a fungal infection, you will need to treat it with a fungicide. Be sure to follow the instructions on the label carefully. My favorite anti-fungal treatment is neem oil (Amazon link), but there are many other options available.

In addition to treating your plant with a fungicide, you should also take steps to prevent future infections. This includes keeping the area around your plant clean and free of debris. You should also remove any infected leaves from your plant as soon as you see them.

3. Nutrient Deficiencies

Nutrient deficiencies are another possible cause of yellow leaves on phlox plants. The most common nutrient deficiency in phlox plants is iron deficiency. This can be caused by a number of factors, including improper soil pH and poor drainage.

If you think that your plant’s yellow leaves are due to a nutrient deficiency, the first thing you should do is test the soil. You can purchase a soil testing kit at your local garden center or online.

Once you have determined the pH of your soil, you can take steps to adjust it if necessary. If your soil is too alkaline, you can add sulfur to lower the pH. If it is too acidic, you can add lime to raise the pH.

Fertilizer should be added to the soil in early spring. Be sure to use a fertilizer that is specifically designed for phlox plants. I recommend a balanced 10-10-10 fertilizer for most phlox plants.

4. Lack of Sunlight

Phlox plants need full sun to grow and thrive. If your plant is not getting enough sunlight, this could be the cause of its yellow leaves. You see, the green coloration in leaves is due to a pigment called chlorophyll. Chlorophyll is essential for the process of photosynthesis, which is how plants convert sunlight into energy.

If your plant isn’t getting enough sunlight, it won’t be able to produce enough chlorophyll. This can lead to a number of problems, including yellow leaves.

If you think that lack of sunlight is the problem, try moving your plant to a sunny spot. If possible, choose an area that gets at least six hours of direct sunlight per day. Make sure nothing is blocking the sun from reaching your plants, such as buildings or trees.

You can also try using grow lights to supplement the sunlight. Grow lights come in a variety of shapes and sizes, so you should be able to find one that will work for your plant.

5. Environmental Stressors

There are a number of environmental stressors that can cause yellow leaves on phlox plants. These include extreme temperatures, drought, and flooding.

If your plant is experiencing any of these stressors, it is important to take steps to mitigate the problem. For example, if your plant is in a drought-prone area, make sure to water it regularly. If it is in an area that is prone to flooding, make sure the soil drains well.

You should also take steps to protect your plant from extreme temperatures. If it is in a particularly hot or cold area, you may need to provide some type of shelters, such as a shade cloth or windbreaker.

Should I Cut Yellow Leaves off My Phlox?

There is usually no need to cut yellow leaves off your phlox plant. In most cases, the leaves will eventually fall off on their own. Pruning leaves can be a good idea if they are significantly affecting the plant’s appearance.

If you do decide to prune yellow leaves, be sure to use sharp, clean shears. This will help prevent the spread of disease. Make sure to dispose of the leaves in a trash bag so they don’t infect other plants.

Will Yellow Phlox Leaves Turn Green Again?

No, it is not common for yellow phlox leaves to turn green again. If your plant’s leaves are yellow, it is likely that they will stay that way until they fall off.

One exception to this is if the yellow leaves are due to a nutrient deficiency. In this case, you can take steps to correct the deficiency and the leaves may turn green again.

The good news is that fixing the issue should help your plant to grow new, green leaves. So find the issue, get to work on fixing it, and then be patient while your plant recover and creates green leaves again.


In conclusion, if your phlox leaves are turning yellow, it is most likely due to one of the following issues: nutrient deficiency, overwatering, fungal infections, lack of sunlight, or environmental stressors. If you can identify the problem and take steps to fix it, your plant should recover and start growing green leaves again.

If you have any questions or comments, please feel free to leave them below. I would love to hear from you!

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