If you have hydrangeas, you will face the common problem of hydrangea leaves turning yellow at some point.
Let us look at the 11 causes and possible solutions to fix them.
Causes for Hydrangea Leaves Turning Yellow
Let us look at the causes and how you can fix your Hydrangea.
One of the main causes of hydrangea leaves turning yellow is overwatering.
Hydrangea prefers well-draining soil that is moist. If the water is not draining out properly, the soil will become water-logged, as a result of which the leaves of the plant will look yellow and droopy.
Excess water makes the soil soggy, and the roots drown in the water. The plant is unable to breathe properly. This results in fungal diseases, root rot, and stunted growth of the plant.
Hydrangeas love water, but they will not grow in wet areas.
Solution for Overwatering causing Hydrangea leaves to turn yellow
The first thing you need to do is to stop watering. If the soil is very wet, let it dry out.
Different varieties of hydrangea require a different amounts of water. Generally, hydrangeas need to be watered every 5 to 10 days in dry weather and do not need to be watered at all if it is raining.
Make sure your hydrangea is planted in a pot that has good drainage. If not, drill two or three holes at the bottom of the pot so that any extra water can flow out.
The type of soil also matters. Clay soil can hold moisture for a longer time than sandy soil. Hydrangeas require well-drained but moist soil.
Underwatering, too, has the same symptoms as overwatering.
Usually, underwatering is a result of not having a fixed watering schedule. If you constantly forget to water your plants or water your hydrangea until more than a week has passed, it will lead to discoloration, wilting, and yellow leaves.
The best way to check if your hydrangea is underwatered is to check the moisture levels of the soil.
You can just stick your fingers in the soil. If your finger comes out with some soil residue stuck to it, your soil is moist and your plant is well-watered. If your finger comes out clean or with soil that gets blown away easily, your soil is dry and needs to be watered.
You need to make sure that the soil around your hydrangea plant is always moist. Adhere to a strict watering schedule so that you do not forget to water your plants.
Chlorosis is caused by a deficiency of iron and magnesium in the plant.
In this disease, the leaves of the hydrangea turn yellow, but the veins remain green. However, in the last stage of chlorosis, the veins also become yellow and the leaves start dying.
Iron is important for the creation of chlorophyll, the element that gives the plant its green color. If iron is lacking in a plant, the leaves are less green in color.
If your plant is suffering from a deficiency of iron, simply adding iron to the soil around the hydrangea is not going to work.
The soil needs to be slightly acidic for it to absorb the iron. So, you first need to check the pH of the soil. You can easily get soil testing kits at the market.
If the pH is more than 6.7, you need to acidify the soil. You can also mulch the soil with compost. Compost is an organic soil acidifier. However, it takes up to a year to work.
Once your soil has been acidified enough, you can apply iron to it in a form suitable for your plant. Iron chelate is the best option and is easily available in the market.
#4. Leaf scorch
Too much sunlight can also cause the leaves of the hydrangea to turn yellow. This is called leaf scorch.
Leaves turning yellow due to leaf scorch can be a common occurrence if your plant is placed in a place where it receives too much direct sunlight.
The amount of sunlight that a hydrangea needs depends on the variety of hydrangea. A few varieties of hydrangea prefer only partial sunlight, which means that if they are exposed to sunlight for the whole day, they will start wilting and turning yellow.
If your hydrangea gets scorched by the sun, you need to move it to a darker location.
Hydrangeas enjoy the early morning sunlight and afternoon shade. If you cannot avoid too much sunlight, you will need to water your plant more frequently. This will ensure that the plant retains some moisture.
You also need to make sure that your plant is not completely in the dark, as a lack of light will lead to a lack of flowers.
#5. Nutrient deficiency
Often, a lack of some nutrients needed for the growth of the plant can cause yellowing of the leaves.
This usually happens because of a nitrogen deficiency. When the plant is lacking nitrogen, the leaves first become pale and slowly turn yellow.
Sometimes, if the soil has a high pH, it can prevent the plant from getting nutrients. So, first, you need to check the pH of the soil. If it is more than 6.5, you need to acidify the soil.
Then, you need to feed your hydrangeas. As a flowering plant, hydrangea needs more fertilizers because flowering plants require more energy to spend on the flowers.
You can fertilize your hydrangeas twice a year, once in early spring before the plant starts blossoming, and later after flowering when the flowers have wilted.
Make sure to use a generous amount of fertilizer. The amount of fertilizer your plant needs will depend on the type and size of the plant.
Fungal infestations on plants can be contagious. They show signs on the roots and leaves of the plant, and if not taken care of immediately, can kill the plant slowly.
Fungal diseases prevent the plant from feeding properly and will result in pale or yellow leaves that start withering eventually.
Drooping yellow leaves could be a sign of root rot, a fungal disease that affects the roots of the plant.
Fungal diseases are mostly caused by high temperatures and humidity. On top of that, if there is not enough air circulation around the plant and no sunlight to get rid of the moisture, it will only increase the problem.
So, you need to move your hydrangea to a location that gets light that is sufficient for your plant.
Here are some other tips that you can follow
- Make sure there is a gap of at least one foot between the plants so that air can flow freely through the plants.
- Do not leave any plant debris around the plants, as it will rot and infest more diseases.
- Make sure to remove the infected parts of the plant and dispose of them carefully.
- If any of these solutions do not work, spray your plant with some good-quality fungicide.
Leaf spot is another disease that can cause yellowing of the leaves.
Cercospora leaf spot is a fungal disease that usually develops during the rainy season. As the leaf spot reaches the advanced stages, the leaves of the hydrangea start turning yellow.
In the beginning, you will notice small purple spots on the leaves which eventually turn grey. If left unchecked, the entire leaves will turn yellow by the end of the season.
To stop the disease from spreading, remove all the affected and fallen leaves, and dispose of them carefully.
Do not water the hydrangea from the top. Instead, water it at the base so that the leaves do not become and stay wet.
If the hydrangea continues to be affected by the disease, try using a fungicide that contains chlorothalonil.
#7. Drop-in temperature
When there is an abrupt drop in temperature, it can cause yellow spots to develop on the hydrangea leaves. Hydrangeas can tolerate the frost by preparing themselves to become dormant.
However, sudden changes in temperature, for example, sudden cold drafts, or when it is very hot in the day and very cold at night, can cause stress to the plant. Such stress can lead to the plant developing yellow patches on the leaves.
Provide your plant with the right temperature. If the forecast suggests cold, you can cover your plant with something like a garden net to protect it from the frost.
Most plants recover from temperature changes after a while. You can apply some liquid fertilizer to your plant so that it helps the plant heal faster.
#8. Root issues
Damage of any kind to the roots can result in the leaves of the hydrangea turning yellow.
Root injury will make the roots incapable of performing their activities of providing nutrients and water to the other parts of the plant properly. Thus, the plant will eventually turn yellow.
Roots can be damaged by root rot, fungal diseases, rodents or other creatures, or even as a result of transplanting.
If your roots have been damaged by transplant shock, give them one or two months to recover. Keep the plant in shade for that time. Water it regularly, but do not overwater the plant.
If the plant has been damaged by rodents or root rot, you will need to remove the affected roots after digging out the plant.
Apply some fungicide to the damaged areas. Replant the hydrangea in drained soil and shade it for a few months. Keep the soil moist but do not water it regularly.
#9. Soil pH
The leaves of hydrangea can turn yellow if the soil has low acidity.
Hydrangeas grow well in soil with a pH between 5.5 to 6.5. If your soil is alkaline, the plant may have a problem with growing properly.
You need to check the pH of the soil to make sure that the soil is the problem.
If the leaves of your plant are turning yellow because of alkaline soil, you can easily rectify the problem. To make the soil acidic, water it occasionally with a diluted solution of acetic or citric acid.
Use mulch to retain moisture in the soil.
#10. Natural yellow color
Hydrangeas typically have green leaves. However, there are some varieties of hydrangea that have yellow leaves. For example, the Lemon Daddy variety has leaves that turn yellow as the plant ages.
So, when you purchase a hydrangea, be aware of the variety you are getting. The leaves usually turn yellow during the fall season.
#11. Aging of leaves
As plants grow older and reach the end of their cycle, they do not perform their functions with the same energy. As the life process slows down, the plant slowly starts to wither.
If only the lower part of your plant has leaves that have turned yellow, there is a good chance that it is only because your plant is naturally aging.