Why Are My Hydrangea Leaves Turning Yellow?

There are many different types of hydrangeas, and some are naturally pale-leafed, but there are no hydrangeas with naturally yellow leaves. Yellowing leaves (Chlorosis) in hydrangeas is a symptom of several different problems, including: 

  • Overwatering
  • Fungal infection
  • Underwatering
  • Compacted soil
  • Improper soil pH levels
  • Lack of iron and other nutrients
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To correctly treat your hydrangea’s yellow leaves, you must first determine the cause of the problem and then take appropriate steps to remedy the situation. In this article, we provide information to help you do just that. 

Learn details on Hydrangea plant care.

Overwatered Hydrangeas are Sure to Develop Chlorosis

In hydrangea plants, and most plants, overwatering will cause yellowing leaves. Hydrangeas like to grow in well-draining soil kept slightly moist. These plants cannot tolerate standing in water, and soggy soil will cause yellowing leaves and much more severe problems.

Soggy soil prevents the plant from breathing, so one of the first signs of trouble is yellowing leaves. If the problem is not resolved, the plant will stop growing, and fungal disease will set it. Once this happens, the plant is very likely to die.

If your plant is standing in soggy soil, withhold watering until the soil dries up. Don’t allow it to become completely dry, though. If the soil is compacted, you will need to repot your plant.

To Repot, Follow These Steps:

  • Cleanly prune away all yellow leaves using a very sharp, sterile implement.
  • Remove the plant from its container and brush or wash away all of the old soil. Examine the roots carefully. If root rot has set in, use a very sharp, sterile implement to prune away the damaged roots.

Rinse the roots thoroughly and allow the plant to air for a few hours before repotting in a completely new or completely sterilized pot with a fresh potting mixture.

  • Place the plant in a sheltered area with only 3 or 4 hours of morning sun a day. It should remain in a sheltered position until it begins to thrive again.

Should You Always Cut Off The Yellow Hydrangea Leaves?

Yes, all yellowing leaves should be pinched or clipped off. They will not turn green again, and their presence on the plant uses the energy that the plant could use to recover.

Can a Hydrangea Recover from a Fungal Infection? 

Fungal infections are difficult to treat, mainly when the fungus affects the roots. Root rot prevents plants from being able to uptake nutrients correctly. Additionally, it causes deterioration of the roots.

Powdery mildew can be a real problem on hydrangea plants. If you notice cottony, white fungal growth on the undersides of your plant’s leaves, suspect powdery mildew. This form of fungus also causes yellow spots to form on the upper sides of the leaves. Your plant may also develop a fungal infection on the leaves if the leaves stay wet and don’t have correct air circulation around them.

Excessive Sun Exposure Causes Yellow Leaves

Another cause of yellowing leaves in hydrangeas is leaf scorch. This happens from exposure to harsh, bright sunlight. If your hydrangeas’ leaves wilt and then turn yellow, your problem may be the excessive sun. You can avoid this problem by positioning your hydrangea plant in the correct light setting. Most types of hydrangeas like a partial sun setting.

Hydrangea plants need at least 3 hours of sun per day, but they can tolerate up to 6 hours of sun daily. The best sun exposure for hydrangeas is the morning sun with light shade in the afternoon. Your hydrangea plants will want to be protected from the noonday sun or the late afternoon sun as this harsh, direct light can cause leaf scorch.

Learn about the Florida Hydrangea Dombeya Seminole

Thirsty Hydrangeas Experience Chlorosis

Underwatering can also cause yellowing leaves in hydrangea plants. As with most plants, hydrangeas that do not get enough water begin to wilt, droop and turn yellow.

It’s essential to keep a regular watering schedule for your hydrangeas and be sure to water at least once a week. Water thoroughly so that the water runs through the soil and out of the pot’s drainage holes, but you don’t want it to pour out excessively.

The Wrong Soil can Cause Chlorosis

To make the best use of water, always use a light, airy, well-draining potting mix for your hydrangea plants. The correct soil will allow good air circulation and proper water retention.

The right soil for hydrangeas should include lots of organic matter such as manure. When repotting, mix in some properly aged manure to ensure that the plant receives the right amount of nutrition.

It’s also essential that soil for hydrangeas be slightly acidic. The correct pH level is between 5.5 and 6.5. If the soil is not acidic, water with a solution containing citric acid used in pickling and canning. Two-level teaspoons of citric acid per gallon of water is a safe solution. 

Too Little Iron Causes Chlorosis

A lack of iron may also cause Chlorosis. Iron chlorosis typically causes new leaves to turn yellow first. If your hydrangeas’ leaves begin to turn yellow, but the veins remain green, suspect a lack of iron.

If you have hard water, iron chlorosis is likely. Luckily, it’s easy to address this problem by simply giving your plant a good feeding of iron chelate.

If you’ve been overwatering your hydrangea, it may be suffering from both soggy roots and a lack of iron. If this is the problem, in addition to giving your plant a good feeding of iron chelate, you may need to repot it and give it entirely fresh, new, light, airy potting soil.

Too Little Nitrogen Causes Chlorosis

A lack of nitrogen may also cause Chlorosis. You can tell this apart from iron chlorosis because lack of nitrogen typically affects older leaves. You will initially see mature leaves begin to turn yellow, and then the yellowing will gradually spread. Another symptom of nitrogen chlorosis is stunted growth. 

You can resolve this problem by supplementing with nitrogen, but you must also figure out why your plant is low in nitrogen. Several different circumstances can lead to a lack of nitrogen, such as overwatering and/or lack of magnesium can.

Be sure to regularly use a good, balanced fertilizer to provide your hydrangea with all of the nutrients it needs.

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