Yellow Leaves on Hydrangea

Hydrangeas show signs of distress when their leaves turn yellow, a condition that can signal various problems. Yellow leaves often indicate that the plant is not receiving what it needs or is experiencing stress. This discoloration can reduce the plant’s ability to photosynthesize, weakening it and potentially leading to fewer blooms.

What are the 6 Main Causes of Yellow Leaves on Hydrangeas?

When a hydrangea shows yellow leaves, it means something is wrong with the plant. There are six main reasons why this might happen:

• Inadequate Light: The plant does not get enough sunlight.
• Overwatering or Dehydration: The roots are either too wet or too dry.
• Low Temperatures: The plant is too cold.
• Inadequate Soil pH: The soil is not acidic or alkaline enough for the hydrangea.
• Nutrition Deficiency: The plant isn’t getting the right nutrients it needs to stay healthy.
• Normal Ageing of Leaves: Old leaves sometimes turn yellow before they fall off.

Each reason affects the plant in a way that can be fixed if we understand how to care for hydrangeas the right way.

1. Inadequate Light

When we talk about inadequate light for hydrangeas, we mean that the plant isn’t getting enough sunlight. Hydrangeas prefer bright light, but not direct, scorching sun. They often thrive best with morning sun and afternoon shade. If a hydrangea doesn’t get enough light, it may struggle to grow properly.

Without enough sunlight, the leaves can turn yellow, the plant can become weak, and it might produce fewer blooms. To ensure a hydrangea receives adequate light, it should be placed in a spot where it can enjoy the morning light and be protected from the intense afternoon sun. 

2. Overwatering or Dehydration

Overwatering is when a hydrangea plant gets more water than it needs. Its roots can drown because they need air too. Without enough air, the roots can’t do their job well, and the plant starts to suffer. Yellow leaves may be a sign that the plant is getting too much water. On the other hand, dehydration happens when the plant doesn’t get enough water.

Like people, plants need water to stay healthy. If a hydrangea doesn’t get enough water, it can’t make food properly, and its leaves might turn yellow. It’s important to give hydrangeas just the right amount of water—not too much and not too little—to prevent the leaves from turning yellow.

3. Low Temperatures

Hydrangea plants thrive in warm environments and can become stressed by cold weather. If the temperature drops below what hydrangeas prefer, the plant may react by turning its leaves yellow. Think of it like a plant’s way of saying it is too cold. This problem is common in the fall as the weather changes or if a hydrangea is planted in a spot where it doesn’t get enough warmth from the sun.

It’s important to know the right conditions for hydrangeas to avoid low-temperature stress. For example, most hydrangeas grow best in zones 6 to 9, where the climate is milder. Therefore, if you live in a place with cold winters, you might need to protect your hydrangeas from the cold to keep them healthy.

4. Inadequate Soil pH

Soil pH measures how acidic or basic the soil is. Hydrangeas need soil with a pH that is not too far from neutral to grow well. If the soil pH is not right, their leaves can turn yellow. This happens because the wrong pH can stop plants from getting the nutrients they need from the soil.

Different kinds of hydrangeas may prefer slightly different pH levels, but most of them thrive in soil that is slightly acidic to neutral. If the soil is too acidic or too basic, gardeners must adjust it. They can add lime to raise the pH or sulfur to lower it.

Once the soil pH is corrected, the hydrangeas can absorb the right nutrients, and their leaves should start looking green and healthy again.

5. Nutrition Deficiency

Nutrition deficiency happens when a hydrangea doesn’t get the right amount of essential nutrients from the soil. Just like humans need a balanced diet to stay healthy, plants need a mix of nutrients to grow properly. If the soil lacks these nutrients, the hydrangea cannot make enough chlorophyll, which is vital for the process of turning sunlight into food, known as photosynthesis.

Without enough chlorophyll, the leaves can turn yellow. This is because chlorophyll gives leaves their green color. The nutrients most commonly lacking are nitrogen, phosphorus, and potassium, but hydrangeas also need other minerals in small amounts.

If a hydrangea does not receive these important nutrients, it will show warning signs like yellowing leaves. This condition can be fixed by adding fertilizer that contains the missing nutrients to the soil.

6. Normal Ageing of Leaves

Just like humans, hydrangea plants grow older and change over time. The leaves of hydrangeas go through a natural aging process. When leaves get old, they often turn yellow, then brown and dry before falling off the plant. This is a normal part of the plant’s life cycle.

It happens because the leaf is no longer needed by the plant and is thus not provided with the necessary nutrients to stay green. New leaves will usually grow to take their place. It’s important to know that this type of yellowing is different from the yellowing caused by problems like too much water or not enough light.

Therefore, if the yellow leaves are mostly at the bottom of the plant and the rest of the plant looks healthy, it could just mean that the leaves are simply getting old.

What is Chlorosis in Hydrangeas?

Chlorosis is when hydrangea leaves turn yellow because they can’t make enough chlorophyll. Chlorophyll is the green stuff in leaves that helps plants use sunlight to make food. Without enough chlorophyll, the plant can’t feed itself well, and its leaves might look yellow or pale.

To treat chlorosis in hydrangeas, you should:

• Check the soil’s pH because hydrangeas like it a little acidic. If the pH is too high, you can lower it using sulfur or aluminum sulfate.
• Make sure your hydrangea is getting the right nutrients, especially iron. If it’s not, you might need to add a fertilizer that has iron in it.
• Look at how much water the plant gets. Both too much and too little water can cause chlorosis, so it’s important to find a balance.

What to Do with Yellowing Hydrangea Leaves?

When the leaves on your hydrangeas turn yellow, it’s a sign they need your help. To deal with yellowing leaves, follow these steps:

• Check the amount of light your plant gets and move it if it’s too much or too little.
• Make sure you’re watering your hydrangea correctly – not too much and not too little.
• Protect your plant from cold drafts or move it to a warmer spot if it’s too cold.
• Test the soil pH and adjust it if it’s not right for hydrangeas.
• Feed your plant with the right fertilizer to prevent nutrient deficiencies.
• If a few leaves are yellow and you’re sure the plant is healthy, it might just be natural aging. In that case, you can remove the yellow leaves by trimming them off.