There are several reasons why your hydrangea leaves turn yellow and the good news is that most of these issues are easy to fix. Some of the most common causes include overwatering, too much direct sunlight, improper soil pH, and nutrient deficiencies.
Overwatering yellow hydrangea leaves cause them to get water-logged and suffocate, which makes it difficult for them to take up nutrients from the soil. To avoid this problem, make sure the soil is not constantly wet and provide it with adequate drainage.
Another common reason for yellow hydrangea leaves is that the plant is suffering from a lack of nutrients, especially nitrogen. Nitrogen is essential for hydrangeas to grow large, green leaves. A deficiency of this nutrient is typically the result of poor soil quality, and can be remedied by adding organic matter such as compost or well-rotted manure to the garden bed. A nitrogen-rich fertilizer that contains kelp and fish meal is also an excellent choice to help fight the nitrogen deficiency issue.
Yellow Hydrangea Leaves: Diagnosing and Treating Common Garden Problems
If the leaves of your hydrangea are yellow but the veins remain green, this is a sign that the plant is lacking iron. This nutrient is important for chlorophyll production during photosynthesis, so a deficiency of it can lead to the discoloration of the leaves, known as iron chlorosis. Iron deficiency can be corrected by using a liquid iron solution or applying a soluble powder. A foliar spray containing iron chelates is also an excellent way to replenish the hydrangea’s supply of this vital nutrient.