As we mentioned, hydrangeas love at least slightly acidic soils. Without these conditions, the leaves will tend to turn yellow. This is a significant problem because this discoloration affects chlorophyll photosynthesis and therefore the plant's ability to grow and bloom. To remedy this, you should intervene as early as the end of winter by spreading iron sulfate on the soil weekly.
However, this is a treatment that yields few results because soils act as a buffer system and tend to return to their original pH. On the other hand, applications of chelated iron through irrigation are very effective. Even with just a few applications, you can see good and long-lasting results.
Look for products that work across a wide pH range. For emergency treatment, there are also products suitable for foliar application. Be sure to carry out treatments in the early morning hours or in the evening because the active ingredients degrade quickly when exposed to light and heat.
