Soil pH plays a critical role in the color and health of hydrangea blooms, particularly for Bigleaf hydrangeas. A pH of 5.5 or lower will produce blue flowers, while a pH of 6.0 or higher will result in pink blooms. Testing your soil pH is the first step in determining the right fertilization strategy.
You can use a soil pH test kit, available at most garden centers, to measure your soil’s acidity or alkalinity. Adjusting the pH can be done by adding lime to raise it or sulfur to lower it, but these changes should be made gradually and monitored regularly.
3. Timing Your Fertilization
Timing is everything when it comes to fertilizing hydrangeas. The best time to fertilize is in early spring, just as the plants are beginning to leaf out. This timing ensures that the nutrients are available when the plants need them most for growth and bloom production.
A second application can be made in early summer, but avoid fertilizing after August as this can encourage new growth that may not harden off before winter, leading to damage.
4. Choosing the Right Fertilizer