Hydrangea Flower Color Depends on Soil pH: Acid = Blue, Alkaline = Pink

It's All About Aluminum Availability

Hydrangea macrophylla color:

• Acid soil (pH < 5.5): Aluminum available → **blue flowers**.
• Alkaline soil (pH > 6.5): Aluminum locked up → **pink flowers**.
• In between: Purple/mauve blend.

How to Shift Color

• Blue: Add aluminum sulfate or sulfur to lower pH.
• Pink: Add lime to raise pH.
• White cultivars never change.

Resource

Hydrangea Color Change Guide – Step-by-step.

Test soil first; adjust gradually.