Hydrangea Flower Color and Soil pH: The Aluminum Connection

Yes, pH Affects Color—But Only If Aluminum Is Present

• Acidic soil (pH <5.5): Aluminum soluble → blue/purple flowers.
• Neutral/alkaline (pH >6.5): Aluminum locked up → pink flowers.
• Transition zone: Purple/mauve blends.

Caveats

• White hydrangeas don't change.
• Newer cultivars (Endless Summer, etc.) are bred for color stability—less shift.
• Container plants: easier to control with aluminum sulfate (blue) or lime (pink).

Practical Tip

Test soil pH first. Adjust gradually. Results take a full season.