Maintaining Pink Hydrangea Flowers Through Soil pH Management

Hydrangea macrophylla flower color shifts from pink to blue as soil pH drops and aluminum becomes available. To maintain pink flowers in Georgia's naturally acidic soils requires active pH management.

Target Soil Chemistry

• Pink flowers: pH 6.0-6.5 (aluminum unavailable)
• Blue flowers: pH 5.0-5.5 (aluminum soluble and absorbed)
• Purple/lavender: pH 5.5-6.0 (intermediate aluminum uptake)

Management Program

1. Soil test: Through county extension — essential for precise amendment rates.
2. Apply lime: Dolomitic lime (calcium magnesium carbonate) at test-recommended rate to raise pH.
3. Incorporate phosphorus: Superphosphate or bone meal helps bind aluminum.
4. Mulch with alkaline materials: Crushed shells, hardwood ash (sparingly).
5. Retest annually: Soil naturally re-acidifies; maintenance is ongoing.

Important Caveats

• White hydrangea cultivars cannot be colored — they lack pigment genes.
• Container plants are easier to control than in-ground plantings.
• Excessive lime causes nutrient deficiencies (iron chlorosis).

Consistent soil testing and targeted liming maintain the pink coloration this gardener prefers.