Changing Hydrangea Flower Color: Blue vs. Pink vs. White Varieties

Critical Distinction: Species Determines Color Response

• Hydrangea arborescens ('Annabelle') & H. quercifolia ('Snow Queen'): White only—cannot change color regardless of soil pH.
• Hydrangea macrophylla (mophead/lacecap): Color shifts with soil pH and aluminum availability.

Turning Pink → Blue (Macrophylla Only)

1. Lower pH to 5.0–5.5: Apply elemental sulfur (2–4 lbs/100 sq ft) or aluminum sulfate (1 lb/100 sq ft) in spring. Water in.
2. Ensure aluminum present: Most soils have enough; aluminum sulfate supplies both Al and acidity.
3. Maintain: Mulch with pine bark, oak leaves, or peat moss. Re-test pH annually.

Turning Blue → Pink

Raise pH to 6.5–7.0 with lime (calcium carbonate). High pH locks up aluminum.

Timeline

Color change takes 1–2 seasons. Treat early spring before bud set.

If your hydrangeas are white varieties, no soil amendment will make them blue.