Fixing Pink Hydrangeas: Aluminum Sulfate for Blue Flowers

Fixing Pink Hydrangeas: Aluminum Sulfate for Blue Flowers

A gardener's 2-year-old hydrangea blooms pink despite adding Miracid (acid fertilizer) per directions. They want blue/purple flowers.

The Missing Ingredient

Acid alone (Miracid) lowers pH but doesn't provide aluminum, which is essential for blue pigment (delphinidin) formation. You need aluminum sulfate.

Application

• Buy aluminum sulfate (clear 2-lb bags at garden centers).
• Apply every 2 weeks during growing season.
• Color change takes ~3 weeks.

Pruning Reminder

Only prune dead wood in late spring. Fall pruning removes flower buds on old-wood bloomers.

Consistent aluminum sulfate + acid soil = blue flowers.