How to Turn Hydrangea Blooms Blue: Soil pH and Fertilizer Guide

Reader Question: Blue Blooms in Richmond, VA

"We live in Richmond, Virginia. What fertilizer produces blue hydrangea blooms? Ours were white this year, then turned brownish."

Expert Answer: Not All Hydrangeas Change Color

First, identify your hydrangea type. Some varieties—like 'Annabelle' (smooth hydrangea) or 'Snow Queen' (oakleaf)—are naturally white and will not change color regardless of soil pH.

Only bigleaf hydrangeas (Hydrangea macrophylla, the mophead and lacecap types) shift bloom color based on soil pH:

• Acidic soil (pH < 6.0) → blue flowers
• Alkaline soil (pH > 7.0) → pink flowers

How to Lower Soil pH for Blue Blooms

1. Elemental sulfur (garden sulfur) – Apply lightly as a fine dusting every few weeks over the growing season. Do not overapply; too much too fast can damage roots.
2. Acidifying fertilizers – Products like Miracid (30-10-10) or Espoma Holly-tone (organic) gradually lower pH while feeding.
3. Aluminum sulfate – Works faster but risks aluminum toxicity if overused; sulfur is safer for long-term adjustment.

Test soil pH before and during treatment. Aim for 5.2–5.5 for true blue.

Why Your Blooms Turned Brown

White-to-brown progression suggests either a white variety aging naturally, or heat/drought stress. Fertilizer won't fix browning caused by weather.

Key Takeaway

If you have a bigleaf hydrangea, lower soil pH with sulfur or acidifying fertilizer. If it's a white variety, enjoy the blooms as they are—no fertilizer will turn them blue.