Changing Hydrangea Flower Colors: From Pink to Blue and Back

The old saying "lime makes 'em pink, sulfur makes 'em blue" holds true for French hydrangeas (Hydrangea macrophylla). Soil pH directly affects flower color by controlling aluminum availability.

How Soil Chemistry Works

Acidic soils (low pH) make aluminum more available, resulting in blue flowers. Alkaline soils (high pH) lock up aluminum, turning flowers pink. Most soils naturally acidify over time, so hydrangeas tend toward blue unless amended.

Turning Blue to Pink

Apply 1 cup of garden lime around the plant each year. Over two to three years, the blue will gradually shift to pink. Repeat annually to maintain the color.

Turning Pink to Blue

Mix 2 tablespoons of aluminum sulfate per gallon of water. Drench small shrubs (3' x 3') with 1 gallon yearly; larger shrubs can take 2–3 gallons. Apply in early spring for best results.

Note: A few cultivars are genetically pink and won't change color regardless of soil treatment.