Since it was discovered that the flower color of the common garden hydrangea could be changed by changing soil pH, homeowners have enjoyed practicing such horticultural wizardry and impressing their friends and neighbors.
Flowers become pink in alkaline soil and blue in acid soil. To change pink flowers to blue, spread a small amount of wettable sulfur, about ¼ cup on a three-foot plant, around the plant and water it in well. Keep in mind, too much sulfur can damage the plant, so be careful.
Another way to make the flowers more vivid blue is to dissolve a teaspoon of alum in a gallon of water and drench the soil around the plant.
To change flower color from blue to pink, apply dolomitic lime around the plant at 1-2 cups for a three-foot plant.
For best results, apply the suggested treatments once in March and April as the plants are beginning to grow and again in June when the flowers or coloring. You may be disappointed in the results if you wait to late in the flowering cycle to apply the treatments.
Michael Wheeler is the Hall County extension coordinator. Phone: 770-531-6988. Fax: 770-531-3994.