Bailey's Color Me Blue
Bonide's and Bailey's Color Me Blue is a soil sulfur that changes the acidic level of your soil, changing big-leaf hydrangea (Hydrangea macrophylla) into a blue color. Color Me Blue's sulphur pellets will make the soil acidic with a pH value below 6.0. The amount needed to change hydrangeas to a blue color depends on your soil's pH level. Use a soil tester before beginning.
Results may vary, depending on the time of year, soil type and temperature. It may require multiple applications in a season.
Note: Some hydrangea varieties (including PeeGee, Oakleaf and Annabelle) will not respond to they change in the pH value, thereby changing the bloom color.