Using a few tricks, gardeners may change the color of their blue hydrangea blossoms to pink or reddish-purple, but it is not always possible to create the exact shade of purple you may want. Creating a deep shade of purple or red may be very difficult, if not impossible, for gardeners growing hydrangea flowers in very warm climates. You can’t change white hydrangea flowers, so start with blue or pink varieties if you want to change the color of the blooms.
Difficulty: Moderately Challenging
Plant hydrangeas that will never turn blue. Certain types of hydrangea will produce richly-colored blossoms that will look purple or vividly pink. Choose Alpegluhen and Kardinal if you want your flowers to stay pink or purple in tone.
Test the pH of the soil using a kit found in home and garden stores. If the soil is below 6.0, it is likely the flowers will appear blue instead of pink.
Add fertilizers containing dolomitic lime and phosphorus to raise the soil pH up to 6.0 to 6.2. When hydrangeas appear blue instead of purple, it’s an indication that the soil is high in aluminum. Lime and phosphorus help reduce the aluminum levels to create the purple color you want.
Apply fertilizer several times a year until the soil reaches the pH level you want. Add fertilizer every four to six weeks in spring and summer to raise the pH.
Test the soil pH again one to two weeks after applying fertilizer to monitor your soil’s progress as it moves toward the right level. Soil pH that is too high may damage hydrangea flowers or prevent proper growth.
Grow hydrangeas in pots to exercise more control over the soil. It is easier to turn hydrangea flowers purple when you have the ability to change the soil at will.