Blue Flowered Hydrangea is Now Pink

The flowers of my hydrangea are no longer blue but pink. What does this plant need?

The blue and pink flower color is influenced by soil pH. White hydrangea flowers will be white no matter what the pH. The pH is a measure of the soil's acidity. Acid soils with a low pH, often called sour, have more available aluminum that gives the flowers a blue color. In alkaline or sweet soils (pH over 7.0) the aluminum is tied up in the soil. Changing the soil’s pH, is difficult. The easiest option is to enjoy the pink flowers. If you like a challenge, try using aluminum sulfate or an acidifying fertilizer to encourage blue blooms. Avoid late season fertilization that encourages late season growth that can be winter killed.