Just So Blue

The color of French hydrangea (Hydrangea macrophylla) blooms is determined by the pH of the soil they grow in. By adjusting the pH to make it more acid, you can turn pretty pink flowers into beautiful blue ones. It’s a simple project with big rewards. Here’s what you need to know to change the bloom colors of your hydrangea from pink to blue. (White hydrangeas? Sorry, they don’t play along. They stay white regardless of the soil pH.)