How do I keep my garden hydrangea blue?

Color

All hydrangeas undergo some color change as their flowers age, but only big-leaf hydrangeas can change their color in a predictable, controllable way. It is not the soil pH that is responsible for this change – it is actually the presence of aluminum in the soil that does it.

• Certain bigleaf varieties cannot experience color change – generally speaking, the more intense the color, the less likely it can change. Similarly, white varieties of big-leaf hydrangea will not change color.
• It is easier to change a hydrangea from pink to blue than from blue to pink, but both endeavors involve making chemical applications in specific amounts at specific times. A soil test is necessary to determine the best course of action. If you decide to try to change the flower color, shop for products carefully and read all directions.
• Pennies or nails in the soil will not change the flower color!