Why Hydrangea Color Changes
After you have decided that you want to make your hydrangea change color, it is important to understand why hydrangea color can change. The color of a hydrangea flower depends on the chemical makeup of the soil it is planted in. If the soil is high in aluminum and has a low pH, the hydrangea flower will be blue. If the soil has either a high pH or is low on aluminum, the hydrangea flower color will be pink. In order to make a hydrangea change color, you have to change the chemical composition of the soil it grows in.
How to Make Hydrangea Change Color to Blue
More often than not, people are looking for information on how to change color of hydrangea flowers from pink to blue. If your hydrangea flowers are pink and you want them to be blue, you have one of two issues to fix. Either your soil is lacking in aluminum or your soil’s pH is too high and the plant can’t take up the aluminum that is in the soil. Before starting a blue hydrangea color soil treatment, have your soil around the hydrangea tested. The results of this test will determine what your next steps will be. If the pH is above 6.0, then the soil has a pH that is too high and you need to lower it (also known as making it more acidic). Lower the pH around the hydrangea bush by either spraying the ground with a weak vinegar solution or using a high acid fertilizer, like those made for azaleas and rhododendron. Remember that you need to adjust the soil where all the roots are. This will be about 1 to 2 feet (30 to 60 cm.) beyond the edge of the plant all the way into the base of the plant. If the test comes back that there is not enough aluminum, then you need to do a hydrangea color soil treatment that consists of adding aluminum to the soil. You can add aluminum sulfate to the soil but do so in small amounts through the season, as this can burn the roots.
How to Change Color of Hydrangea to Pink
If you would like to change your hydrangea from blue to pink, you have a more difficult task ahead of you but it is not impossible. The reason that turning a hydrangea pink is more difficult is there is no way to take the aluminum out of the soil. The only thing you can do is try to raise the pH of the soil to a level where the hydrangea bush can no longer take in the aluminum. You can raise the pH of the soil by adding lime or a high phosphorus fertilizer to the soil over the area where the hydrangea plant’s roots are. Remember that this will be at least 1 to 2 feet (30 to 60 cm.) outside the edges of the plant all the way into the base. This treatment may need to be done repeated to get the hydrangea flowers to turn pink and once they do turn pink, you will need to continue doing this hydrangea color soil treatment every year for as long as you want pink hydrangea flowers.
