Many people find themselves asking, “How can I change the color of my hydrangeas?” Hydrangeas are fascinating because, unlike most other plants, the color of their flowers can change dramatically.
It is much easier to change a hydrangea from pink to blue than viceversa. Changing a hydrangea from pink to blue involves adding aluminum to the soil. Changing from blue to pink means removing aluminum from the soil.
If you’ve decided to change your hydrangea’s color, the first step is changing the soil’s pH. The best way to determine soil’s Ph is to do a soil test. Once you get your soil test results, you’ll know whether you need to increase or reduce the Ph. Add chalk (lime) to your soil to increase the pH level, and sulfur if you want to reduce it.
Turning Pink (from Blue)
In order to do this, grow your Hydrangea in a container and make the soil’s pH alkaline by adding lime (calcium hydroxide). Your product should have instructions for correct application.
This will stop the plant’s ability to absorb any aluminum inside the potting soil. Because of the lack of aluminum, the color will turn to pink.
Turning Blue (from Pink)
A soil with a pH lower than 6.0 will normally give you blue lavender flowers. When the pH is above 7.0 (alkaline), flowers turn pink or red. If you have a pink Hydrangea and you want to turn it blue, you need to bring those pH levels down. You can do this by adding sulfur or aluminum sulfate to the potting soil.
If the blooms are currently pink, that means your soil is naturally alkaline. You can turn them blue by adjusting the soil, making it acidic. Add about 4 tablespoons of aluminum sulfate to a gallon of water and water your Hydrangea with this solution every 2 to 4 weeks.