Buzz
Adore your hydrangeas but curious about experimenting with their color? Certain varieties allow you to shift their hues. Here’s everything you need to know.
Color-changing hydrangeas are variety-specific
Before diving in, it’s important to note that not every hydrangea can change its color. This unique trait is found in specific Bigleaf hydrangeas (H. macrophylla), particularly Mophead and Lacecap varieties, as well as H. serrata cultivars. While pink and blue hydrangeas of these types can shift colors, white hydrangeas remain unchanged.
What causes hydrangeas to shift their color?
According to the Farmers Almanac, it’s best to wait until a hydrangea is at least two years old before trying to alter its flower color. Additionally, the color change isn’t immediate—it often takes weeks or even months to see the full transformation.
The hue of hydrangeas depends on the amount of aluminum the plant can absorb from the soil, which is influenced by the soil’s pH level.
In acidic soil (lower pH), plants absorb aluminum more easily, typically resulting in blue flowers. In alkaline soil (higher pH), aluminum absorption is limited, usually leading to pink blooms.
Steps to alter the color of hydrangeas
Start by testing your soil’s pH level and ensure you have aluminum sulfate ready. Here’s the next step:
Transforming pink hydrangea blooms into blue
To shift pink flowers to blue, boost the soil’s acidity. Achieve this by mixing 1⁄4-ounce aluminum sulfate with a gallon of water and applying it three times annually, beginning in spring.
Repeat the application every three to four weeks. When using the aluminum sulfate solution in spring, also follow the manufacturer’s guidelines to apply 25-5-30 fertilizer.
Changing blue hydrangea blooms to pink
To transition blue flowers to pink, raise the soil’s alkalinity. Achieve this by applying ground limestone (dolomitic lime) at a rate of four pounds per 100 square feet during spring or fall, ensuring it’s well-watered. Simultaneously, use 25-10-10 fertilizer as directed by the manufacturer.
Using hard water, which is rich in minerals, can also help in transforming blue hydrangea blooms into pink.
