The right color hydrangea is very personal to those of us who care about hydrangeas (I am one of those who loves hydrangea!) I had always heard that coffee grounds sprinkled around my hydrangeas will change the color of hydrangea blooms, making them the dramatic blue many gardeners covet. The truth is more complicated, according to a soil scientist. I decided to explore the better ways to change my hydrangea blooms from blue to pink or pink to blue – and share it with you!
Changing Hydrangea Bloom Colors
You can change the flower colors of some bigleaf hydrangeas and mountain hydrangeas by altering the pH of the soil in which they are growing. Soil pH acts as a gatekeeper for aluminum, a common element found in most soils. Acidic soil, with a pH of 6.0 or lower, makes aluminum more readily available to hydrangeas, causing the blooms to turn blue. Alkaline soil, with a pH of 7.0 or higher, prevents aluminum absorption, resulting in blooms that are pink or red. For true blue hydrangeas, the plants need to be grown in acidic soil with a pH of 5.5 or lower. For pink flowers, the plants need neutral to alkaline soils (pH 6.5 and higher). For purple blooms (or a mix of blue and pink flowers on the same plant), the pH of the soil must be between pH 5.5 and 6.5. Your soil test results will help you figure out what to do next.
Adjust the Soil pH
Most garden soils tend to be neutral, so you’ll need to amp up the acidity to go blue. You can do that in a variety of ways. Organic acidifiers include sulfur and sulfate. There are also easy-to-use soil additives made specifically for hydrangeas. Bailey’s Color Me Blue (soil sulfur) or Bailey’s Color Me Pink (garden lime) change the pH of the soil so you can enjoy the hydrangea bloom color you want. These all-natural products make the soil more acidic (for blue hydrangeas) or alkaline (for pink). Add the pelleted mixture to the soil when you plant your hydrangea.
Mississippi State University (MSU) Extension recommends applying 1 cup of dolomitic lime per 10 square feet or ½ cup of sulfur per 10 square feet to hydrangea plants in the fall to alter their bloom color by the following spring. MSU Extension also recommends using a soil drench of 1 tablespoon of aluminum sulfate per gallon of water to turn hydrangeas blue or 1 tablespoon of lime per gallon of water to turn hydrangea flowers pink. Apply the soil drench to the base of the bush once a month for three months in the spring or early summer.
Choose Blue Hydrangea Varieties
Look for hydrangeas that are bred to be blue such as ‘Nikko Blue’, Endless Summer The Original, ‘Penny Mac’, ‘Blauer Prinz’, or Endless Summer Twist-n-Shout. The photo on the plant tag will help you choose blue-blooming varieties if the plants aren’t in flower at the nursery.
ABOUT THE AUTHOR
Lise Howe is an Associate Broker with RLAH @properties and has been helping buyers and sellers throughout Bethesda, Chevy Chase, Montgomery County, and Washington, DC for nearly 40 years. Known for her warm, personalized approach and deep knowledge of the local market, Lise believes that every client deserves honest advice, clear communication, and an advocate who genuinely cares about their goals.
Whether working with first-time buyers, downsizers, or luxury home clients, Lise combines decades of experience with a commitment to making every real estate transaction as smooth and enjoyable as possible. When she’s not helping clients, you’ll often find her walking the Capital Crescent Trail with Captain, exploring local neighborhoods, or sharing insights about the communities she loves.