How to Change the Color of Hydrangeas

Changing Hydrangeas to Pink or Blue

By The Old Farmer's Almanac
April 23, 2020
Hydrangeas Blue and Pink

Can you change the colors of hydrangea flowers? It depends on your type of hydrangea and your soil pH. We’ll explain how to change color from blue to pink or from pink to blue.

Which Hydrangeas Can Change Color?

It’s not every hydrangea that changes color. It’s the flowers of some Bigleaf hydrangeas (H. macrophylla)—especially Mophead and Lacecap types—and H. serrata cultivars whose colors change based on the pH of the soil.

Blues are best grown in acidic soil; pinks and reds do best in alkaline or neutral soil. In other words, acidic soils with a pH of less than 5.5 produce blue flowers; soils with a pH greater than 5.5 produce pink flowers.

White hydrangea color is not affected by the soil pH. The white flowers stay white (color can never be changed) and usually prefer the same conditions as the pinks and reds.

But the relationship between color and pH is more complex than just numbers on a scale. It is the availability of aluminum ions—and the degree to which a particular cultivar can absorb them—that influences color.


How Long Does the Color Change Take?

It is possible to change colors, but not instantaneously. Color correction takes weeks—even months—for the desired changes. It is easier to change blue flowers to pink than to change pink flowers to blue, and some  cultivars are more prone to color variability than others.

We recommend waiting until the plant is at least 2 years old to give it time to recover from the shock of its original planting.

Have your soil tested for pH, then check with your local nursery for the recommended amount of aluminum sulfate and directions. Here are a few guidelines to follow, once you’ve given a plant time to recover from the shock of its original planting:

How to Change Hydrangea Color

Knowing all of the above, it’s fairly simple to increase acidity (for blue) or alkalinity (for pink):

To Go Blue

To increase acidity (for deeper-blue flowers): Apply a solution of 1⁄4 ounce aluminum sulfate per gallon of water three times per year. (Aluminum sulfate is a colorless salt obtained by the action of sulfuric acid on hydrated aluminum oxide. Buy in any garden center.) Soak the ground with the solution after the plant starts growing in the spring and repeat twice at 3- to 4-week intervals. Once a year, in the spring, apply 25-5-30 fertilizer, according to manufacturer’s instructions.


To Go Pink

To increase alkalinity (for changing blue flowers to pink): In the spring or fall, spread ground limestone (dolomitic lime) at a ratio of 4 pounds per 100 square feet and water it well. (Excessive alkalinity will cause chlorosis, or yellow leaves.) In the spring or fall, apply 25-10-10 fertilizer, according to the manufacturer’s instructions.


Other Factors

  • Hydrangea flowers will naturally fade and dry in the fall, often to a combination of pink and green or tan. This is simply the aging process, which cannot be reversed.
  • Hard water (water with a high mineral content) can also affect the flower color, turning blue flowers more pinkish, so use rainwater to water your hydrangeas, when possible.

See our Hydrangea Growing Guide for more information on planting, growing, pruning, and caring for hydrangeas!

Reader Comments

Leave a Comment

Dangers of using aluminum sulfate in your garden

It would be good if this article talked about how bad aluminum sulfate is for the environment! "Due to its acidity, aluminum sulfate significantly contaminates and pollutes areas for wild life and vegetation. As with humans, when it is mixed with water, aluminum sulfate will burn plants and animals." Google it.

Getting color in Hydrangia flowers.

I purchased a Hydrangia bush from Home Depot. It was in a plastic pot so I just transferred it to a much larger pot. The soil I used was also purchased at Home Depot. It was potting soil. However, now, all the beautiful round flowers have lost their color and look faded. I had this same issue last year and purchased what I was told was needed to bring the color back. I mixed the stuff with water and it was a messy task. The colors changed very little.
I was told last year to put pennys around in the soil and it may change the colors. I did not do that last year, but this year I did. Well, shortly after that, I had one flower turn purple, but the other still remain faded. Do you know of this quirky way to color Hydrangias or is it just a coincident that one turned. I love these flowers, but I am so frustrated because I cannot keep color in them. Please let me know what else I can do besides make that God awful solution, which by the way smells badly.
Thank you,
Nancy Freid

Change color of pink and red hydrangea to blue

Sprinkle a few spoons of ordinary Epsom salts a couple of times in a growing season. White color cannot be changed.

Hydrangea Color Change

I used to put used SOS pads in the soil. It worked fine, changing from pink to blue.