How Long Does it Take For Hydrangea Blooms to Change Colors?

Hydrangea flowers are the perfect summer choice to fill your garden with bold textures and dreamy colors. Sometimes, the blues and pinks we dream of do not come to fruition in our gardens. This is simply because of the pH of our garden soils. This can be frustrating, but it is fixable.

Lucky for us gardeners, changing the color of your hydrangea flowers is pretty simple. The question is how to do so properly, and how long will it take for us to see our desired dreamy results?  

If you are ready to change the color of your hydrangea blossoms, continue reading. We will discuss how long this process will take and give some simple instructions on how to change the color of your flowers. 

The Long Answer

Hydrangea serrata (mountain hydrangeas) and Hydrangea macrophylla (bigleaf hydrangeas) are the two types of hydrangeas that are particularly sensitive to the pH level of soil and can change bloom color. Panicle, oakleaf, and smooth hydrangea flowers cannot change color.

Getting that ideal shade of blue or pink can take several weeks, months, or even years. It depends on the soil’s existing composition and how often it is amended. Most soil pH amendment products should be applied every 2-3 months until the necessary pH level is established. Practice patience here!

For example, if the existing soil is alkaline but you are looking for a blue hue (which requires more acidity), it will take longer for the soil to reach the right pH level to achieve the desired color. This can take up to a few years in some cases.

However, if the soil is already slightly acidic, it wouldn’t need to be amended as much or as often. This means it would be a faster process, even as little as a few weeks.

With that in mind, it is quicker and easier to change your blue hydrangeas to pink rather than pink to blue. A healthy plant will also change faster than an unhealthy one. Another thing to consider is the larger your shrub, the longer it will take for the full-color change to take effect.

How Do I Get Started?

Changing the color of your hydrangea blooms only requires amending the soil’s pH level. However, you need to know a couple of things before you begin this process: the type of hydrangea you are growing and the pH of your soil. Once you have this information, you can get started!

Know Your Hydrangea Species

As mentioned above, not every hydrangea can change the color of its blossoms. This neat trick belongs solely to bigleaf hydrangeas (Hydrangea macrophylla) and mountain hydrangeas (Hydrangea serrata). 

This is easy to determine if you have just purchased your hydrangeas and you still have the plant tag on hand. If not, you will need to do a bit of homework. Take note of when your hydrangea blossoms, what shape the flowers are, and if the flowers appear on older woody growth or newer green growth. 

If you know you are growing a bigleaf hydrangea, there is one more hitch. White flowering bigleaf hydrangeas are not sensitive to the pH of your soil. They will remain white no matter what you do to your soil. If you dream of pink, purple, or blue flowers, you will want to ensure you have the correct species and variety of hydrangea. 

Test Your Soil

Equally as important as your hydrangea species is the pH of your soil. You can either run a full soil test and learn all about the nutrients in your soil as well as your pH, or you can purchase a pH kit at your local garden center. 

Neutral soil has a pH of 6.5-7.5. This means that your hydrangea will likely bloom in a shade of pinkish purple, which can be perfectly lovely.

If your soil is 5.5 or below, your soil will favor blue blossoms. If it is 6.5 or above, you will notice your hydrangeas have more pink or red flowers. Once you have this information about your soil, you can begin amending your soil to achieve your hydrangea flower goals. 

Changing Hydrangeas From Pink to Blue

Achieving the perfect blue flowers takes a bit of time and patience. Some theories claim that regular household items such as vinegar, coffee grounds, or pennies can turn your hydrangeas blue. These methods do not work.

The proper way to do this is to amend the soil with the right acidity. Once your hydrangeas are blue, a few simple steps exist to maintain this unique and vibrant color.

You can begin by fertilizing your hydrangeas with a fertilizer for acid-loving plants such as holly-tone. This fertilizer acts as a basic fertilizer but can also help you lower your soil’s pH. 

Next, you will want to grab aluminum sulfate or a soil acidifier from your local garden center. If you can find a soil acidifier, I would recommend that. It is easy to apply, less harsh, and safer for you and your plants. 

Add your soil acidifier to your hydrangeas in the spring, and repeat every 60 days throughout the growing season until you have reached your goal. If your plants are new, you will want to use 1 ¼ cups of soil acidified. You will use 2 ½ cups per plant if you have established hydrangeas. Sprinkle this evenly around the plant’s dripline, beginning at the center and working your way out to just beyond the farthest branch.  

Changing Hydrangeas from Blue to Pink

Turning your hydrangea blossoms pink or red is a much simpler process that typically has quicker results. You can also use this process to amplify the color of your pink hydrangea blossoms. 

The only thing you need for this process is some garden lime. Garden lime is easy to find at your garden center or hardware stores. Do not apply lawn lime because it will not break down as nicely as the finer granules of garden lime. 

Beginning in April, apply 2-4 tablespoons of garden lime around the drip line of your hydrangeas. The dripline begins at the center of the plant and ends at the farthest-reaching branches. Water your hydrangeas well after applying.

Apply the garden lime again in the fall. Repeat the process in the next growing season and as needed to maintain your desired results. Adding too much too soon can be risky for your hydrangea, so follow the directions on the container to avoid root burn or other problems.

How to Speed Things Up

There is one way you can ensure quicker results: Container planting. 

Hydrangeas make beautiful container plants as long as you have a container big enough for these flowering shrubs. You can change your hydrangea colors quicker in a container because the soil is contained. You can premix additives into the potting soil before you even plant your hydrangeas if you know you will want to change the flower color!