How to Change The Color of Your Hydrangeas in 6 Simple Steps

So you've decided you want to change your hydrangea's color to vibrant pink, beautiful blue, or a vivid violet? Some varieties of hydrangea will adjust their flower color based on the nutrient values of the soil. In this article, gardening expert and hydrangea enthusiast Jill Drago walks through how to change the color of your hydrangeas in 6 simple steps!

Color Changing Hydrangea

The flowers of the hydrangea plant are straight out of a dream. Their prolific blooms are sought after by both amateur and expert gardeners alike. Sometimes though, those hydrangea dreams are just maybe a tad less vibrant than we were hoping for though. Are you wishing your blue hydrangeas were pink, or your pinks were blue? Maybe you want to add in some purple to your garden? If so, you’ve come to the right place!

Hydrangeas are stunning plants that can reward gardeners at just about every skill level. There are species of hydrangeas that are a bit more flexible in their color changing capabilities than others. This is a very unique characteristic in a plant.

If you have Hydrangea macrophylla or Hydrangea serrata you have a unique opportunity to play with the colors of your flowers! Follow along with these simple steps to learn if you have the right kind of hydrangea, and how to change the color of your flowers.

Check Your Species

Blue Macrophylla Species
Only certain hydrangea types react to the pH levels of a soil with color sensitivity.

When it comes to hydrangeas that have pH sensitive flowers you want to be looking for Hydrangea macrophylla, or bigleaf hydrangea. This is the most common. To a certain extent H. serrata or mountain hydrangea can also have pH sensitivity.

If you aren’t sure what type of hydrangea you have growing in your garden you can identify these plants in a few ways. One is to check the flower buds: if the buds open into blue, pink or purple flowers you have a macrophylla. Flowers that open green point to Hydrangea arborescens, which flowers are not sensitive to soil pH and cannot be changed.

If your flowers have not bloomed yet you can take a peek at the leaves. Bigleaf and mountain hydrangeas both have toothed leaves with short petioles.

The petioles are small stems that connect the leaves to the main stem. If you have a bigleaf hydrangea there will only be groups of two leaves at any given point on the stem. If you see groups of three leaves it is likely a panicle hydrangea.

The only types of these species that will change color are flowers that are already in shades of pink or blue. Flowers that are white will always be white as they are not sensitive to the pH balance of the soil.

If you are serious about having pink or blue hydrangeas be sure to start with a variety that is blue or pink to begin with. You can then use the below techniques for bluing or pinking to attempt to intensify the color if needed.

Test your Soil

Putting Garden Soil in Bag
Soil testing is a great way to ensure your planting area has the right nutrient balance.

Before you add anything to your garden, even a basic fertilizer, it is always a good idea to perform a soil test. You can find soil tests at your garden center that you can do right at home.

If you have a local county extension office, or a local university with experts in plants or soil science they may also have a lab that will perform these tests for you. Oftentimes, these offices will provide you with more in depth information as well as recommendations for your soil.

Soils that are more acidic, or below 5.5 pH, will favor blue flowers by allowing the hydrangea to absorb more aluminum. Whereas alkaline soils or soils that are above 6.5 pH, also known as  “sweet” soils, will produce pink flowers on your hydrangea.

Sweeter soils typically lack the aluminum needed to produce blue blooms. Remember, before amending your soil with anything a soil test is recommended.

Changing To Blue Flowers

Shrub With Flowers in Full Bloom
Hydrangeas with blue blooms are some of the most sought after.

Before we start, it’s worth noting that it’s easier to change to pink from blue, than it is to change to blue from pink. But that doesn’t mean it can’t happen! There are some specific steps, and careful monitoring that you’ll need to take, when attempting a color shift to blue flowers.

Keep in mind that it takes weeks, if not months to change colors, especially to blue. If it all sounds like too much work, consider heading out to your local nursery and finding a hydrangea variety that has blue blooms from the start. You can then just maintain the pH balance of the soil. Before you go to that extreme, try the steps below and wait to see your results!

Add Aluminum Sulfate

Color Changed Shrub
Aluminum sulfate is one of the primary tools used in changing hydrangea blooms to blue.

The best tool to improve blue blooms is aluminum sulfate. It’s readily available and cost effective. Usually, “less is more” when using this on your hydrangeas. All that’s needed per gallon of water is one tablespoon for the safest application rate.

Make sure the plant isn’t too dry before applying this solution. If dry, water it at the base, not from the top. Applying aluminum sulfate to a dry plant can cause burning. Similar to garden lime, this should only be done two times per year. Once in April, and again towards the middle or the end of May.

There are also commercial products available to help change the color of your flowers. Both Endless Summer and Espoma have an easy to use product that is available at most garden centers and is very user friendly.

Add Organic Matter

Peat Moss in Garden
Adding compost or peat moss can help lower the pH of your soil.

Another way to slowly lower the pH of your soil is by adding organic matter into the soil. Good options for organic matter are compost or peat moss.

While this method is a bit slower, it is much better for your soil overall. There is much less risk if you are using organic matter as well; you can incorporate it into the soil whenever you like and you will not need to worry about burning your plant. It will also benefit the overall health of the plant, not just the color of the flowers.

Use High Potassium Fertilizer

Adding Fertilizer to Soil
Adding a fertilizer that contains higher levels of potassium can help with the color change.

When you are fertilizing your plants, you can use a water soluble fertilizer such as Miracle-Gro to help your blue flowers along. Traditional fertilizer is broken into N-P-K: nitrogen, phosphorus, potassium.

In the case of blue flowers you will want that third number to be a bit higher, such as a 5-7-10 fertilizer. The higher amount of potassium will help the plant absorb aluminum which in turn will help your flowers turn blue.

Changing to Pink Flowers

Pink Flowering Shrub
Many gardeners decide to seek out the hydrangea’s vibrant pink blooms.

Turning blue flowers pink, is a little bit easier than changing pink flowers blue. You’ll look to increase the the pH levels of the soil using a couple of tried and tested methods.

Before you head down the road to pink, just keep in mind that as mentioned, it’s a longer road coming back. It can take time, and some patience. Many gardeners just opt for completely replacing the plant if they aren’t getting the desired results.

Ready to rock some pink blooms? Follow the next two easy steps!

Add Garden Lime

Garden Lime in Soil
Garden lime is a great tool to increase the pH levels of most soils.

Garden lime is the best tool to use if you are looking to enhance the reds or pinks of your hydrangeas. Apply the powder form of lime to the plant’s base in April, and again in October. The pH of the soil will be raised by garden lime. This prevents your hydrangea from utilizing the aluminum, which enhances both the reds and the pink blooms.

You can opt to add dolomitic lime to the base of the plant and water it in. Or you can add hydrated lime at a rate of one tablespoon of lime to one gallon of water and apply monthly beginning in the spring.

Similar to products for blue flowers, there are also products available for pink hydrangea flowers. Again, Endless Summer has a product and Espoma has a Garden Lime product that is recommended for assisting the pinking of your flowers. 

Use High Nitrogen Fertilizer

High Nitrogen Fertilizer
Using a fertilizer that has a higher nitrogen and phosphorus count can help change soil chemistry.

Again, similarly to fertilizing for blue flowers you can choose a hydrangea fertilizer that has a higher nitrogen and phosphorous amount. Remember, fertilizers are broken down into N-P-K ratios (nitrogen, phosphorus, potassium).

A basic 10-10-10 fertilizer will do the job here. The high nitrogen will help to balance out the high pH of the soil, where the phosphorus will push flower growth.

Do take note of how much of this fertilizer you are using, especially if you notice that your amount of flowers seems to be decreasing from season to season.

Changing to Purple Flowers

Purple Flowering Shrub
Usually, a color swap to purple blooms is the easiest of the three.

Changing to purple is likely the easiest of the three color changes. That’s because the pH required falls in between the pinks and the blues. So, if you want to turn your hydrangeas purple, you can work your way forward or backwards from the steps listed above.

If you are working from pink to purple, you’ll want to ensure your aluminum levels are correct, and add aluminum sulfate if they are not. You can also lower the soil pH using an organic compost.

If working from blue to purple, follow the same steps you’d take to get to pink. Amend the soil with garden lime and phosphorus. Less is more, so start slowly, and see how your hydrangea’s blooms react.

Consider a Container

Hydrangea in Terra Cotta Container
Planting in a container will allow an easier adjustment of soil nutrient levels.

If you live in an area where it is too difficult to amend your soil you always have the option to plant your hydrangeas in a container. Choose a large container with a drainage hole on the bottom so that hydrangea has room to grow and drain.

Give the container a good cleaning to remove any debris or bug eggs. Use potting soil with fertilizer mixed in as opposed to your garden soil which may be too heavy, and may not have the pH you are hoping for. Add the shrub into your container, backfill with potting soil and water until water drains from the pot.

Once you have gotten your hydrangea settled into the container you can begin to amend for your desired color as we talked about above.

Select a location for your container that has the right amount of sun, typically bigleaf and mountain hydrangeas prefer morning sun and afternoon shade. This will not only keep the plant healthy overall, but it will protect the flowers from becoming bleached by the sun.

Final Thoughts

No matter which way you choose to manipulate the color of your hydrangea flowers it is an easy enough process to do, especially with all of the products available to gardeners at hardware stores or garden centers.

Something to keep in mind is these fertilizers or additives will not necessarily make your flowers brighter, or richer in your desired color. These blues and pinks will likely be pastel in shade. Adding more of the additives will not help your colors brighten, it will likely only damage your soil.

Keep in mind that it’s easier to turn pink hydrangeas blue rather than blue to pink. This is because it is difficult to remove naturally occurring aluminum from the soil. Whichever method you choose, be sure to follow all package instructions, and have some fun with changing the colors of your beautiful shrubs!

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