Hydrangeas are one of the most beloved and popular flowering shrubs for landscaping, thanks to their beautiful blooms and their ability to thrive in a range of different environments. One of the unique features of hydrangeas is that their bloom color can be changed based on the acidity level of the soil. In this article, we’ll walk you through few steps you can take to manipulate the pH of the soil and change your hydrangea color.
(Featured Image: Blue Hydrangea by Liz West)
Understanding Hydrangea Bloom Color
Before we get into the specifics of changing the color of your hydrangeas, it’s important to understand why hydrangeas bloom in different colors. The bloom color of hydrangeas is determined by the pH level of the soil. More specifically, the pH level determines the availability of aluminum ions in the soil. Aluminum ions are responsible for the blue color in hydrangea blooms, while a lack of aluminum ions leads to pink or red blooms.
The ideal pH level for blue hydrangeas is between 5.2 and 5.5, while the ideal pH level for pink hydrangeas is between 6.0 and 6.2. Neutral soil with a pH level of 7.0 or higher will produce white or cream-colored blooms.
Changing Hydrangea Bloom Color
Now that we know how soil pH affects hydrangea bloom color, let’s explore how to change the pH level of the soil to achieve the desired color.
1. Test Your Soil pH
The first step to changing the color of your hydrangeas is to test the pH level of your soil. You can do this with a pH soil meter, a soil testing kit or by sending a soil sample to a testing lab. Once you know the current pH level of your soil, you can determine how much you need to adjust it to achieve your desired bloom color.
2. Adjust The Soil pH
If you want to change your blue hydrangeas to pink, or vice versa, you will need to adjust the pH level of your soil. Here are a few methods for adjusting soil pH:
To lower the pH level of your soil (for blue blooms), you can add aluminum sulfate or another acidifier to the soil. Aluminum sulfate is a water-soluble salt that acidifies the soil and makes aluminum more available to the plant. We exclusively use this granular soil acidifier by Espoma for our hydrangeas and have had great success with it. (psst – this can also be used for blueberries!)
To raise the pH level of your soil (for pink blooms), you can add garden lime to the soil. Garden lime is a type of pulverized limestone that neutralizes acidic soil and raises the pH level. Again, it’s important to follow the instructions on the package carefully, as over-application can lead to alkaline soil.
Another option for changing the pH level of your soil is to amend it with compost or organic matter. Organic matter can help to buffer the soil pH and create a more favorable environment for the plant. This method can take longer to show results than adding lime or aluminum sulfate.
3. Repeat The Process
Once you’ve adjusted the pH level of your soil, it’s important to monitor it regularly to ensure that it remains at the appropriate level. Depending on the method you used to change the pH level, you may need to repeat the process annually or every few years to maintain the desired bloom color.
Tips For Changing Hydrangea Bloom Color
Here are a few additional tips to keep in mind when changing the color of your hydrangeas:
It’s best to change the bloom color of hydrangeas during the fall or winter, when the plant is dormant. This gives the soil time to adjust before the plant begins to grow in the spring.
Choose the Right Hydrangea Variety. Not all hydrangea varieties can change color. If you want to experiment with changing the color of your hydrangeas, choose a variety that is known for changing color, such as Endless Summer or Nikko Blue.
Don’t forget to water properly Hydrangeas need consistent moisture to thrive, but overwatering can cause the soil to become too alkaline, which will result in pink flowers. Be sure to water your hydrangeas deeply but infrequently to keep the soil moist without causing waterlogged conditions.
Mulch your hydrangeas with organic materials, such as pine needles, coffee grounds, or compost, to help lower the pH level of the soil and encourage blue flower color.
Fertilize Wisely! While fertilizing can help hydrangeas grow and bloom, it’s important to choose the right fertilizer for the job. A fertilizer high in phosphorus will encourage pink flowers, while a fertilizer high in aluminum will encourage blue flowers.
Try Out A Color Change For Your Hydrangeas
In conclusion, changing the color of your hydrangeas can be a fun and rewarding project for any gardener. By understanding the basics of hydrangea color and following these tips, you can easily transform the color of your hydrangeas to suit your style and preferences. So why not give it a try? With a little patience and effort, you can enjoy a stunning display of hydrangea blooms in the color of your choice.
Anna is one of the owners here at Bright Lane Gardens, and our resident plant and garden expert. Anna started gardening from a young age and has continued to grow her knowledge in the horticulture realm over the years. With a keen interest in sustainable gardening through organic gardening practices and the use of drought tolerant and native plants, Anna is committed to spreading this knowledge through blog posts and Bright Lane Garden's YouTube channel.