Maegan-Leigh JacobsHydrangeas are a charming addition to any garden, and what makes them even more fascinating is their ability to change colour based on the soil they’re planted in.
This unique trait allows you to influence the hue of your blooms, creating a customised palette that suits your garden’s aesthetic, or if you’re a fan of only pink or blue hydrangeas, to only plant one colour.
The science behind hydrangea colours
The colour of hydrangea flowers, particularly those of lace cap and mophead varieties (Hydrangea macrophylla), is largely determined by the pH level of the soil.
Simply put, acidic soil (with a pH lower than 6.0) results in blue or lavender-blue flowers, while alkaline soil (with a pH above 7.0) leads to pink or red blooms. If your soil falls in the neutral range (between 6.0 and 7.0), you might see purple or bluish-pink flowers.
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READ MORE: Essential caring tips for hydrangeas
How to change the colour of your hydrangeas
Follow this step-by-step guide:
1. Test your soil
Start by determining the pH of your soil. You can purchase a soil test kit or send a sample to your local agricultural extension service for analysis.
2. Adjust the pH
To encourage blue blooms: If your soil is too alkaline, you can lower the pH by adding garden sulfur or aluminum sulfate. Follow the instructions on the packaging for the best results.
To encourage pink blooms: If your soil is too acidic, raise the pH by incorporating ground lime into the soil.
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3. Be patient
Changing the colour of your hydrangeas is not an overnight process. It may take several applications and a few months to see a difference in the bloom colour. Remember that not all hydrangeas will change colour, and white varieties typically remain white regardless of soil pH.
4. Re-test and reapply
After making adjustments, re-test your soil to ensure it’s within the desired pH range. You may need to reapply the garden sulfur or lime periodically to maintain the correct pH level.
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A note on store-bought hydrangeas
If you’ve purchased a hydrangea in a pot, don’t be surprised if the colour changes once it’s planted in your garden.
The soil pH in your garden will ultimately determine the bloom colour, so it’s worth testing and adjusting if you want to maintain or change the hue.
ALSO SEE: HOW TO DRY AND PRESERVE HYDRANGEA FLOWERS
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