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How to Change Hydrangea Color

February 13, 2024

The Magical Palette of Hydrangeas – Transforming Your Garden with Color

Introduction to Hydrangeas

Blue to Pink? Or Pink to Blue?

Hydrangeas, with their large, vibrant blooms, are like the chameleons of the plant world, bringing a burst of color and life to any garden. These perennials are loved for their lush foliage and clusters of flowers, ranging from deep blues to vivid pinks, and even pristine whites and greens. They are not only a gardener’s delight but also a staple in many landscapes for their versatility and ease of care.

The Science of Hydrangea Color Change – Understanding pH Levels

The most fascinating aspect of some hydrangea varieties is their ability to change color. This color change is not a garden myth but a scientific reality, deeply rooted in the chemistry of the soil. The secret lies in the soil’s pH level, a measure of how acidic or alkaline the soil is. In simpler terms, soil pH affects the availability of aluminum ions which are absorbed by the hydrangea, influencing the color of the blooms.

  • Acidic Soil (pH below 6) Promotes blue hydrangea blooms. The higher availability of aluminum ions in acidic soil allows these ions to be more easily absorbed by the plant, leading to blue flowers.
  • Alkaline Soil (pH above 7) Favors pink hydrangea blooms. In alkaline conditions, aluminum ions become less available, preventing the plant from absorbing them, which results in pink flowers.
Soil pH RangeBloom ColorUnderlying CauseNotes
Below 5.5BlueAluminum readily available, binds to flower pigments creating blue tones.More vibrant blue with lower pH, may require aluminum amendments in naturally alkaline soil.
5.5 to 6.0Purple or mixed blue and pinkSome aluminum available, creates a mix of blue and pink pigments.Color variation possible within individual plants.
6.0 to 6.5Pink or whiteLimited aluminum availability, pink pigments dominate.Natural color of some hydrangea varieties, may require lime additions in naturally acidic soil.
Above 6.5Pink or white (may be washed out)Aluminum unavailable, pink pigments dominate, but color intensity can be weaker.Not suitable for blue hydrangeas, may require significant lime additions for pink color.
How to change hydrangea color with pH

Cultivars That Can Change Color

Not all hydrangeas can change color. The ability to shift hues is primarily found in the Hydrangea macrophylla (bigleaf hydrangeas) group. Popular cultivars in this category include:

  • ‘Endless Summer’ Known for its ability to bloom on both old and new wood, making it a reliable choice for colder climates.
  • ‘Nikko Blue’ A classic variety with large, round flower heads that can turn a stunning deep blue in acidic soils.
  • ‘Pistachio’ Features a mix of vibrant red, green, and blue flowers, depending on the soil pH.

Step-by-Step Guide to Changing Hydrangea Colors

  1. Test Your Soil pH Before attempting to change the color, test your soil with a pH testing kit available at garden centers. You can also utilize a soil meter for pH.
  2. Altering Soil pH
    • For Blue Hydrangeas To acidify the soil, you can add garden sulfur or aluminum sulfate. Be careful with aluminum sulfate as it can harm the roots if overused.
    • For Pink Hydrangeas To make the soil more alkaline, add lime. This reduces aluminum ion availability, shifting the bloom color towards pink.
  3. Application Apply these additives around the base of the plant and water them in well.
  4. Patience is Key The change won’t happen overnight. It can take several months or a growing season for the color change to fully develop.
  5. Regular Maintenance Continue to test soil pH and adjust treatments as necessary.
Master Gardener Tip: Apply the soil amendment right before a rainstorm. The rain will naturally dissolve the amendment and bring it into the soil slowly over time for the roots to absorb.

Watch Our Video Tutorial an Changing Hydrangeas


Transforming the color of your hydrangeas can be a fulfilling gardening project, allowing you to customize the palette of your landscape. It’s a perfect blend of art and science, where a little bit of chemistry leads to a spectacular display of nature’s versatility. Remember, each hydrangea has its unique genetics, so the intensity and exact shade may vary. Embrace the process and enjoy the stunning spectrum of colors these remarkable plants can provide. See our FAQ below for more info. Happy gardening!

FAQ: Changing Hydrangea Color – Top 10 Common Questions

1. Can I change the color of all hydrangeas? Not all hydrangea types can change color. The ability to change color is typically seen in Hydrangea macrophylla (bigleaf hydrangeas). White hydrangeas, for instance, cannot change color.

2. What determines the color of a hydrangea? The color of hydrangeas, particularly bigleaf varieties, is greatly influenced by the pH level of the soil. Acidic soil (pH below 6) tends to produce blue flowers, while alkaline soil (pH above 7) leads to pink or red flowers.

3. How can I turn my hydrangeas blue? To turn hydrangeas blue, you need to make the soil more acidic. You can do this by applying a solution of aluminum sulfate or by adding organic matter like coffee grounds, citrus peels, or peat moss to the soil.

4. What should I do to get pink hydrangeas? To achieve pink hydrangeas, you need to increase the soil’s alkalinity. This can be done by adding lime to the soil. It’s important to test the soil pH first to determine the amount of lime needed.

5. How long does it take for a hydrangea to change color? The color change process is not immediate and can take several weeks or even months. It depends on the initial condition of the soil and the measures taken to alter the pH.

6. Will changing the color of hydrangeas harm the plant? Altering the soil pH to change hydrangea color is generally safe if done gradually and carefully. Sudden changes in soil conditions, however, can stress the plant.

7. Can I change the color of hydrangeas in pots? Yes, it’s often easier to change the color of potted hydrangeas since you have more control over the soil composition. Adjust the soil pH as needed for the desired color.

8. How often should I apply treatments to change hydrangea color? It depends on the current soil pH and the desired color. After initial treatment, test the soil pH regularly and reapply treatments as needed, typically once or twice a season.

9. Can I make my hydrangeas a specific shade of blue or pink? While you can influence the general color (blue or pink), achieving a specific shade can be challenging as it depends on various factors including genetics, soil type, and environmental conditions.

10. Is it possible for hydrangeas to be both pink and blue? Yes, hydrangeas can display both colors, especially during the transition phase of altering the soil pH. This can also occur if the soil has uneven pH levels.

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