How to Change Hydrangea Colours – Pink, Blue & Purple Flowers?

Growing hydrangeas is like having your floral rainbow right in your backyard. With minor tweaks, you can change the flower color of hydrangeas from blue to pink or even purple.

Most assume the soil pH determines flower color. But Michael Dirr (an American Horticulturist and Professor) says blossom colors aren’t defined by pH per se; instead, they are determined by the amount of aluminium the plant can observe from the soil.

To make it simple, hydrangea flowers turn pink in alkaline soil, and blooms in acidic soil are blue.

Why Do Hydrangeas Change Color with Soil pH?

bone meal for hydrangeas

Hydrangeas flowers undergo a remarkable color transformation influenced by the pH level of the soil they grow in. This change occurs due to a fascinating interaction between the plant’s genetic makeup and the presence of specific minerals in the soil.

In acidic soil with lower pH, aluminium becomes more soluble and accessible to the plant.

So, if you’re growing hydrangeas in acidic soil, they’ll blossom into beautiful blue flowers. This happens because aluminium ions in the soil team up with the petals’ natural pigments, creating that eye-catching blue hue.

On the other side, if your hydrangeas are planted in alkaline soil with a higher pH, aluminium becomes less available.

Thus, the plant opts for more phosphorus absorption. This change results in hydrangeas blooming in stunning pink or red shades, as phosphorus interacts uniquely with pigments, bringing forth those vibrant hues.

Basically, the pH level of your soil plays a significant role in determining which minerals are available, like aluminium, which in turn impacts the colors your hydrangeas will display. It’s like nature putting on its dazzling show of color right in your backyard.     

How to Make Hydrangeas Blue?

Let me make this clear: not all hydrangea varieties change color.

Only certain specific hydrangea plants, such as Bigleaf Hydrangea, Lacecap Hydrangea, Mountain Hydrangea, Tea of Heaven Hydrangea, Oakleaf Hydrangea, and French Hydrangea, are known to change flower color based on soil pH.

So, you’ve pink or red-hued hydrangeas, and you’d like to turn them blue.

As already mentioned, to change blooms to blue, the soil must be acidic.

  • Conduct a soil test and add sulfur or aluminium sulfate to the garden soil.
  • Naturally, in alkaline soil, add 4 tbsp of aluminium sulfate to 1 gallon of water and water the hydrangea plant after every 2 weeks.
hydrangea in clay soil

Also Read: 17 Orchid Growing Mistakes New Gardeners Make

How to Change Hydrangea Color to Pink?

As mentioned above, hydrangea flower changes to pink to red color if they are taking aluminium from the soil.

Plant roots are able to absorb aluminium from the garden soil if the pH is alkaline.

In case your garden soil is acidic, adding lime can increase pH and make it alkaline.

  • Test Your Soil pH: Start by testing your soil’s pH level using a soil testing kit available at garden centres or through your local agricultural extension office. You’re aiming for a pH level above 6.0.
  • Add Lime: If your soil is too acidic (pH below 6.0), you can raise the pH by adding agricultural lime. Follow the instructions on the lime package carefully, as the amount needed will depend on your soil’s pH and texture.
  • Incorporate Organic Matter: Mixing in compost or well-rotted manure can also help to raise the pH of your soil over time, providing a gradual and natural approach to soil amendment.
  • Apply Fertilizer: Use a fertilizer with a higher phosphorus content and lower nitrogen content, as phosphorus encourages pink flower coloration. Look for fertilizers labeled for promoting flowering or formulated explicitly for hydrangeas.
  • Watering and Maintenance: Keep your hydrangeas well-watered and monitor the soil pH periodically to ensure it remains within the desired range for promoting pink flower coloration.
are eggshells good for hydrangeas

Check this: 19 Best Indoor Flowering Plants Even Beginners Can Keep Alive

How to Turn Hydrangea Flower to Purple?

Getting purple-coloured hydrangea blooms can be challenging.

Acidic soil makes blossoms blue.

Alkaline soil turns them pink.

To get purple-coloured blossoms, you must get a neutral soil pH ranging from 6-7.

Achieving hydrangeas’ actual purple color can be a bit more challenging than shifting them to blue or pink. While some hydrangea varieties naturally produce purple blooms, the color can vary depending on soil pH and other factors.

  • Choose hydrangea varieties known for their purple blooms, such as ‘Endless Summer – Twist-n-Shout,’ ‘Nikko Blue,’ or ‘Amethyst.’ These varieties are more likely to produce purple flowers under the right conditions.
  • Aim for a slightly acidic to neutral soil pH, ideally around 6.0 to 6.5. This pH range can sometimes encourage hydrangeas to produce purple blooms. However, the exact color achieved can vary depending on the specific genetics of the plant.
  • Ensure your hydrangeas receive the right amount of sunlight for optimal flower development. While hydrangeas generally prefer partial shade, providing enough sunlight can help intensify flower color.
  • Apply a balanced fertilizer that includes micronutrients, as deficiencies in certain minerals can affect flower color. Avoid excessive nitrogen, as it can promote lush foliage growth at the expense of flower development.
  • Keep the soil consistently moist but not soggy. Hydrangeas prefer well-drained soil, and fluctuations in soil moisture can impact flower color and overall plant health.

Also Read: Best Manure for Flowers


To wrap it up, getting blue or pink-coloured hydrangea blooms involves creating the right soil conditions.

By lowering the soil pH to acidic levels, typically below 6.0, you can encourage the presence of aluminium ions, which team up with natural pigments in the petals to bring out that striking blue color.

Also, choosing hydrangea varieties known for their blue blooms and making sure they get enough sunlight and water will help them flourish.

With these steps and a bit of patience, you can turn your hydrangeas into a stunning show of blue, adding a beautiful touch to your garden scenery.