How to Change the Color of Your Hydrangeas Naturally

I LOVE Hydrangeas. I really do!

These flowers are so beautiful that I’m always planting more of them in different colors. Whenever I find Hydrangeas on sale, I just buy them!

To my surprise (seriously, I was shocked!), I don’t need to buy Hydrangeas in different colors, because it’s possible to change the color of your Hydrangea in a very simple way. It may seem strange or unreal, but the truth is that it is possible!

This color-shifting magic isn’t just a gardener’s myth – it’s a natural phenomenon that you can control with just a few simple steps. In this article, we’ll show you how to change the color of your hydrangeas naturally, and you’ll see just how easy it can be.

First, Understanding Hydrangea Color Changes

Before diving into the how-to, it’s important to understand why hydrangeas change color.

The color of most hydrangeas, particularly the popular bigleaf (Hydrangea macrophylla) varieties, is influenced by the pH level of the soil:

Acidic Soil (pH 5.5 or lower): Produces blue or purple flowers.
Neutral to Alkaline Soil (pH 6.5 or higher): Produces pink or red flowers.
Slightly Acidic to Neutral Soil (pH between 5.5 and 6.5): Can result in a range of shades, including lavender or a mix of pink and blue on the same plant.

This color change is primarily due to the presence of aluminum ions in the soil, which hydrangeas absorb differently depending on the soil’s pH.

Acidic soil makes aluminum more available, leading to blue flowers, while alkaline soil locks it away, resulting in pink flowers.

Changing Hydrangea Color to Blue

If you dream of having beautiful blue hydrangea blooms, you’ll need to lower the pH of your soil to make it more acidic. Here’s how:

1. Test Your Soil pH

Before you start, it’s a good idea to test your soil’s pH. You can purchase an inexpensive soil pH testing kit from a garden center or online. If your soil pH is above 6.0, you’ll need to lower it to around 5.5 or below for blue blooms.

2. Add Soil Amendments

To lower the soil pH and encourage blue hydrangeas, you can add the following amendments:

Aluminum Sulfate: This is the most effective way to make soil more acidic quickly. Mix 1 tablespoon of aluminum sulfate per gallon of water and apply it to the soil around the base of your hydrangeas every 2-4 weeks during the growing season.
Organic Matter: Adding organic materials like coffee grounds, pine needles, or composted oak leaves can help acidify the soil over time.

3. Monitor and Adjust

Continue to monitor your soil pH throughout the growing season. If the pH starts to rise again, apply more aluminum sulfate or organic matter as needed. You should start to see a color change in your blooms by the following growing season.

Changing Hydrangea Color to Pink

If you prefer pink hydrangeas, you’ll need to raise the pH of your soil to make it more alkaline. Here’s how to do it:

1. Test Your Soil pH

As with changing to blue, start by testing your soil’s pH. If your soil is acidic (below 6.0), you’ll need to raise it to around 6.5 or higher to achieve pink blooms.

2. Add Lime

To make your soil more alkaline, add garden lime (calcium carbonate) to the soil around your hydrangeas. Follow the package instructions for the appropriate amount based on your soil’s current pH and the size of your hydrangea plant.

3. Use Fertilizers with Low Phosphorus

Phosphorus can make aluminum in the soil less available, so use a fertilizer with a low phosphorus content to encourage pink blooms. Look for fertilizers with a higher ratio of nitrogen and potassium, and avoid those labeled as promoting flowering (high in phosphorus).

Tips for Success

Be Patient: Changing the color of hydrangeas is not instant. It can take a full growing season for the color to change completely.
Consistency is Key: Regularly check your soil pH and make adjustments as needed. Once you achieve your desired color, maintain the soil conditions to keep it that way.
Know Your Variety: Not all hydrangeas can change color. This method primarily works with bigleaf and mountain hydrangeas (Hydrangea macrophylla and Hydrangea serrata). Other types, like oakleaf or panicle hydrangeas, have fixed flower colors regardless of soil pH.