Here's how to change the color of your hydrangea

If your hydrangea flowers are pink instead of blue — or vice versa — there's a way to get the color you want. Here's how to change a hydrangea color to the perfect hue.

The plant tags on your 'Endless Summer' hydrangeas promised beautiful sky-blue flowers—so why are the flowers completely pink? To learn how to change the color of hydrangeas, take a close look at the dirt they grow in.

Here is the secret…

It's in the soil! The key to color change for hydrangeas is whether the soil is acidic (low pH) or alkaline (high pH.) For hydrangeas to have a beautiful blue color, the soil should be on the acidic side, with a pH less than six. You can test this with a soil pH meter like this one. You can also check your hydrangea flowers: if they are pink, the soil is alkaline.

Which hydrangea changes color?

Before you think about changing your soil, know that not all hydrangeas change color. Hydrangeas with white or ivory flowers such as Oakleaf, 'Beige' or 'Annabel' are unaffected by soil pH. These hydrangea flowers remain white, although some cultivars such as 'Vanilla Strawberry' may turn from white to pink.

Hydrangeas that can turn from pink to purple to blue are the macrophylla group, also known as bigleaf, lacecap or mophead hydrangeas. (Lacecaps have flat flowers with frilly edges; Mobheads have large, globe-shaped flower heads.) Varieties in this group include 'Endless Summer,' 'Nico Blue,' 'Summer Crush,' and 'L.A. Dreamin'.' Although some of these varieties have "blue" or "red" in their names, all large leaf hydrangeas can change color.

How to get blue hydrangea

To turn your hydrangea flowers blue, lower the soil pH to 6.0 or lower. You can do this by purchasing a soil-acidifying plant fertilizer to feed your hydrangeas every one to two weeks. Or, lower soil pH naturally by spreading pine needles or pine bark mulch around plants. Coffee grounds help make the soil more acidic, as well as compost tea, vinegar or peat moss added to the soil.

A lack of aluminum in the soil can prevent hydrangeas from turning blue. As excess aluminum can be toxic to plants, confirm aluminum levels with a soil test before purchasing additives.

How to get a pink hydrangea

Pink hydrangea flowers require alkaline soil, with a pH of 7.0 or higher. To make the soil more alkaline, you can work in ground or powdered lime or wood ash. You should do this several times during the growing season. Remember that it is more difficult to make the soil more alkaline, so it will take longer than the process for blue flowers.

How to get purple hydrangea

Hydrangea flowers turn red-purple to light purple when the soil pH is between acidic and alkaline. You will often have purple flowers during the process of raising or lowering the pH of the soil. To achieve shades of purple, the pH should be between 6.0 and 6.9.

Be patient with your garden

It takes some time to change the pH of your soil, so be aware that these color changes won't happen overnight. It takes several weeks or even months to amend the soil, and these steps must be taken in subsequent seasons.

If you believe that hydrangea color change will occur quickly, plant a small hydrangea in a container. You can change and control the pH of potting soil very easily, and it's a fun way to experiment with hydrangea color. Here are more ideas to take your garden from good to great!