Hydrangea Color

Changing Hydrangea color - one of the most interesting things about Hydrangea (also called hortensia) is that some of the species can change their flower color.

We always want more flower colors and different ones than what we have!
 
I think it works something like the curly-straight-hair-thing… many people with straight hair would love to have curly hair and many who have curly hair long for straight hair. Those who have pink Hydrangea would also love to have blue and purple flowers and those with blue flowers would love to have pink flowers too.

Hydrangea macrophylla (bigleaf) is the main species with the characteristic to change bloom color.  The colors range from deep pink, to deep blue and purple and all the shades in between.

Changing Color
Some cultivars of  H. macrophylla change color easier than others.

How to get Pink
The basic color of most cultivars of the bigleaf is pink in neutral soil. If you want pink blooms and have blue at the moment you need to raise the pH of the soil to be less acidic. You can do this by adding hydrated lime and ground lime (not quicklime or builders lime).

How to get Blue
Start with a cultivar that turns blue easily like Blaumeise, Bodensee, Nikko Blue, or Renate Steiniger. There are more to choose from than this short list of plants.

Add aluminum sulfate to the soil. This will also make the soil more acidic.
 
In some cases it’s possible to get blue blooms with a soil pH of 4.5 and above. We have a Hydrangea that produces blue flowers and the soil is only slightly acidic. We haven’t tried to influence the color. I have to add that the blue of the flowers are not that deep and intense and I guess it’s possible that the soil is more acidic deeper down.

If you add aluminum sulfate and the flowers do not become or stay blue then you will have to work on the soil to lower the pH to get it even more acidic.

Photo courtesy of Marjon Kruik
Marjon has also told us more about
this Hydrangea in Brittany, France.

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Hydrangea in Brittany, France  I visited Brittany a few times during my summer vacation. During those trips I saw a lot of flowers, especially Hydrangea. That's a very popular flower ...