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How do you change the colour of Hydrangeas between blue and pink?

I have heard that this has something to do with acidity in the soil, and you can change it by adding eggshells and things that change the pH. What do you have to do to make Hydrangeas each different colour? And is there any effect on white or red flowers?


The color of your hydrangea flowers is affected by the pH of the soil they are planted in.

This is most noticeable in the blue-flowering forms of both Hydrangea macrophylla and Hydrangea serrata, whose colors can range from bubble gum pink in alkaline soils (pH above 7.0) to rich, sky blue in acid soils (pH below 7.0).

However, even within those two species not all plants may be affected by soil pH. Certain pink/red varieties will always be pink or red, but the intensity of the color may vary somewhat depending on pH. The same may be said for white varieties, which will likely always be white regardless of soil pH.

Generally speaking (there are exceptions to every rule!), it is only the blue/purple-flowering species and cultivars whose color may change dramatically between blue and pink depending on the relative acidity or alkalinity of the soil. The flower color (white) of the popular 'Annabelle' hydrangea, the oakleaf hydrangea and panicle hydrangea are unaffected by soil pH.

Answered by Troy B. Marden...Gardens from USA, Nashville, in June 2010.

Troy B. Marden...Gardens is a Garden Writer, Television Host, Garden Designer

See more about Troy B. Marden...Gardens

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