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Hydrangea colour

I wanted to keep some hydrangeas blue, but they revert to pink.  I have clay soil and have been using colourant on them but so far it does not seem to make a difference.

Any suggestions, please.


  • It is alkaline soil, but I wondered whether adding ericaceous compost to the soil would help. What do you think?

    I imagined that the colourant would maintain/reverert back to the original colour ie blue.  Any thoughts?

  • The natural colour of Hydrangeas is usually pink.  The blue colour is induced by what is in the soil.  You can buy potions to water in and make/keep the flowers blue.  Or you can create your own - just rusty water.  I do it the easy way, anything rusty like old nails, bits of broken rusty metal etc, I just throw them into the middle of the bush at soil level, and let the rain do the rest.  If you ever come across a Hydrangea that naturally has blue flowers, it will be growing near a metal post that will be rusty below ground level.

  • You wont see any difference this year. It will be shown on next's years blooom. As long as the soil is acidic they will be blue. 

  • DovefromaboveDovefromabove Posts: 86,102

    Of course, if you water with tap water and you're in a hard water area that will make the soil alkaline and the colour will start reverting to pink.   If you use rainwater it will not have calcium dissolved in it so will help maintain acid growing conditions.

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.

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