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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.
Your soil is probably alkaline.....try a PH test .....so blue hydrangeas won't like it. The rule is acid soil for blue hydrangea and alkaline soil for red or pink hydrangeas. Also the variety itself.......do you know it's name? It may be a red or pink variety.
I suggest you test your soil.....if its acid then buy a good named blue variety. ??ou will have no need of any blueing agent then. Always best to grow plants suitable for your soil and conditions
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.
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.
Note the VARIETY of hydrangea is important too. Blue varieties for acid soil and red for alkaline. Top dressing an alkaline soil with ericaceous compost is wasteful and ineffective. It will not work. Whatever your hydrangea colour is work with it.....it will be much happier if you concentrate on keeping it watered well. The well tried maxim is....grow what your soil supports