I heard about burying rusty nails around your hydrangea to change its colour, I don`t know if this is true though.
My hubby used to add metal filings around the rooting of mine and each year they would turn a different colour.
Well I wouldn't let him touch my lace cap hydrangea or my white one but I did have 3 pinks and the next year when flowering came a deep purple but I also saw metal on the gravel and when I asked him what it was he then told me what he was doing...they came out in lilac and in the end you'd get the colours mixed pink / lilac / purple...the metal filings do change the colour of them.
