By Grannysal
Dorset,
United Kingdom 
I've had this particular hydrangea bush for probably 40 years plus..... Always been pink. This year it's a lovely purple blue, without any help from me, any ideas why ?
5 Jul, 2018
Answers
Not added anything at all seaburngirl. A
Mystery - thanks !
6 Jul, 2018
They can be a bit mysterious. I have a dark red one that was starting to look a bit bluish so I added some lime which is supposed to encourage red. Instead they began to look a bit more bluish. ???
7 Jul, 2018
the pH of your soil has changes a bit that's all. more acidic than normal. Have you added peat or pine needle type mulch around it? have you fed it with an azalea feed?
5 Jul, 2018