How much ground coffee can i add to my hydrangea in order to keep it blue
By Sevelyn
United Kingdom 
Many thanks for the response. Greatly appreciated. I will buy ericaceous compost very soon.
10 Jul, 2011
Answers
You can also buy a little tub of 'Hydrangea colourant' which contains what they need to be blue.
10 Jul, 2011
If its in a pot, go and buy a bag of ericaceous compost and repot into that - coffee grounds have a mildly acidifying effect, but as its in a pot, its far easier to put it in acidic compost.
10 Jul, 2011