Posted: 30/08/2015 at 15:12
Jack, those hydrangeas that dont do well, are they in pots? If so they need a decent soil in those pots not the multi purpose compost usually bought. These composts simply do not have enough oomph in them to conserve the water you give them...probably goes straight through leaving roots fairly dry.
what I am suggesting is using a different form of compost in those pots....a john innes type. Ask at the garden centre for it.
no, dont feed beyond the summer months at all. Its probably just the compost you need to change
hydrangeas will always do best in the ground