Posted: 11/08/2016 at 17:41
Depends on the colour if using seaweed. Not at all on blues in my opinion if you have a really good named blue variety
in the ground I would simply use fish blood and bone in early spring plus a mulch incorporating pelleted chicken manure. A liquid feed is not necessary for hydrangea in the ground. Water is the key thing.
In pots I would use epsom salts and tomato fertiliser if blue In acid john innes. if pink or red Seaweed is fine.