I cut my hydrangea right back once it has finished flowering. It was very late this year and nowhere near as nice as it has been in previous years. It is in a pot and is about 4 years old.(when I say right back,I mean almost to the ground)
Mine haven't been too good this either giveup,everything seems late due to last years really wet summer and a very cold winter .
I never cut mine straight after flowering.I always wait until around the following March or at least until the frosts are over to cut the mopheads and prune out any woody growth .
That is what I usually do,but wondered if cutting it right back would encourage it to make stronger growth. I don't want to kill it,its so pretty usually.