April, just as growth begins, and only to remove dead flowerheads and any dead wood.

The dead heads of the hydrangea are protecting the new bud growth from frost. Prune it now and you won't have any flowers next year.

I thought you pruned Lacecaps in the late summer when they'd finished flowering and Mopheads in the spring :-/

I never prune my lacecap until the fear of frost has gone, sometimes not til May !!

No, Louise, rules are the same for all.

Hmm, i didn't know that !

Would you recommend different pruning if it was necssary to limit the size?

I would say no difference, but that is my thought. They still need the protection during the winter of old growth.

And you lose flowers doing it at a different time, Bernard.

I wondered because no one has mentioned anything but removing dead flowers and dead wood and this wouldn't limit the size would it?

No, it wouldn't - always best to buy the right variety so you don't have an 8 x 8 feet monster in a space 2 x 2, Bernard! One of my clients has this problem - planted by the front door, gets massive, so we compromise and hack back the lower half, sacrificing the flowers there, so people can get in the door. Looks awful though, all you see there all summer is lots of bare twigs, but client won't have it removed. Thus proving the saying you can take a horse to water but you can't make it drink...

Thanks everyone.