Moving a large 7 ft hydrangea

I think you can take Irishman's cuttings at most times, @shiney is better able to explain then me.

 

Yes, an Irishman's cutting is the term for 'cuttings' that have roots on them. Hydrangeas are very good for that. What you get with them are root runs and that is how the plant expands its perimeter. So look around the plant for newer shoots (they can be quite tall) that are near the perimeter. Dig them out and cut the link where they are running to the main plant. You now have a rooted cutting. It is best to pot it up for a few weeks where you can pamper it a bit.

Transplanting Hydrangeas can be done most of the year but not during hot dry spells so I would be inclined to wait until Autumn as Nigel says.

Good luck