When and how do you prune a hydrangea tree? This photo is taken May 1st, 2018.
Pruning Hydrangea Trees
Certified GKH Gardening Expert
That is a very old specimen, it looks like! Pruning will depend, largely, on when it flowers. You will want to prune the growth right after the flowers fade. This article will give you more information: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/prune-hydrangea-bushes-hydrangea-pruning-instructions.htm