Q.what type of hydrangea is this and how do I prune it?
Hello: We bought this house in the Boston area 9 years ago and I still dont know how to prune the hydrangeas planted by the last owner. I believe these are either “mophead” or maybe “smooth” hydrangeas. They bloom in the june, july and august (I think) and the flowers are usually white, but then turn greener later in the summer. I think they grow on “old wood” so I think I should be pruning them in later summer but I am not sure, and I dont know how to prune them. Obviously they have gotten too tall for their own good…any thoughts.

Certified GKH Gardening Expert
I do believe that this is a Mophead. This will be pruned in late summer, but no later than early fall. Only prune branches that have already flowered. This article will help: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/prune-hydrangea-bushes-hydrangea-pruning-instructions.htm