How to Prune hydrangea 'Pia'?
Use the method for the hydrangea type: remove faded mophead flowers to the first healthy bud pair; paniculata and arborescens may have last year's stems shortened to healthy bud pairs. Climbing hydrangeas need overlong shoots trimmed after flowering. Most types are pruned in late winter or early spring; climbing hydrangeas are pruned after flowering in summer.