When is the proper time to prune a hydrangea? I have an old hydrangea that has a lot of old large canes. Do I leave the flower heads on until I prune?

The proper timing to prune hydrangeas depends on what type of hydrangea you are growing. Bigleaf hydrangeas produce blooms on previous years growth. Prune back stems that have flowered to about 2 feet high, right after they finish blooming. As Pee Gee hydrangeas flower on new growth, they should be pruned in early spring to about 6 - 12" height. Oak leaf hydrangeas require very little pruning but can be pruned in early spring.