Trimming hydrangeas to the ground can weaken them over time.
Dec 12, Your new snowball bush (Viburnum opulus) is hardy in zones so it will survive your winters without problem. I wouldn't wrap the branches, but I'd mulch over the root area just to keep them protected this first year. If there's any winter damage evident next spring, prune it off to encourage healthy new growth.
Dec 17, H. macrophylla, H. paniculata and V. macrocephalum snowball bushes respond to complete renewal -- cutting the shrub to the ground -- but may take more than one season to resume heavy blooming. Sep 21, Cut a stem from the snowball bush that is the current year’s growth.
Current stems on the shrub are suitable for rooting when you bend a stem and it snaps into two pieces. Select a 6-inch stem with leaves and cut the stem just under a leaf node.