Removal of dead branches is the only pruning recommended during the first three to five years after planting. After this, every year or two in early spring or late winter, before growth begins, remove broken branches and thin out weak and small shoots from the center of the bush. Prune older branches when bush gets too dense, never more than 25% of a bush at a time.

Thanks for the detailed info on pruning. I think I need to create another bed!