While there are over 150 varieties of viburnum, one of the most popular is known as the "snowball bush." Attaining tree size at 12' by 12', clusters of tiny white flowers resembling snowballs cover the plant in spring. A hardy shrub that does well in zones 2 to 9, it is easy to plant and care for, and requires very little maintenance. However, at times, a pruning can keep the perennial from growing too quickly, and help it maintain optimal health and shape.
Decide why you wish to prune, as not all plants need pruned annually. Are there dead branches? Is the plant growing in an unsightly shape? Do the internal branches need thinned? Or is it growing out of control in an area with inadequate space? It is helpful to determine the necessity of pruning before arbitrarily cutting any flowering bush or shrub.
Prune only after the bush has finished blooming. Blooms appear on the previous year's growth. It is essential not to cut this prior to the arrival of spring blossoms.
Remove any damaged branches, or those that look diseased or dead, first. Cut the branch back to healthy wood and carefully pull the unwanted branch out of the shrub.
Prune any branches clustered tightly together, especially if several cross each other. Also remove any that are beginning to intertwine. This allows sunlight and proper ventilation to reach the remaining branches.
Cut any branches back that show accelerated growth by sticking out above other limbs. Level these with the remaining branches to allow the bush to keep a natural-looking shape.
Trim any root shoots or "suckers" at the base of the shrub, or on the ground directly below; these can develop into additional plants that threaten the health of the pruned bush. However, the removed shoots can be rooted in pots to start additional bushes for your yard, or to give away.