Blue muffin viburnums are naturally compact with a rounded silhouette. Because of how they grow, viburnums don't need pruning every year. Prune them to maintain shape and for the health of the shrub. Be careful, though, as blue muffin viburnums produce flowers from buds formed the previous summer. This means pruning after mid-summer will remove the buds needed to form flowers the next year. Do not remove all of the faded flower bracts. Leave some of the flowers intact so the shrub will produce the wonderful blue berries for which it is named.
Prune your blue muffin viburnums in early summer when the flowers begin to fade. This will help to maintain their shape.
Examine your blue muffin viburnum to ensure that it has a rounded shape with branches all the same length. If the viburnum has the correct shape with growth, it need not be pruned.
Cut back uneven growth to just above a strong bud or node, the greenish bump on the branches where new growth emerges.
Prune to maintain your blue muffin viburnum's health by removing dead, diseased or broken branches. Do this any time of the year and make the cuts 3 to 4 inches into healthy wood.