Fragrant Snowball Viburnum Trimming

Need

• Compared to other shrubs grown in American gardens, viburnums do not require continual, intense trimming or pruning maintenance to look nice and grow with good health. Any dead, broken or diseased branches or twigs may be trimmed off any time of year on snowball viburnum shrubs. Branches that encroach onto a sidewalk or driveway need to be trimmed back for safety. Many aesthetic reasons may cause you to want to trim a viburnum, such as promoting more bushy growth, more flowering or to balance out the silhouette of the plant. If snowball viburnums are never pruned, they still produce a heavy display of white flower clusters and an attractive fall foliage display.

Timing

• Snowball viburnum shrubs develop their flower buds in summer and early fall, and bloom on this young, year-old wood the following spring. The best time to conduct any pruning on viburnums is in early spring, since ample time remains in the growing season for replacement leaves and branches. However, trimming the snowball viburnums in early spring removes the swelling flower buds and reduces the upcoming blossom display. Therefore, you may opt to trim immediately after the flowering display ends in mid- to late spring. Avoid pruning past Labor Day, as any new growth that sprouts won't mature enough in time to survive the first fall frosts and onset of subfreezing temperatures by winter.

What to Trim

• Errant branches, those that jut up awkwardly from the main shrub to spoil symmetry, should be trimmed back. Any branches that grow inward across the center of the shrub or rub against other branches, causing a bark wound, should also be trimmed to remedy the situation. Using a bypass or hand pruners, reduce the length of the branch. Make the cut 1/4 to 1/2 inch above a lower branch junction or pair of leaves or dormant buds.

Tips

• Snowball viburnums develops a rather rounded, but open or tiered branching silhouette. The large leaves are attractive, but are not overly dense. Do not use hedge shears to tip branches to create a uniform, rounded mass. This destroys the natural tiered or billowy silhouette of the viburnum. To reduce shrub size, conduct "feather pruning." This is a time-consuming trimming of every other branch shoot across the plant. In the following year, the other shoots that weren't trimmed the previous year are trimmed back. This maintains a slightly tighter, denser shrub with more branch tips for flowers, but also helps keep the viburnum reduced in size.