The Best Time to Prune Snowball Bushes

Snowball Bushes

• Various large, spring-flowering viburnums go by the common name "snowball bush," including Chinese snowball, Japanese snowball, fragrant snowball and snowball viburnum. Snowball bushes produce snowball-like round clusters of flowers at the ends of long, arching stems. Tiny individual flowers within these clusters are generally sterile and don't produce berries like other viburnum varieties. Snowball bushes are easy-care, low-maintenance shrubs that generally do best in full sun and moist rich soils, although snowball viburnum can be quite drought tolerant once mature. In climates with hot summers, try to provide some afternoon shade.

Tidying Up

• Prune out damaged, dead and crossing branches when you notice them -- preferably before summer -- cutting them back all the way to the ground. Make less severe strategic cuts -- to improve the plant's shape -- at any time, so long as you remember you're sacrificing some of next year's bloom. Avoid tip pruning or shearing at all costs, however. Later in the growing season such tidying-up will remove flower buds -- and very late in the season it will stimulate stem growth that may not harden-off before winter. But shearing plant tips is a problem even early in the season because it promotes weak stem growth and shading-out of other vegetation.

Routine Renewal

• Regulate the height and spread of your snowball bush with a regular program of selective pruning and thinning each spring, immediately after blooming ends. Cut back about 1/3 of the stems each year, heading back to a branch or outward facing bud 2 to 3 feet above the ground. Remove the oldest, thickest and woodiest stems as much as possible as you shape your snowball bush to achieve an attractive form. Leave medium-sized and new stems, which will be sturdy enough to hold even heavy flower clusters the following year. New shoots will also develop from the stubs of canes you removed.

Total Renewal

• If an overgrown plant needs to be completely "renewed" due to legginess or overall bad form, you can hack the plant back all at once. The Sustainable Gardening (SG) website recommends this approach, following the lead of hardy shrub expert Michael Dirr, author of "Viburnums: Flowering Shrubs for Every Season." According to SG, after your snowball finishes flowering, cut back all stem to 2 or 3 feet above the ground. Your shrub may take two seasons to regain its original height, but it will essentially "start again" with a better, more compact form. Selective pruning and thinning every year will maintain that form.