How to Hard Prune a Viburnum
To a novice gardener, it might seems sacrilegious to chop off a plant’s budding branches or just-spent flowers, but if you want the plant to thrive as a lush element in your landscape design, a good pruning keeps it in line. More than 150 species of viburnum (Viburnum spp) grow in the U.S. Department of Agriculture plant hardiness zones 2 through 9. They’re ideal for filling in problem spaces within your garden. They can be controlled easily by soft and hard pruning, both of which are necessary to prevent a leggy look and having the plant spread throughout your landscape.
Deciding When to Prune
Young viburnums don’t need pruning unless they seem to be growing out of control and invading the nearby plants. You may want to shape your young shrub with a light prune just after its first flowering. You’ll find that after pruning, your plant is flush with new growth. An old viburnum that’s overgrown its share of the garden and has become leggy doesn’t contribute to the overall look of the landscape. Don’t pull it out and trash the plant; instead, revive it with a hard pruning.
Timing Is Key
Viburnum develops its buds the year before they flower. Pruning buds destroys the flowers. Prune just after the flowers wilt by cutting back the flower heads and correct any misshaping by cutting the branch back so that the newly sprouting leaves are visible. Energy is then directed toward the formation of new growth, which you’ll be able to enjoy the following spring.
As you prune, be aware of any buds on the branch. Prune about ¼ inch above the bud to protect it for the following year. If you enjoy watching the wildlife that viburnum fruit attract, wait until the fruit develops after the flowering period. Prune after the fruit has fallen or been eaten.
Use the Right Tools
Hand pruners are good for branches up to ½ inch in diameter. Be sure they’re sharp and wipe the blades with alcohol prior to each cut to prevent insect infestation. Make a clean cut on a diagonal and remove the debris. A larger pruner, such as a pair of lopping shears, has a long handle, giving it leverage for branches over ½ inch. They provide a clean cut, but keep a sharp knife handy to clean up any ragged edges. Many hard prunes are for branches larger than 1 inch, which call for pruning saws. The prominent teeth are designed to prevent the sap from gumming, and the cut is achieved as you pull the saw toward you.
Hard Pruning’s Three-Year Plan
A serious hard prune is in order when your viburnum looks like a stack of twigs growing vertically. But it can’t be done all at once. Hard pruning for rejuvenation is completed in a step plan in one-year increments and achieved over three years. Late winter or early spring, depending on local weather conditions, is the time to start hard pruning.
- The first year, cut back one-third of the large, old branches to just about a few inches from the ground. Space the cuts evenly across the width of the viburnum. Check for dead or damaged branches and remove them as well. During the year, remove any little suckers that sprout from the branches.
- The second year, do the same with another third of the branches. Note the new branches forming at ground level. They will ultimately fill in the vacant spaces in the viburnum, creating fullness.
- By the third year, your viburnum should be on its way to becoming the lovely, flowering shrub it was meant to be, with just one more hard prune required. After the hard pruning is complete, maintain the viburnum with regular simple pruning just after it flowers.
Pruning Rejuvenates Old Viburnum
Never fear cutting a viburnum. Even if you prune in the wrong season, you won’t kill the plant. You may miss a season of flowering, but the following year, it’ll be rejuvenated and back in its glory, filled with white and pink flowers that decorate your landscape.
- Hard pruning of viburnums is also commonly done in late winter or early spring while the plant is still dormant, but waiting until after the flowering period inhibits the growth of straggly water sprouts in favor of healthier, more substantial new branches.
- Total removal of old growth is not always necessary. Cancel subsequent thinning of old growth when you are satisfied with the appearance of the viburnum.
- When a saw is required for thick branches, choose a curved saw to gain easier access to branches in dense shrubs.
- Viburnums generally require very little pruning, but hard pruning may be necessary if the growing area is too small for the species or if the plant is old and lackluster.
- Renewal pruning is the process of removing old branches near ground level to produce new growth. This three-year practice of removing old branching by thinning similarly encourages new growth and is preferred for viburnums because the gradual process is less shocking than complete removal.
A versatile writer, Jann enjoys research as well as doing the actual writing. A career in television writing, as a magazine editor and celebrity interviewer, Jann adapts to her environment, having traveled the world, living overseas and packing and unpacking her treasures for a new location over 30 times.