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The wide variety of viburnum species and their numerous cultivars all have the same requirements when it comes to pruning. These deciduous and semideciduous plants are not demanding and do not need a regular pruning regimen to remain healthy and produce abundant flowers. Pruning a viburnum is usually only necessary to remove dead or damaged growth or to keep the plant trimmed to a specific size. Using pruning shears with sharp blades will avoid leaving torn or shredded cuts on the plant. Timing is critical when pruning this plant as next year's flowers could be sacrificed if the pruning is done at the wrong time.
There are several circumstances when a viburnum can benefit from pruning. Gardeners should remove dead or broken branches before the vulnerable wood promotes plant disease or encourages destructive plant pests. Pruning diseased branches can help prevent disease from spreading to the entire plant. The removal of weak stems and branches encourages the plant to direct its energy into growing strong, healthy branches. Pruning a viburnum to thin out dense growth allows more air to circulate through the plant, cutting down on the possibility of fungal diseases.
Viburnums bloom on the last year's wood. Pruning established growth risks destroying the current season's flowers, and pruning newer growth risks destroying the following year's flowers. There are two times during the year when it is safe for pruning a viburnum. The first is during the spring, when the flower buds begin to develop and it is easy to see which branches to avoid cutting. The second time is during the summer, immediately after flowering is complete, when the branches that held the flowers can be safely pruned away without endangering the next year's blooms.
When pruning a viburnum, the first step is to remove the dead and diseased branches. Any broken branches or crossed branches that rub against each other are the next to cut. This eliminates the undesirable parts of the plant and opens it up so that it is easier to see if more of the plant needs to be removed. If the plant needs to be thinned, more branches can come out by pruning them away, making sure the remaining branches create a balanced effect. Finally, gardeners can prune the viburnum to size, cutting away the tips of the outer branches until the plant is the desired shape.