Winter is a fine time to prune deciduous shrubs. When the leaves are gone, you can see the true form of the plant to help you choose which branch to cut. How you prune will depend on each shrub’s situation.
Selective pruning: If your goal is to control the size of a shrub, balance its shape, remove dead or damaged wood, or open it up a bit, take it branch by branch. Using clean, sharp bypass pruners, cut just above the place where one stem branches off from another. Pause often and step back to consider the effect of your pruning so far and whether you’ve done enough.
Renewal pruning: If a shrub is thickly overgrown, you can clear it out and renew its vigor in stages. Each year, cut out some of the oldest, thickest branches down to the ground, removing about a third of the plant. In spring new stems will sprout and in three years the whole plant will be renewed. Cut the older branches as close to the ground as you can, he says, using clean, sharp bypass pruners or a pruningsaw. Distribute your cuts around the plant, rather than concentrating on one area.
"At the end of three years, you'll have removed the entire plant, and it will all have been replaced with new growth," says Patrick Kelsch, collections supervior. You remove only one-third of the plant each year, so "you're not going to create a gaping hole in the landscape," he says.
Rejuvenation pruning: If a bush has become dauntingly huge and dense, drastic action may be called for. Most deciduous shrubs can be entirely cut back to within an inch or two of the ground in late winter.
Rejuvenation works best on species that grow vigorously, such as deutzia, dogwood, forsythia, smooth hydrangea and spirea, Kelsch says. Slower-growing shrubs, such as lilac, viburnum and chokeberry, are better tamed with renewal pruning.
New growth will start in spring and in a couple of years the shrub will be back at a good size. Then you can keep it under control with regular selective pruning.