By Marty Ross
Shrubs are the hardworking heart of beautiful gardens in the Midwest. Many great shrubs thrive in our climate, and taking care of them is easy. Spring is the time to brush up your pruning skills.
Copying the pruning jobs you see outside banks, fast-food restaurants, and other corporate landscapes isn’t the best way to learn about pruning, says Chris Romer, a certified arborist and owner of Treecology in Minneapolis. “The predominant method I see is guys shearing everything at the same time, whether it is the right time or not,” says Romer, who’s been in the tree- and shrub-care business for 20 years. He likes to talk about a pruning method he calls “the urban compromise,” to discourage uninspired and unnecessary pruning.
Romer’s method involves studying the shrub’s natural size, growth habits, and flowering period (if it is a bloomer). Often the critical thing is where the shrub is planted. Spots for viburnums, red twig dogwoods, lilacs, and other shrubs sometimes are too small to accommodate the mature sizes of the plants. You have to prune them to keep their growth within bounds.
In general, before you grab your loppers or hedge shears, think about the ways shrubs contribute to your garden. Some of those plants are prized for their spring blooms, some as summer screens, some for berries and fall color.
Instead of simply whacking shrubs to fit the allotted spot, Romer suggests using a light hand and a thoughtful approach. “I’m anti-shearing,” he says. “Too many shrubs are victims of hedge trimmers.”
Don’t just prune from the top, he says. Taking out old stems at the base of a lilac or red twig dogwood invigorates the plants. Lop out crowded growth in the center too. Then take a little off the top, if necessary. Try to preserve the plant’s natural shape.
Modern mop-head hydrangeas (‘Endless Summer’ and others) bloom on old and new wood, and pruning them is more like deadheading. “It’s more like roses,” Romer agrees. You may not wish to cut off spent flowers; hydrangea blooms fade gracefully, and you may not mind them at all. Trim them as they fade, or snip off the old flowers once a year. Look at your garden, not at the calendar: The best time to do this kind of pruning is just before the plants leaf out in spring.
Generally it is safe to prune spring-flowering shrubs, such as forsythia, after they bloom. Cut back forsythia as its flowering period ends. Remove stems that are too long or drooping, and take out some of the oldest branches at ground level.
Hard, midsummer pruning of viburnums may remove developing berries that you and birds appreciate in fall. Prune viburnums in early spring instead.
Severe midsummer pruning also removes a lot of leaves, which stresses plants and may deprive you of the pleasure of a blaze of fall color. A quick, light pruning is better for summer-blooming spiraea than a hard shearing to maintain a tight bun shape, Romer says, and it may encourage another round of blooming.
Proper pruning is a bit of a learning process. Over the years I have learned not to prune the boxwoods in my garden too early in spring or too late in fall. It may feel good to do the work, but it stimulates new growth that may succumb to frost. If the shrubs need it, I prune them in mid-spring or midsummer.
My favorite way to go about pruning is to apply the old saying “Wander, ponder, and prune.” Make a few cuts, then step back. Study the effects as you go. Never cut too much at one time. To make the kindest cuts, take it slow.