Midwinter ideal time to prune most shrubs. Here’s what you need to know.
Midwinter is an excellent time to get outdoors and prune shrubs.
“You can prune shrubs any time, but it’s often easier when they are leafless and dormant,” said Julie Janoski, Plant Clinic manager at The Morton Arboretum in Lisle. “You can see their branching structure without foliage in the way.”
Pruning when shrubs are actively growing often stimulates a burst of disorderly new growth. That won’t happen if you prune while the plants are dormant. Instead, pruning now will direct their growth once the growing season starts.
Because diseases and insects are also dormant in cold weather, winter pruning is less likely to spread diseases or pests. “You still need to practice good hygiene, such as disinfecting your pruners between cuts with alcohol,” she said.
Here are some tips from the Plant Clinic for winter pruning:
Choose what to prune. Midwinter pruning is best for deciduous shrubs, not evergreens. “Wait to prune evergreens until April or so, just before their spring burst of growth begins,” Janoski said.
You’ll also want to avoid winter pruning of shrubs that bloom in spring, such as forsythia, lilac, flowering quince, and viburnum. “These shrubs carry their flower buds through winter, so if you prune them now, you will be removing flower buds that would bloom this spring,” she said. It won’t hurt the plant, but it will diminish this spring’s bloom show. Find a chart that tells when to prune many species of garden shrubs at mortonarb.org/prune-timing. The Plant Clinic can help you identify shrubs.
Use sharp tools. Sharp pruners and saws will make clean cuts that are less likely to admit disease or decay and will seal up more quickly. “It’s also easier to cut when your tools are sharp,” she said.
Keep it natural. Most shrubs look best and will be healthiest if they are pruned selectively with hand pruners, branch by branch, in a way that respects their natural form. Use power hedge trimmers only for formal hedges.
Prune for a purpose. Before you start, think through why you are pruning the plant. “Not every shrub needs pruning at all,” she said. “But if you do prune, your reasons should guide the technique you use.” If you aim to reduce the shrub’s size or just want to tidy up its outline, you may only remove a few branches that stick out. To open up a shrub to air circulation and give it a more graceful form, rejuvenate it by cutting back one-third of the oldest, largest stems near the ground. If the shrub is a dense tangle, you may need to renew it by cutting the whole thing back. Learn more about pruning techniques at mortonarb.org/shrub-prune.
Pause and reflect. Every few cuts, step back and check if you’ve done enough to achieve your desired effect. “It’s possible to get carried away,” Janoski said. If you prune too much, there’s no need to worry, she said: “The plant will nearly always recover in time.”
For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.
