Shrubs can still be pruned once spring growth begins. It’s a good time to evergreens and remove dead branches that have been killed over the winter. (Beth Botts/The Morton Arboretum) - Original Credit: Beth Botts/The Morton Arboretum (Beth Botts / HANDOUT)

Now that leaves are opening on your shrubs, is it too late to prune? Not at all, said Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle.

“We often suggest pruning trees and shrubs in the winter, when they are dormant and don’t have leaves, because the bare branches make it easier to see what you’re doing,” she said. “But you can prune shrubs almost any time of the year.”

Plants will react differently to pruning in spring, when the sap is flowing and they are actively growing, than in winter, when they are largely shut down. “Spring pruning can stimulate a surge of growth, which can lead to a need for more pruning later on,” Yiesla said.

That increase in growth is useful if you have formal hedges or shrubs that you shear with an electric hedge trimmer. “Formal hedges are best sheared while they are actively growing in spring, so the plant can recover from the many cuts,” Yiesla said.

Evergreens, too, should be pruned in spring, ideally just as their active growth starts. Since evergreens do nearly all their growing in spring, it’s the only time they can recover from pruning by filling in with new growth.

When you see brown branches on an evergreen shrub or tree, it likely means the needles or leaves have dried and died over the winter. “If the branch is obviously dead, prune it out,” Yiesla said. “But if there’s any hint of green, leave it alone for a few weeks and see if it recovers.”

Pruning may be required on deciduous trees and shrubs if branches are broken or dead. “All shrubs accumulate dead wood over time,” she said.

To tell whether a branch is dead, gently nick the bark with your fingernail or the back of a pruner’s blade. On a live branch, you’ll be able to see a green layer just under the bark. Dead wood is dry and brittle and its bark may be darker in color than live wood.

You may also want to prune a shrub to tidy it or control its size. Prune one branch or stem at a time, down to the ground or to a place where a branch is connected to a main stem. “With leaves on the branches, it may be more difficult to see the shrub’s structure,” Yiesla said. “You may have to feel your way. Go slowly and step back often to see how you’re doing.”

Wait to prune trees and shrubs that bloom in spring, such as forsythia, lilac, crabapples, and viburnums, until they have finished flowering.

If you prune in springtime, it’s especially important to disinfect your pruning tools because they can easily carry insect eggs or disease pathogens between plants. A new wound in an actively growing plant is an open door for infection.

Some professionals carry a container of 70 % rubbing alcohol to dip their tools into, and others put the alcohol in a small spray bottle. “Ideally you would disinfect the tool after every cut,” Yiesla said. “At a minimum, disinfect them before you move to a new plant.”

Some trees, such as maples and birches, may bleed sap if they are pruned in spring. “It’s unsightly, but it’s not harmful,” she said.

Disease is the reason oak and American elm trees should never be pruned during the growing season. “There are deadly diseases that enter oaks and elms through open wounds,” she said. Except in emergency circumstances, such as storm damage, wait until next winter, when trees are dormant, to prune these species.

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.