Before the holiday bustle becomes all-consuming, consider arranging to have your large trees inspected and pruned this winter.
“It will be easier to reserve the services of a trained and qualified arborist if you book early,” said Sharon Yiesla, plant knowledge specialist in the Plant Clinic at The Morton Arboretum in Lisle.
Having big trees checked every few years and pruned to remove dead or damaged branches is the best practice for trees growing in urban areas. “It can keep our most valuable trees healthy,” she said. A professional arborist can take out any wood that is weak or branches too close to buildings before they become a hazard. Pruning also gives an arborist opportunity to look for signs of disease or insect problems.
Winter is a fine time for tree pruning for several reasons. On deciduous trees, bare branches make it easier for an arborist to inspect the tree’s overall structure and to examine it close-up. Because the trees are dormant, they will not respond to the pruning until spring, when their growth would naturally restart.
Pruning in winter also reduces the chance of spreading insects and diseases. In fact, winter is the only recommended time to prune some species, such as oaks.
“If you prune oaks during the growing season, you risk spreading serious diseases,” Yiesla said. One of the worst is a fungal disease called oak wilt. The oak wilt fungus is spread by a beetle that is attracted to open pruning wounds in trees and carries the spores from tree to tree. Since the beetles aren’t active in winter, the safe period for pruning an oak
is usually between Oct. 15 and April 15, she said.
Oak wilt is difficult or impossible to treat, she said, so the best way to fight it is to prevent it. The most important thing a homeowner can do to protect an oak is to prune it only in winter unless it has been damaged by a storm.
Large, mature trees of any species should only be pruned by certified professional arborists. Not everyone who offers tree care is trained or certified.
“Arborists certified by the International Society of Arboriculture have the right expertise to prune and inspect a tree,” Yiesla said. They also have the training and equipment to work safely and carefully far above the ground.
You can find a certified arborist through the website of the ISA (treesaregood.org/findanarborist) or the Illinois Arborist Association (illinoisarborist.org). Ask to see a certificate of liability insurance before you hire a firm.
Don’t prune a tree yourself unless you can do it with both your feet on the ground. If you would have to climb a ladder to prune a tree, consider calling in an arborist. “It’s easy to get seriously hurt,” she said.
“Always err on the side of hiring a professional and keeping yourself safe.”
It’s not just about the danger that you might fall. Tree branches can weigh hundreds of pounds and can swing unpredictably as they drop. Cuts that are not skillfully made are raw wounds in the wood that can let rot, disease and insects into a tree.
Large trees are especially valuable. They add to your property value and the desirability of your neighborhood. Big trees provide the lion’s share of the other benefits we get from trees, including shade, cooling, pollution control and stormwater management. If a mature tree is lost for lack of care, it can take years or decades for a replacement tree to grow to that size.
“Professional tree care is worth the investment to keep our big, beautiful trees healthy,” Yiesla said.
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.