December 28, 2018 by
Photography by Bill Sitzmann

Trees require maintenance or they can depreciate a property. Knowing when and how to trim them is critical. (It is important to note that this article discusses landscaping trees, whether deciduous or coniferous. Fruit trees require special pruning methods.)

First, tree owners should recognize that trimming or pruning trees harms them. A tree is a living, breathing organism. “Every time we prune, we are wounding a tree,” says Scott Evans, an arborist with the Nebraska Extension in Douglas and Sarpy counties. “Every cut needs to have a purpose.”

Evans says that science once recommended trimming trees in the winter, but now recommends spring as the optimal time for tree maintenance.

“One of the first publications which talked about changing the time was 2004,” he says. “It was published in European Forestry Resources. It was kind of slow to catch on over here. I first heard about these pruning practices in 2015.”

Evans says the new best practice is to avoid trimming most trees in the winter, when the cold affects a tree’s growth. New science says the active spring growth helps the tree recover from the damage caused by cutting.

“We want to have those cells actively growing so they can start sealing as soon as possible,” he says.

The method of cutting is also important. “A good clean cut really allows the tree to respond quicker to the healing process,” Evans says.

Evans recommends pruning only for reasons of safety or a tree’s health. Dead or damaged branches should be managed so they don’t fall off the tree. Falling branches can hurt people, property, and the tree itself by ripping off the bark. When bark falls off, it cannot grow back. The water-conducting tissue that lies directly below the bark could then be damaged when a limb falls off, meaning the portion above the damage may not get the water it needs.

Branches that are crossed or rubbing should also be managed, Evans says, as they will eventually grow into each other, which can create a point for bacteria and decay to harm a tree. Likewise, rubbing creates an entryway for decay-causing organisms.

There are, however, a couple of reasons to trim trees in the winter. Evans notes that a major ice or snow event can damage branches, and those damaged branches should be managed as soon as possible, as further weather events could cause more significant problems. Evans says safety concerns, such as limbs hanging over houses and driveways, should also be immediately addressed in the winter.

There are two varieties of trees that still should be trimmed in the winter: oak, which is susceptible to oak wilt; and elm, which is susceptible to Dutch elm disease. Both diseases are transmitted to the trees via different types of beetles, which are attracted to fresh cuts on these trees. “Trim while the beetles are not actively out and about,” Evans says of oak and elm trees.

And homeowners trying to trim their own trees should keep their personal safety in mind at all times.

“If you have to lift a chainsaw over your head—call an arborist,” he says, noting that tree trimmers can do serious damage to a tree—or themselves. Additionally, having clean tools prevents transmission of disease. Evans recommends sanitizing cutting tools with a solution of 9-parts water to 1-part bleach.


Visit extension.unl.edu for more information.

This article was printed in the January/February 2019 edition of OmahaHome. To receive the magazine, click here to subscribe.

Scott Evans