Arboricide: The Tree-Killing Mistakes of Well-Intentioned Landscapers

In Possum City by Eleanor Scottleave a COMMENT

The grassy medians in the East Knoxville Target parking lot are planted with small maples and oaks. The grass is neatly trimmed and each tree has a tidy cone of dark mulch packed around its trunk. At first glance, it looks like an ideal parking lot, like an architect’s CGI rendition of a utopian shopping center, one that attains “green” goals without requiring us to give up our cars.

If you take a closer look, you will see long vertical wounds in the bark of these young trees and the exposed wood rotting at the base. If you kneel down beside a tree and scrape back the mulch, you will find thin false or “adventitious” roots growing from the trunk just under the surface. Some of these roots are beginning to wrap around the trunk.

This tidy cone of mulch is the dreaded “volcano mulching,” a practice of uninformed landscapers that is responsible for weakening and killing the very trees it is meant to nurture and protect.

According to a Target manager, the parking lot landscaping is contracted out by the corporate owner of the strip mall in which the Target is located. He didn’t know the name of the company used, or who specifically is responsible for hiring them. Due to their mulching game, we can infer the landscapers are not professional arborists.

Before Mayor Madeline Rogero hired arborist Kasey Krouse in 2012 as Knoxville’s first urban forester, the city was killing its trees with volcano mulching.

Krouse explains that the hill of excess mulch piled against the base of a volcano-mulched tree causes the growth of adventitious roots that encircle or “girdle” the trunk.

“Girdling roots restrict the flow of water, nutrients, and sugar from moving up and down in the tree vascular system, stressing the tree and, oftentimes, killing the tree,” Krouse says.

He adds that mulch retains heat and moisture, benefiting the root system. But volcano mulching fosters the growth of decay fungi at the trunk and prevents the tree from hardening off before the winter freeze, causing the bark to split.

As for the trees in the Target parking lot, Krouse says the splitting of the bark can be caused by different factors. It may have been caused by improper mulching, or the trees may have been planted too deep, a situation that also creates girdling roots.

“Trees can recover from the effects of improper mulching, but the excess mulch needs to be removed and girdling roots often need to be pruned,” Krouse says.

Krouse says his urban forestry crew is working with city horticulture manager Mark Wagner’s crew to rectify the effects of improper mulching of the city’s trees by raking back old mulch piles and pruning roots. Most importantly, Krouse and Wagner have trained the crews on the correct way to mulch trees, leaving some space near the trunk.

Now that you, too, know about these devastating effects, you may never again be able to walk by a parking lot tree erupting from a volcano of mulch without dropping to your knees and clawing back the pile.


Thanks to longtime underwriter Cortese Tree Specialists, all WUOT listeners know “Tree topping hurts one of nature’s classical performances.”

How does tree topping hurt?

“Topping of trees is done by non-professional tree cutters,” Krouse says. “Tree topping leaves large wounds, which decay the tree. Trees that are topped have a shorter life expectancy and will often become more susceptible to breaking. [They] will spend a lot of resources in growth to make up for the lost tree canopy. This growth is in the form of tree sprouts. As these sprouts get larger, they are more prone to breaking from wind, snow, or ice than if the original branch was left to grow. In order to prevent this, tree owners will often top trees several times, which ends up costing more.”

Why would anyone maim their trees this way?

“Tree cutters will often employ fear tactics when trying to sell tree-topping services, telling people that topping the tree is the only way to prevent the tree from falling or causing property damage,” Krouse says.

Krouse recommends the website for solid tree intel and encourages people to seek a professional arborist for tree work on their property.

Eleanor Scott's Possum City explores our urban forests, gardens, and wild places, celebrating the small lives thriving there. A freelance writer and columnist, she also maintains the Parkridge Butterfly Meadow in East Knoxville.

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