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Ten Ways to Kill a Tree (or Hasten its Demise)

If you recently planted trees in your landscape, or if you simply love these stately landscape assets, the title may be alarming. I recently wrote articles on tree selection and tree installation around Arbor Day. Those articles outlined best practices to give your trees a better chance of surviving and thriving.

Today’s article concerns ten common mistakes people make when planting and caring for trees. These practices may kill a tree, stress it, or hasten its demise.

  1. Plant your new tree deeply.

By planting too deeply you discourage oxygen from getting to the roots, leading to decline and hastening death. Planting depth is even more important than planting hole width. Find the root flare on the trunk just above the first main root. When properly planted, the flare should be visible above the finished soil grade.

  1. If planting balled-and-burlapped stock, leave all the twine around the tree trunk.

This is a surefire way to girdle the tree in a few short years by choking off water- and food-conducting tissues, effectively severing the connection between roots and crown. Obviously, you must remove all twine from around the trunk.

  1. When planting a tree from containerized stock, especially trees that have been in the container a long time, do nothing about the circling roots.

Recent research suggests that a “boxing” treatment of the root ball, cutting the outer 1” in four cardinal directions with a saw, will encourage roots to grow laterally. Otherwise, they may continue to grow in a circle and eventually become girdling roots, likely leading to tree death.

  1. To put an exclamation point on your planting operation, mound up mulch like a volcano around the trunk. Your neighbors will be so impressed!

“Mulch volcanoes” encourage adventitious roots to form where they were not designed to be, create a favorable environment for voles to burrow through and gnaw on the trunk, and provide a moist environment suitable for insect borers and/or diseases to get a foothold. Don’t mound any mulch against the trunk – maintain an air gap of 2-3 inches with no mulch, and only mulch 2-3 inches deep around the root zone.

  1. Create a raised flower garden around the trunk of your tree. For an added accent, install a circular hardscape structure like stone, brick, or cinder block up 2 feet or so and fill in around the trunk with soil for the flowers.

This is a terrible idea in relation to the tree’s health. Many of the items mentioned under the “mulch volcano” above are probable.

  1. Do some construction around your tree – change the soil grade, install a water line and sever several roots in the process, and compact the soil as much as possible. For added effect, bump into trees with equipment a few times.

Ok, I admit we’re getting a bit tongue-in-cheek here. Soil and root system changes like these can have profound effects on landscape trees. Try to limit these practices as much as possible around home site trees you plan to keep. Bumping into trees with equipment can damage the cambium layer, described in more detail in the next item.

  1. Mow so close to your trees that the mower deck rubs off the bark. Alternatively, the same can be accomplished with a weed-whacker. After all, you are after every single blade of grass, right?

Normal mulching around the root area, as described in #4 above, is a good idea and will also discourage over-zealous mowers or string trimmer operators from getting too close and damaging the base of your trees. This practice permanently damages the cambium, or growth layer, of the tree. There is no “cure” for this damage.

  1. Top your tree. All those branches may fall someday.

Topping or annually “shaping” your tree is an effective way to hasten the tree’s death. It encourages vigorous new branches with weak attachments and facilitates decay. So, don’t top trees. Remove truly problem branches in a “surgical” way using properly made pruning cuts.

  1. Kill weeds in a fence line near trees with a soil sterilant so you’ll never have to mow along the fence again.

This is another terrible idea. Soil sterilants kill weeds for multiple years, and they stay in the environment for a long time. They can kill trees when roots absorb enough of the herbicide to be fatal. Tree roots can grow as much as 2-3 times the height of the tree in any one direction.

  1. Let bagworms go wild on pines, spruces, and other conifers.

Bagworms are individual caterpillars inside a silken bag covered with plant material, so they look somewhat like a pine cone hanging from a branch. In a short time, they can defoliate conifers, and trees may eventually die. Inspect your trees for pests of all kinds, and use proven integrated pest management [IPM] practices to combat pests.

For more information, access Purdue Extension’s publications entitled, “Why is My Tree Dying?” and “Mechanical Damage to Trees: Mowing and Maintenance Equipment,” at Purdue Extension’s Education Store, You may also find information on planting and pruning landscape trees at the site, including helpful videos.

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