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Mulch Around Trees… Do I need it?


Proper mulching is one of the most beneficial practices that can be done for the health of a tree if it is done correctly. If not done correctly, mulching trees will suffer from fungus, rot and decay and even early tree death when mulch is incorrectly used.

There are many benefits of using mulch besides having a well-groomed landscape. Organic mulching:

  • Improves soil structure
  • Increases infiltration
  • Reduces soil moisture evaporation
  • Boosts soil microbes
  • Moderates soil temperature
  • Limits weed competition
  • Reduce soil compaction. 

Many professional landscapers use a “volcano” method of mulching around trees. Volcano Mulching is an improper mulching technique where mulch is piled high against the trunk of a tree. While this may be aesthetically pleasing, this technique will attract fungus, rot and decay and ultimately lead to the tree’s death. It can also cause girdling root.

Girdling root is the process when the roots of a tree or plant begin to grow in a circular pattern causing the roots suffocate itself.  It is called “The Silent Tree Killer” for a reason.  You may not notice an issue for years… Then when damage is noticed, its usually too late to save the tree. Girdling root can happen naturally, but is most common from improper planting techniques. As seen in the images below, girdling root typically happens when a tree is planted too high or has a constricting edging/barrier of some sort. The roots search for water and grow, but they have nowhere to spread. Eventually the roots grow in a circular pattern around itself resulting in suffocation. Below are examples of girdling root. 


The mulch was pulled back to show the exposed roots growing in a circular pattern.
You can see the black edging has prevented the roots from expanding causing the tree to choke itself.


The proper technique is to cover the area around the tree in 2 to 4 inches of organic mulch. Do not place mulch directly against the trunk of the tree. Direct contact between mulch and tree trunk/bark may lead to bacterial or fungal infections. The trunk flare is the lowest part of the trunk and should be exposed to air. A wide mulch ring is desirable, a deep one is not. The actual size of the area to be mulch depends on the size of the tree. Mulch rings should be at least 6 feet in diameter. For more tree planting info check out this site: https://www.arborday.org/trees/planting/  



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