10/18/2022 - Mulching 101: A Tree’s Best Friend, or Enemy

Mulching is one of the easiest applications residents can do, to protect trees. The choice of mulch and the overall application is important to the health of the tree. Mulch can be a layer of any substance, organic or inorganic, applied to the base of the tree, forming a flat donut shape with the tree trunk in the center. An easy guide to follow is the “3 x 3 x 3 rule,” which is 3 inches of mulch, 3 inches from the trunk, in a 3-foot wide circle.

Benefits of proper mulching technique:

  • Reduces evaporation from the soil surface. May lower water use by up to 50%. Stabilizes soil moisture.
  • Promotes microorganism activity and improves soil condition.
  • Keeps soil temperature consistent by insulating against cold and heat.
  • Prevents soil compaction and erosion.
  • Aesthetically enhances landscape appearance.
  • Protects against mechanical damage by creating a protective space that keeps mowers and trimmers away from the trunk.

Types of Mulch

Mulch can be organic or inorganic. Inorganic mulches include various types of stone, lava rock, pulverized rubber, textile materials and other materials. Inorganic mulches do not decompose and do not offer many benefits to improving soil conditions. Organic mulches include wood chips, pine needles, hardwood or softwood bark and compost mixes, usually derived from plants. These mulches will decompose and help improve soil conditions and fertility. Because of this, organic mulches are the choice of many arborists and landscape professionals.

“Volcano” Mulching – When Mulch Becomes the Enemy

As beneficial as mulch is, too much can be extremely harmful. Mulch, when incorrectly applied, will contribute to the decline of trees. The most common example of this is “volcano mulching,” an improper technique where mulch is piled or mounded right up to the tree trunk, often with a depression at the top that will collect water.

 Volcano mulching can cause:

  • Disease and decay due to moisture retention at the trunk
  • Insect damage
  • Rodent damage
  • Girdling roots
  • Conditions that may be too damp or too dry for the root system as water cannot penetrate the thick layer of mulch
  • Unable to develop proper root flare to stabilize the tree.
  • You should always be able to see the trunk and the root flare of a tree.

For more information regarding tree-related issues, contact the Tree Warden or the Forestry Committee.