Volcano Mulching Kills Trees
Volcano mulching kills trees!
The latest trend in mulching techniques is actually detrimental to trees. It has been nicknamed “volcano mulching” for good reason. Where or how this practice started is uncertain, but the long-term effect is known to be destroying trees in landscapes across America.
Volcano mulching is an improper mulching technique where mulch is piled high against the trunk of a tree. This is often seen in commercial landscapes; look for it the next time you go shopping! It is recommended to avoid this type of tree care maintenance. Mulch should not touch the trunk of the tree. The trunk is simply not meant to be covered, and doing so invites improper root growth, decay and pests; it may kill the tree.
Mulch is supposed to achieve these main goals: retain soil moisture, suppress weeds and moderate soil temperatures. The root zone of an established tree extends beyond its drip line (where rain would drip from leaves at the end of its farthest reaching branches), so mounding the mulch against the trunk does little for the roots, except to cause the roots immediately around the trunk, especially in young trees, to grow into the volcano. Also, the piled mulch softens the bark of young trees and trees with smooth bark, such as maples, and invites insects, rodents and disease to invade. The lower trunk, unlike the roots, cannot survive long term with the constant moisture trapped by the collar of mulch. It is the equivalent of planting a tree too deeply, which leads to demise and ultimately death of the tree.
The roots of a tree find their own level in an attempt to balance the needs of water and air. By piling mulch too thickly above the roots at the trunk, the existing surface roots are suffocated and new ones grow into the mulch. Not only does that leave them at risk of drying and dying when the mulch decays, but also causes them to grow across the stem, potentially strangling the tree to death. This is known as girdling roots.
Proper mulching is very beneficial to trees. Check the existing depth of the mulch around your trees. If 2-4 inches is already there, simply rake to refresh and break up the existing mulch. If not, spread mulch 2-4 inches deep to the drip line of the tree; if possible, do not let the mulch touch the trunk. The mulch should form a flat donut with the trunk in the center. Keep mulch FLAT, not mounded, so that water will not run off. Another guide is the “3x3x3 rule” or 3 inches of mulch, 3 inches from the trunk, in a circle 3 feet wide. Organic mulches (hardwood shredded mulch and wood chips) are preferred over stones or other inorganic mulches. More than 2-4 inches is over-mulching. So, don’t use too “mulch” of a good thing!