KC Gardens

How to keep your tree trunks healthy

Surrounding trees with mulch helps prevent damage to the trunk from lawn mowers and trimmers.
Surrounding trees with mulch helps prevent damage to the trunk from lawn mowers and trimmers.

The trunk might be the most neglected part of a tree. Leaves get the most attention, followed by the roots. But a trunk should not be taken for granted as it must be sturdy and healthy for the rest of the tree to grow strong.

The trunk provides support for the canopy and, most importantly, the central point that houses the xylem and phloem that connect the movement of water and food for the entire tree. Once a trunk is damaged, it is slow to repair and often is never fully functional. This leads to a decline in the tree’s growth and the beauty of the leaf canopy.

Care during the tree’s life, from planting through maturity, should be about protecting or preventing trunk injury. Unfortunately, the most common injury is inflicted by humans.

Young tree bark is softer, lighter in color and easily damaged by even the slightest abrasion. Damage can occur transporting the tree home from the nursery, letting the trunk bounce on hard surfaces such as a pickup tailgate. It can happen during planting by man-handling.

But the main culprit is lawn mowers and weed whips. It can also be infected by environmental conditions.

Protecting the bark layer should start on Day 1 and continue forever. Prevention is the key; a wound will remain a part of that tree’s structure for its entire life. Rot and decay enter a tree through wounds, leading to a slow and painful death.

Besides the obvious, there are keys to reducing trunk damage.

All trees, regardless of age or size, should be surrounded by mulch. The mulch ring serves several purposes, but in trunk protection mulch keeps grass away from the base, thereby eliminating damage from a mower or trimmer.

Removing grass within 3 to 4 feet around the tree at an early age will double the growth rate of the tree. The ring of mulch should be about 3 inches deep and kept slightly away from the bark layer to reduce rotting conditions.

Young, light-color tree bark common on many species, including all maples, is highly susceptible to an environmental issue that occurs during the winter: sunscald. Sunscald causes the bark to split vertically on the south to west side from the sun exposure on cold days. This is why I’m not a fan of red maples, as it is hard to find a tree that does not suffer from this condition.

While not a guarantee, wrapping the trunk from leaf drop (fall) to bud break (spring) when the tree is young helps reduce the problem.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org or visit KCGardens.KansasCity.com.