Mulching is one of the most beneficial things a homeowner can do to keep trees healthy. It makes growing situations more “friendly” for trees in general.
The generally recommended mulching depth is two to four inches, according to the ISA. When applied properly, mulch helps maintain soil moisture, control weeds, improve soil structure, and inhibit certain plant diseases. Mulch also protects plants and trees from “weed whacker” damage and “lawnmower blight” in addition to giving planting beds a uniform, well-cared for look.
Urban landscapes are typically harsh environments with poor soil conditions, little organic matter, and big fluctuations in temperature and moisture – all “unfriendly” growing situations for trees. A two to four inch layer of organic mulch can mimic a more natural environment for trees and improve overall plant health.
When mulching, Skiera says it is important to remember that the root system of a tree is not a mirror image of its top. “The roots of most trees extend out a significant distance from the trunk. Also, most of the fine absorbing roots of trees are located within inches of the soil surface.”
These shallow roots are essential for taking up water and minerals for trees, and they require oxygen to survive, Skiera says. A thin layer of mulch, applied as broadly as practical, can improve the soil structure, oxygen levels, temperature, and moisture availability where these roots grow.