How to Mulch a Tree
One of the most common mistakes is arranging the mulch ring around the tree in the shape of a volcano instead of a doughnut. Mulching against the tree trunk can lead to trunk problems, disease problems, habitat for rodents, and excessive soil moisture and root rots.
The benefits of mulching are numerous: helps maintain soil moisture, helps control weeds, keeps lawn mowers and string trimmers at bay, easier maintenance, appearance and improves the soil.
A number of things can be used for mulch. Most commonly used are bark chips, wood chips, composts and pine needles.
The best way to mulch is using a two to four inch layer of mulch. Then be sure to mulch a large area.
Patrick Byers, horticulture specialist, University of Missouri Extension
Recycled Rubber Mulch Tree Ring Mat