The Impact of Mulch Close to Tree Trunks

Distance from Trunk

• As a general practice, mulch should be maintained at least 3 to 5 inches away from the trunk of a young tree and 8 to 12 inches away from older trees. In most cases, it should be spread on the ground to the outer reaches of the canopy or branches. This practice can be of assistance in maintaining moisture in the ground during dry periods, while keeping grass and weeds from growing too close to the trunk and root system.

Root Rot

• Improper mulching can seriously damage any species of tree or shrub. Piling mulch high against the trunk or stem can result in the development of root rot, a potentially lethal problem. Piles of mulch force the soil to retain an excessive amount of moisture and deprive the roots of oxygen, while the water-logged roots suffocate and rot. Depending on the species of tree, the first symptoms of root rot may not display for three to five years or more.

Photosynthesis and Heat

• Too much mulch hinders the ability of the tree to transfer oxygen and carbon dioxide between the roots and branches of the specimen, resulting in damage to the inner bark tissue of the tree. Photosynthesis cannot be properly conducted, and the tree will slowly die. Additionally, piles of mulch around the tree will decay, producing an intense, compost-type of heat that can reach as high as 140 degrees Fahrenheit, enough to directly kill young trees.

Rodents and Disease

• The development of fungal and bacterial canker diseases is encouraged when too much mulch is present around a tree. The moisture that is retained in a bunch of mulch is an ideal hiding place for these fungi. A thick layer of mulch is also a perfect spot for chewing-rodents like mice to hide from predators and live while they feed on the bark of a tree. To avoid damaging a tree with too much mulch, gardeners must research and understand the quality of soil drainage and the root system of the species of tree in question.