Mulching can be one of the best practices for ensuring your tree’s health, but if done incorrectly, it can also be one of its biggest threats. The Oak Creek Forestry Division wants you to learn why mulching is good for trees and the proper techniques to help your tree thrive!

Proper Mulching Method

When it comes to mulching, it's best to opt for organic materials due to their beneficial impact on the soil. One excellent and affordable choice is hardwood bark, particularly when it contains a combination of bark, wood, and leaves.

You can apply mulch to landscape trees throughout the year, but the optimal time is in the middle of spring when the soil temperature has warmed enough for root growth to commence.

Cover as much area as possible with mulch, extending it to the outermost edge of the tree's canopy, known as the "drip line." Keep in mind that as the tree grows, the drip line expands.

A layer of 2 to 4 inches of organic mulch is ideal but adjust accordingly if the soil has poor drainage. Avoid exceeding 4 inches, as this can harm the tree's root system. Finely textured or double-shredded mulch allows less oxygen to reach the roots, so in such cases, limit the layer to 1 to 2 inches.

Things to Avoid

“Volcano” mulching is when mulch gets piled high against the trunk of the tree and should be avoided. To promote tree health, ensure that the mulch material does not come into contact with the trunk. Allow the root flare, where the trunk meets the soil, to be visible. This area, marked by a noticeable swelling in the tree's trunk and a bell-like shape, signifies where the roots start spreading outward. The correct way to place the mulch is by creating a bowl shape with the low area around the trunk.

Over-mulching can lead to detrimental effects such as root starvation, trunk rot, disease, insect infestation, rodent damage, and the development of girdling roots. Over time, these issues can slowly cause the tree to die.

Using rocks as mulch around trees is not recommended. While rocks may provide a decorative touch, they tend to absorb and retain heat, resulting in quicker drying of trees and plants, necessitating increased watering for survival. Additionally, rocks can migrate into your yard and potentially damage your mower.