How much mulch should I use?

We checked in with Raymond Milcsik, a landscape architect with almost 20 years of experience and member of the American Society of Landscape Architects, to see what he had to say about the proper use of mulch.

Mulching is a beneficial practice when done correctly. Proper mulching reduces weeds, helps retain soil moisture, keeps the soil cooler in the summer and warmer n the winter and can improve the soil structure as the mulch breaks down and decays. It can also reduce weeding maintenance andcreates aesthetic value.

The general rule is to apply a 2" to 4” layer, depending on the type of mulch. Finer particle mulches should be applied in a 2" to 3” layer, and larger particle mulches in a 3" to 4” layer. Never apply the mulch up against the base of the plant, including trees.

One of the most common and incorrect practices is over applying mulch and piling it against the tree’s trunk, forming a cone shaped ring. These “mulch volcanoes” (see the photo) can be very detrimental to the health of the plant by creating an environment prone to disease, insects and rodents. In addition to the health problems caused by the mulch being in contact with the bark of the tree trunk, this is one of the primary causes of root growth in a pattern that girdles and eventually kills trees.

A properly mulched tree is one where the base of the trunk (the trunk flare) is visible and the mulch ring extends out to the drip line of the tree as shown.