Mulch: The Simple Secret to Healthier Trees and Beds

If there's one thing you can do today to improve the health of your trees and landscape beds, it's proper mulching. Mulch is simple, inexpensive, and delivers outsized benefits when applied correctly. Unfortunately, improper mulching (especially the dreaded "mulch volcano") is one of the most common landscape mistakes we see.

Benefits of Proper Mulching

A two to three inch layer of organic mulch over the root zone provides multiple benefits: it conserves soil moisture by reducing evaporation, regulates soil temperature (cooler in summer, warmer in winter), suppresses weed growth by blocking light, adds organic matter to the soil as it decomposes, reduces soil compaction from foot traffic and rain impact, and protects trunk bases from lawn mower and string trimmer damage.

The Right Way to Mulch

Apply a two to three inch layer of organic mulch (wood chips, shredded bark, or composted leaves) in a wide ring around the tree. The mulched area should extend as far as practical, ideally to the drip line or beyond. Pull mulch back two to three inches from the trunk so it does not contact the bark. The finished profile should look like a donut, not a volcano.

The Mulch Volcano Problem

Piling mulch against the trunk (the "volcano" shape) is harmful because it keeps bark constantly moist, creating conditions for fungal infection and decay. It can cause adventitious roots to grow into the mulch instead of the soil, creating a girdling root problem. It provides habitat for rodents that may chew bark. And it hides signs of trunk damage or disease from view. If your trees currently have mulch volcanoes, pull the mulch back to expose the root flare, the point where the trunk widens as it meets the soil surface.

Best Mulch Materials

Arborist wood chips (the mix of wood, bark, and leaves produced by tree care operations) are among the best mulch materials available. They decompose at a moderate rate, support beneficial soil fungi, and provide excellent moisture retention. Avoid dyed mulches (the coloring agents can affect soil chemistry), rubber mulch (provides no soil benefit and can leach chemicals), and fine-textured mulches that mat together and repel water.

On commercial properties, bed refreshes are part of our commercial grounds maintenance and landscape enhancements work. Not sure whether your current mulch is helping or hurting? Use our Ask an Expert form.