Laying mulch around trees

Mulching is a great way to keep your trees healthy and strong. As mulch breaks down over time, it adds organic matter back into the soil and improves overall soil health. This encourages beneficial microorganisms, improves soil structure, and supports healthier root development. A well-mulched tree often grows stronger, handles stress better, and looks healthier year-round. 

But if done wrong, your aged mulch may do more harm than good.

Mulching a tree the wrong way can cause serious health problems and may shorten the tree’s lifespan. One of the most common mistakes is piling mulch directly against the trunk, often called a “mulch volcano.” This traps moisture against the bark, which can lead to rot, fungal disease, and insect problems. The trunk flare should always remain visible and free from mulch.

Applying mulch too deeply can also damage roots. Thick layers of mulch reduce oxygen movement into the soil and may hold excessive moisture, creating poor conditions for healthy root growth. In some cases, roots begin growing upward into the mulch layer instead of spreading properly through the soil, which can lead to weak, girdling roots that strangle the tree over time.

Using the wrong type of mulch can create further issues. Fresh green mulch can generate heat as it decomposes damaging roots, while compacted mulch can repel water instead of absorbing it.

How to Lay mulch around trees?

To mulch a tree properly, spread a layer of mulch around the base of the tree in a wide ring, ideally out toward the drip line, at a depth of around 75–100 mm. Keep the mulch pulled back from the trunk by several centimeters so the root flare remains visible and the bark can stay dry. Use aged organic mulch such as arborist wood chips, and keep the layer even rather than piling it up. Correct mulching helps retain moisture, suppress weeds, regulate soil temperature, and improve soil health as it breaks down.