Whether you have a newly planted tree or a mature tree in your landscape, laying down a thick layer of mulch is a wonderful yearly practice that can dramatically improve the health of your tree long term.

When you’re planting a new tree in your yard your first step is to choose the right tree for the location, the second step is to plant it correctly, the third step is water it regularly and the final step is to spread mulch around the tree. Older trees can also benefit from a layer of mulch around their base.

In this article you’ll learn the many benefits of mulching, best practices for putting mulching around trees, the best types of mulch to use and where to source it. Oh, and how to avoid mulching volcanoes!

Benefits of Mulching Around Trees

Next to watering, mulching is arguably the best practice for keeping newly planted or even older, established trees healthy long term. 

What is mulch? Mulch is an organic material spread on the soil surface to protect the soil and tree roots from from things like heat, cold, and drought. As it breaks down mulch also improves the soil around the tree.

Mulching benefits include:

  • Decreased evaporation: Covering the soil helps it retain more moisture for the roots to uptake.
  • Root insulation: A layer of mulch moderates the temperature of the roots, keeping them cooler in the summer and warmer in the winter.
  • Air exchange: Mulch allows for more gasses to reach the roots, which improves respiration.
  • Improves soil structure: Mulch breaks down slowly over time and becomes rich humus. Humus increases soil nutrients and organic matter in the soil.
  • Decreases root competition: You don’t want grass and other plants popping up at the base of your trees because they compete with the tree for water and nutrients (and often win!).
  • Protection from lawnmower damage: If you walk around any city or town and look closely at trees planted in grass you’ll notice that many of them have wounds low down on their trunks from being run into with lawnmowers and other equipment. A nice, wide mulch ring will ensure you never accidentally run into your tree causing damage.
  • Dang it looks good! Mulch rings lend a tidy and aesthetically pleasing appearance to your landscape.

How to put Mulch Around a Tree

We recommend using woodchips as mulch for your trees. Medium to coarse textured woodchips work best, as fine material (eg: finely shredded bark mulch) can pack down and inhibit water from reaching the roots. Avoid rubber mulches and rocks if possible.

Woodchips are available for free in many municipalities. If you’re having tree work done on your property you can request to have the woodchips dumped in your driveway.

If you have many trees to mulch and a big garden you could sign up for a service called Chip Drop. You submit your name to a database that tree care companies can search when looking for somewhere to get rid of a load of woodchips. Our dump trucks fill up several times a week and we’re always looking for places to deposit woodchips and clear out our trucks for the next job.

Once you have your load of woodchips and are ready to mulch there are a few tricks and tips to keep in mind for applying mulch around a tree.

Depth

Always mulch 2-4” deep, never greater than 4” deep. Mulch that is too deep can inhibit the oxygen exchange that needs to happen between roots and the atmosphere. In other words, roots breathe oxygen just like we do! Most of the roots of a tree are located in the top 6-24 inches of the soil, so make sure you’re not covering them up with too thick of a layer of mulch.

Size

The wider the mulch ring the better. We suggest 4-6’ or greater from the trunk of the tree. The farther out you can spread the mulch ring the better for the tree because the less the roots have to compete with grass for water and nutrients.

Roots stretch wider than the canopy, so give them room to breathe! It’s especially helpful to have a large mulch ring around young trees. The growing roots will thank you!

Make sure you leave the root flare (base of the tree) slightly exposed. Aim for flat round mulch rings, like a donut, and avoid “volcano mulching,” or piling mulch up against the trunk. More on that later.

how to put mulch around a tree

Edging

We suggest a natural edge. If you dig a 2-4” deep trench around the outside of the ring, the mulch will naturally fall into it. No need for plastic edging!

In fact, when roots hit the plastic edge they interpret it as a barrier, and begin growing in a circle. This can lead to girdling roots (pictured left).

say no to volcanoes!

While walking around your neighborhood or town you might notice the strange phenomenon of people creating tall piles of mulch around their trees, or what we like to call “volcanoes”.

This great illustration from Trees Louisville shows the difference between a mulch ring and a volcano.

Illustration courtesy of Trees Louisville here.

As you can see in the first illustration of proper mulching, the mulch is pulled away from the base of the trunk. You can build it up a bit higher around the perimeter in order to create a basin for the water to infiltrate the soil.

The picture on the right illustrates the shape of the volcano style of mulching, which is a big no-no! Mulch that is piled up against the trunk of the tree traps moisture against that area which can lead to rot and decay. It also provides a home for insects and rodents which will sometimes eat away at the bark.

When you’re mulching your trees keep the above images in mind – wide, flat rings like a donut, no volcanoes!

Investing some money for mulch and a few hours of labor each season can help your tree thrive for a lifetime. Did you make a beautiful mulch ring? Neighbors might find it strange to get excited over a mulch ring, but we get it! Email us a photo at [email protected]! Show off that beautiful donut. 

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