Tree Mulching Tips from Arlington Parks and Recreation
By Danica Dodson, Arlington Parks & Recreation
Posted on October 08, 2020, October 08, 2020

Mulching a Tree

Mulching your trees seems pretty self-explanatory, but did you know there’s actually a technique to mulching properly? The amount of mulch and frequency of adding mulch are crucial factors in maintaining the health and appearance of your landscape. APRD’s Urban Forestry Land Manager, Wendy Pappas, suggests these tips for tree mulching so you can get the most out of your trees and allow them to thrive.

Purpose of Mulching

You may be asking, “Do I really need to mulch my trees?” There are many practical benefits to adding mulch to your trees, aside from improving the appearance of your landscape and giving it a more finished look. If done properly, mulch will add organic matter and vital nutrients into the soil as it decomposes, which does wonders for the health of trees. Mulch also creates a visual barrier for mowers and weed trimmers so the tree will not get hit or scraped during landscape maintenance. Additionally, mulching helps to suppress weeds that pop up around the base of your trees.

Don’t Overdo Mulch

When it comes to mulching your trees, more isn’t always better. Trees need oxygen at their roots to survive, which means piling excessive mulch at the base of a tree can prevent the tree’s roots from receiving enough oxygen. This mistake can cause the tree to suffer or even die.

Another common mistake that should be avoided is covering the tree’s bark with mulch. Covering the bark can cause rotting, fungus, mold, and various other problems that could lead to the death of the tree. Piling up a tall mound of mulch at the base of a tree is called “volcano mulching”, which is extremely bad for trees.

The Correct Technique

The first step to properly mulching your tree is to determine the area of the tree’s root flare. The root flare is the flared part of the tree trunk at the bottom of the tree. It can be difficult to determine exactly where this part is on some trees. If this is the case, simply dig around a bit at the base of the tree until you can spot it.

Remove any grass from the root flare and tree trunk area. When you begin to add mulch, make sure to leave a few inches between the trunk and the mulch to prevent moisture and fungus from building up on the trunk. Continue to add mulch around the tree, and make sure your mulch does not exceed 3 inches in depth. You can mulch all the way out to the drip line (the area located directly under the outer circumference of the tree branches) if you are mulching a small tree. This will create a barrier so mowers will not run over the root flare or scrape the tree bark.

Frequency of Mulching

Once the initial mulching is complete, trees do not need to be mulched very often. A good rule of thumb is to mulch trees when the mulch looks thin or you can see the soil. You might only need to re-mulch your trees every few years, and you’ll want to avoid piling new mulch on top of old mulch. If your trees have plenty of mulch around them but the mulch begins to look dull and flat, simply grab a rake and give the mulch a good fluffing to bring it back to life and freshen up the appearance. After a while, the mulch will eventually begin to decompose and add organic matter into the tree’s soil.

We hope these tips help you become a mulching master! Check back later for more fall gardening tips from Arlington Parks and Recreation’s Forestry and Beautification team.

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