Mulching Trees Properly

Bruce County, Grey County, we need to talk about Volcano Mulching. I also call them mulch-canoes, but when I write that it looks more like a boat made out of wood chips than the practice of burying a tree’s trunk under a pile of organic matter. 

You don’t have to go very far before you can see the trend of volcano mulching that is happening in our area. Farmers are doing it. Town dwellers are doing it. Even municipal workers and landscapers are! 

The urge to pile mulch around the base of a tree comes (I’m sure) from an honest desire to help the tree. People must feel that they are simulating a forest floor with leaf-litter and humus. But it isn’t helping. It is only working to create more problems. 

Mulching around trees is good. Mulch has many benefits from adding nutrients to the soil as it breaks down, to subduing grass and other plants that compete with the tree for water, and helping to retain moisture that the tree needs.

However! A small circle of mulch stacked in a cone-shaped pile around the base of the tree is providing little of the benefits I mentioned above. In reality, the added material captures moisture and keeps it against the trunk bark. 

Trees like to have their root-flares exposed. Let’s have a look at some big beautiful root flares of trees I’ve seen in the area:

Here is Sugar Maple (Acer saccharum) from Tara showing off a beefy root flare.

This beautiful old tree has it root flare exposed.

Here is a Norway Spruce (Picea abies) from Thornbury with a dramatic root flare, and even a surface root. 

This fallen needles of this spruce act as mulch, in much the same way as forest floor.

I could go on, but you get the idea. 

Sandy Feather at the PennState Extension writes: “When wet, the mulch holds too much moisture against the bark, which can cause it to start to break down. And as the mulch starts to compost, it heats up, which can further damage the bark and the underlying vascular tissues, compromising the tree’s ability to transport water and nutrients.” (source)

If trees are to benefit from a nice layer of mulch, it needs to be done in a way that keeps the root flare exposed. Mulch helps the tree when it is under the drip-line, improving the soil with organic material and helping to retain water. 

One reason mulch piles under trees are so common is because landscapers use it to avoid damaging trees with string trimmers. As an alternative, try removing grass and exposing the soil.

A paper birch (Betula papyrifera) with the grass around its trunk having been carefully excavated to reveal its surface roots and trunk flare.
This birch tree has had the grass carefully removed from around its base to expose its root flare.

Once the grass has been removed, a shallow layer of un-dyed, well composted mulch could be added in between the exposed surface roots.

There are plenty of ways to care for trees, mulching is one. Volcano mulching is not. Let your tree show off its root flare. Mulch with care!

If you have any questions about mulching or any other aspect of caring for your trees, please contact Biemann Tree Care by email or phone through the contact page on this website.  

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