On June 26, 2020, we published a blog article on tree ring mulching. This article gave the pros and cons of mulching around individual trees and how to do it correctly. As I have seen multiple times and which is explained in that article the common, but false practice of creating mulch volcanoes. A couple of other bad practices that I will discuss in this article is #1 use of edging and #2 use of non-organic mulches.
The use of edging whether it is steel, plastic, aluminum or block is very common. People want to keep their rings nicely shaped and believe the use of a physical edging is the best way. This practice is fine for the early life of a tree, but as the tree matures it should be understood that these edgings should be removed. Tree roots grow and the flare of the tree expands heaving edging to be unsightly. Heaving plastic/metal edging is a common problem here in Michigan because of the freeze/frost cycle, then add the growth of the tree and this problem only compounds. Block walls need a crushed stone base of 6-18” depending on various factors. This base may be fine when it is installed outside the root ball when the tree is fairly new, but as the roots expand they will grow through this stone base and heave the wall up. This is especially the case with shallow rooted trees such as Maples and Elms. Trying to install this type of edging should be avoided at all cost as a tree has matured. Damaging roots by digging and cutting will only have the outcome of a sick or dead tree.
Also, installing edging around evergreen trees is just a waste of money. Evergreen trees will grow a foot of more of width per year. If you install edging a few feet away from the drip line of a 8 foot Norway Spruce, within 3 years that edging is buried under the tree. Having a natural edge (spade or machine cut) allows you to expand that bed as the tree(s) mature.
Another bad practice is the use of weed barrier and/or non-organic mulches….aka decorative stone. Once again as the tree matures it moves the ground causing an unsightly appearance. Plus in general decorative stone is not the best mulch for plant health. A nice 2-4” depth of natural, wood-based mulch (shredded bark, wood chips, colored mulch, etc) is always the best practice. Plus with wood-based mulch needles of evergreens can fall and decompose with the mulch. In a stone based bed, the needles can easily get lost in the rocks making it nearly impossible to remove.
Please consider these best practices when creating an outstanding landscape.