Compared with the rest of the landscape, trees are about as low-maintenance as you can get, which makes them easy to overlook. Sure, you remember to water and fertilize them with the rest of the lawn, but they really need more than that to thrive. A regular maintenance program will add vigor and help prevent future problems.

Done properly, applying mulch around landscape ornamentals can be one of the best things you do for them. Mulching mistakes, by contrast, can stress and even kill plants. So it’s critical to familiarize yourself with mulching basics, as well as what kind of soil you’re working with.

The cover up
Overmulching is the most common mulching mistake perpetuated by a “monkey-see, monkey-do” mentality. In short, we’ve seen so many examples of mulch piled up high on tree trunks that we associate it with the correct way to mulch. This could not be further from the truth.

In fact, this is such a common problem that the International Society of Arboriculture has come up with a term to describe this improper method of mulching: mulch volcanoes. Its campaign against this technique implores landscapers to “mulch wide – not deep.” This epidemic of incorrect mulching has elevated to code-red status, becoming one of the leading causes of death of trees and shrubs.
Mulching too deep or too close to trees and plants can lead to plant injury and death in a number of ways:

Root suffocation. Roots need to breathe. Without acceptable levels of oxygen, roots begin to decline and will eventually die.

Dehydration. If you pile on the mulch too thick, you prohibit the penetration of water and dehydrate roots. In the case where water actually does make it through the mulch and to the soil, you then risk preventing natural evaporation, which will result in perpetually soggy soil and will eventually lead to root rot.

Fungus. Piling mulch against a tree trunk is an open invitation for fungi. The moist conditions provide the perfect environment for their growth and reproduction. Once the tree bark begins to decay, the fungi can easily enter the tree.

Insects. Research suggests some insects can instinctively detect a stressed tree or plant and will attack it preferentially. So not only will your ornamentals decline from the mulch, they will be less able to fend off insect pests.