Mulch

The malpractice of piling mulch high on tree stems to approximate the look of a volcano is well underway in Ohio. This horticultural horror, commonly known as a “mulch volcano” or “volcano mulch,” produces a range of detrimental effects, including reshaping tree root systems and interfering with water infiltration and retention.

On a recent walk through a cemetery I frequent, I noticed several tree bases that were treated with a herbicide. In the past, the previous cemetery manager told me he never used herbicides and would have his workers string trim around all the grave markers and trees. So why the change?

When done right, organic mulch, particularly hardwood bark mulch, will provide a wide range of benefits to trees and other woody ornamentals. When done wrong, it can produce a range of detrimental effects that wreak havoc on tree health from vascular strangulation to moisture starvation.

The vast majority of the trees and shrubs used in Ohio landscapes evolved in ecosystems with soils topped by an organic layer. Think forest and grassland soils. Aged hardwood bark mulch serves as a stand-in for leaf litter found beneath trees in forests. However, if a little is good, more is not better.

Organic mulch can provide wonderful benefits to landscape trees and shrubs as well as enhancing landscape aesthetics. Or it can slyly take the form of a horticultural horror cunningly robbing woody ornamentals of their vigor.

Mulch piled around tree trunks to stratospheric heights has been called many things (some not printable) such as pyramid mulch and mountain mulch. My personal favorites are mulch volcanoes (or volcano mulch) for stratovolcano-like creations and mulch mounds for those that resemble shield volcanoes.

Sometimes we run across bizarre things in Ohio landscapes that simply defy explanation. Such was the case yesterday when I came across "tree moats" (sometimes called "mulch moats") in a park near my home in the southwest part of the state. I've encountered this bizarre practice before and fail to fathom the logic behind this ludicrous practice.