Now that winter has removed the blossoms and leaves from our landscapes, mistakes are all the more obvious and seem to shout out from everywhere. None is worse than incomprehensible activity pursued by some people referred to by state agricultural extension service representatives and master gardeners pejoratively as “volcano mulching.”

"Volcano mulching" is the practice of mounding huge amounts of mulch up around the base of a tree. No one is quite sure how this practice got started. Some sources speculate it was started by someone too lazy to dig a hole to plant the tree. Or maybe despite regular articles across the country by all manner of writers, people are still uneducated about volcano mulching and someone somewhere thought it looked attractive. Perhaps they were thinking if some is good, more is even better. I think there also could be a financial motive at work. More mulch means more money to charge if you are “professional” landscaper. 

No matter what the motive, it is just wrong. First of all, it looks bizarre, but more important it ends up being highly damaging to the life of the tree. Perhaps there is another financial motive here. In that if eventually the tree dies the “mulchee” can charge to remove and replace it with another and start the process all over again.

Too much mulch too close to the tree’s trunk allows rodents to burrow and covertly chew the bark, particularly during the winter and early spring when other food sources are limited. Particularly with a young tree, the moisture retained close to the bark in the mulch softens the bark and also creates the perfect environment for termites, fungal diseases and cankers to breed and attack the tree. 

Certain tree varieties roots also will migrate up into the mulch and cause either death from frost damage or water loss during a drought. It also can lead to tree instability.  Some people do not realize roots need oxygen to survive as well as water.  Too much mulch restricts oxygen flow.

Oddly sometimes too much mulch can have exactly the opposite result of what is intended. Rather than helping retain moisture in the correct application, it keeps the soil too dry because the top of the mulch hardens or becomes so overpopulated with fungus that water just runs off.

The correct amount of mulch is just two to four inches spread around the base of the tree away from the trunk in more of a donut shape than sloping side shape.  There should be no more than an inch close to the trunk. A tree trunk naturally flares slightly as it meets the proper soil/mulch depth. One should be able to see this. Ideally there should be mulch or shredded leaves and no grass around the entire drip line of the tree but if people where to stop over mulching that really would be enough to ask for as a New Year’s resolution in 2011.

One concerned arborist reportedly has become so alarmed by volcano mulching that she keeps pre-made posters in her car. When she notices an instance she hits the brakes, jumps from her car and attaches a sign to maligned trees to call attention to them and their silent suffering.