Since we have been discussing mulches it seems time to discuss the practice of pilling mulch up on the trunk of a tree that is commonly called “volcano mulching”. It is very harmful to the tree and this practice is illegal in many states! 

A tree has two types of bark on it. The first is the rough bark that is above ground. It is naturally resistant to fires, insects, and microbial degradation and is designed to protect the tree in a dry environment since it is above the ground. The other type of bark is on the roots and tends to be smoother, thinner, and built to survive in a moist environment (e.g. the soil). 

When one places a pile of mulch around the root flare and trunk of the tree, it creates a moist environment that the bark cannot withstand for a long period of time. The bark softens from the moisture and is attacked by all sorts of life from insects and disease to rodents that can now eat the bark. 

Corrupt or ignorant landscapers like to do this as trees slowly weaken from the stress over time. As the tree weakens it may develop disease or insect problems. The landscaper then can sell the customer a “treatment” for the problem as they now earn extra money. This may go on for a year or two and then the tree eventually dies. Now the landscaper can sell you a replacement tree and collect hundreds of additional dollars of your money. 

Hence when mulching always make sure the flare and truck of the tree ARE NOT covered with mulch (or soil). 

When choosing a landscaper always ask them to show you pictures of their work. If they have mulch piled around the trunk choose someone else to do your work. 

The picture below is from Howard Garrett showing a tree that has died from having its trunk covered. Notice how the bark has rotted away.