Purdue University
Consumer Horticulture

Volcanoes in Indiana!

By Mary Welch-Keesey
Purdue University Consumer Horticulture Specialist


In their enthusiasm for neatness and uniformity, many gardeners have started placing a ring of mulch around tree trunks. There is nothing wrong with this. By keeping grass from growing near the trunk, you also eliminate the need to mow or use a weed-eater near the trunk. Both of these tools can damage the tree's bark, creating a potential entry site for diseases and insects.

Unfortunately, many gardeners, and professional landscapers as well, put the mulch right up against the trunk. And not just 2 inches deep but 4 or 6 or 8 inches deep. This phenomena has become so wide-spread that it has its own name - the volcano or "Mt. Vesuvius" syndrome. No, the tree won't erupt, but the bark covered by the mulch will stay continuously moist. Eventually decay will set in, followed by insects and wood rot. Plant death is inevitable.

You can rescue your trees and shrubs from Mt. Vesuvius syndrome by:

- Pulling the mulch 3-6 inches away from the trunk or trunks.
- Thinning the mulch so it is no more than 4 inches deep.
- Loosening the mulch periodically to improve air and water penetration.

An example of what NOT to do:

Correct mulching:

Site last updated: 24 March 2006

Questions about this article should be sent to Mary Welch-Keesey at mwelch@indyzoo.com.

Questions about this site should be sent to homehort@purdue.edu

The URL for this page is http://www.hort.purdue.edu/ext/WRG_volcano.html