Volcanoes in Indiana!
Mary Welch-Keesey, Consumer Horticulture Specialist

Volcano mulched tree (larger picture)

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 continually moist. Eventually decay will set in, followed by insects and wood rot. Plant death is inevitable.

Correctly mulched tree (larger picture)

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.
  

Story Resources

Planting Landscape Trees and Shrubs (PDF 968K)

Pruning Ornamental Trees and Shrubs (PDF)