Mulch: A Tree’s Best Friend

What Is Growing in My Landscape Mulch?

(PDF publication from the Department of Plant Pathology at PennState College of Agricultural Sciences)

Landscape mulches are used to protect soil, conserve moisture, moderate soil temperature, and limit weed growth, as well as beautify and unify landscape plantings. Most mulches are mixtures of shredded wood and bark residues from lumber and paper mills, arboricultural and land-clearing operations, and wooden pallet disposal or recycling facilities.

Like other organic matter, wood and bark decompose over time. The primary organisms involved with their decomposition are bacteria and fungi, which derive their energy for growth from the carbon-based compounds found in wood and bark. These compounds include cellulose, lignin, and simple sugars. Bacteria are microscopic organisms that are not visible in the mulch. Fungi also may be microscopic, but many develop visible reproductive structures.

The fungi involved in the decomposition of landscape mulches are natural components of the environment. Some fungi, such as the artillery fungus, are "recyclers" and break down woody tissue directly. Other fungi, such as slime molds, consume bacteria and other organisms living in the mulch. These fungi are not harmful to landscape plants and no known health hazards are associated with them unless they are eaten. They can be found April through October, usually following rainy weather.

This PDF publication from the Department of Plant Pathology at PennState College of Agricultural Sciences describes the four common types of fungi growing in landscape mulches in the eastern United States--mushrooms, slime molds, bird's nest fungus, and the artillery fungus.

Click on the link below to download a PDF version of the publication.

What is Growing in My Landscape Mulch?

From: PennState College of Agricultural Sciences