Fungi in Landscape Mulches—Are They a Problem?

Homeowners are often troubled by the presence of slime molds, stinkhorns, and mushrooms growing in their landscape mulches; but, they are not harmful to landscape plants, and no known health hazards are associated with them unless they are eaten. They can be discarded or ignored and they will quickly decompose. The fruiting bodies of the artillery fungus are barely visible (tiny cream or orange-brown cups approximately 1/10 of an inch in diameter), but they are the source of serious problems, many of which have resulted in insurance claims and lawsuits. They are phototropic and orient themselves toward bright surfaces, such as light-colored siding on homes and automobiles. They “shoot” their black, sticky spore masses, which can be windblown to the second story of a house. The masses stick to the side of buildings and automobiles, resembling small specks of tar. Once in place, the spore masses are very difficult to remove without damaging the surface to which they are attached. When removed, a stain remains. A few of the spots are barely noticeable, but, as they accumulate, they may become very unsightly. To date, there are no known controls for this fungus, but a research program studying possible solutions has been initiated. We ask that anyone who has information or experience with the artillery fungus contact us to exchange information. A brochure describing 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—has also been prepared to educate consumers.