Its Mulching Season; What's going on in my mulch beds?
Mulch is actually wood or cellulose in a state of decomposition.
Cellulose is very difficult to decompose. A few insects and fungi and bacteria
are capable of completing the task efficiently. Available moisture, as well as,
freezing and thawing are mechanical devices that help breakdown mulch. Fungi
and slime mold are almost always present in shredded wood. Spores, seeds of
fungi, and other lower plants germinate in the moisture laden dark matrices of
the mulch. The fungi's hyphae, with thread like fibers, are evident throughout
the mulch. When two strains of some fungi meet they are able to reproduce. The
fruiting body or mushroom is formed. The fruiting body is like the apples of
the apple tree and the hyphae is like the tree - branches, roots, and leaves.
The fruiting bodies can appear overnight and last a day or so. The purpose of
the body is to produce enormous amounts of spores to increase the survival of
the species. When the temperature and moisture situations are optimal, fruiting
bodies are more common. That is why after new (foundation) plantings that are
mechanically watered, there are often many new areas of fungi.
Where fruiting bodies erupt from the mulch, gardeners think
there is a problem. Remember the fungi are necessary for the cellulose degradation
and spores and the hyphae are omnipresent. The classic mushroom can be found in
mulch. Sometimes there are groups of mushrooms, which are in a circular motif
called a "fairy ring". The fairy ring is supposed to have been caused
by gnomes dancing in a circle, however, it is just the relationship and growth
of hyphae growing outwardly from a common center.
Bird's nest fungus and artillery fungus are members of the cup
fungi. They are cup or saucer shaped, and some are even irregularly shaped
depressions. Their normal colors are white, yellow, orange, and red. Many of
the cup fungi are so small the fruiting bodies go unnoticed to the untrained
eye. The spores from the cup fungi are mainly dispersed when water droplets
from rain or mechanical watering hit them and cause them to explode upward and
outward. These fungi grow best in old mulch, hence yearly applications of fresh
mulch prevent eruptions of spores.
The artillery fungi's spores often stick to masonry walls, and
sidings of homes. They are very difficult or seemingly impossible to remove.
(There is a home remedy soap mix that does a good job if needed). Slime molds
have the most hideous and obvious fruiting bodies. These bodies when moist,
seemingly appear overnight, and look like dog vomitus. White, to gold, to pink,
these bodies may dot a mulched area. They look ugly but are not dangerous.
Spores from fungi are extremely minute and can be carried long
distances by wind, birds, or man. They are commonly found in greenhouses,
woods, gardens, or any place where moisture and organic material allow
1. There are ways of dealing with the fruiting bodies. Once they
appear, remove and dispose of them in the trash to reduce the amount of spores
dispersed in that area. The other way to deal with the fruiting body is to
interrupt the life cycle of the fungi. This is often difficult because the
hyphae are usually not seen and the fruiting bodies usually come out overnight.
One may lime the soil to sweeten it, possibly changing the pH necessary for
sexual reproduction. A liquid lime mix sprinkled on the top of the mulch will
suffice (Example: AGGRAND Lime Plus).
2. A dilute solution of sodium hypochlorite may be used to
sanitize the mulch. From past experience we have found a 50/50 mix of water and
common Clorox to be very effective. First remove visible fungi and loosen the
top layer of mulch with a rake, then use a sprinkling can to wet the mulch
being careful not to wet the plants themselves. Repeat in 3 days if necessary.
3. The mulch may be loosened and flipped on a regular basis
during the rain season to help keep down the amount of available moisture for
vegetative and reproduction growth. Adding chemicals to the mulch may hinder
one's plants as well as the fungi - SO BEWARE! The available moisture lost to
the fungi is also lost to the root system of the plant. The safest method of
response is physical removal of the fruiting bodies to remove spore density.
4. If you experience spore spots from "artillery
fungus" try washing them off with a mixture of 3 tablespoons of Cascade
dishwasher detergent and 1 tablespoon Tide laundry detergent dissolved in 1
gallon of warm water. Scrub area with a bristle brush and rinse with clean
The fungi and their fruits are just part of nature's recycling
system. Since decomposition of cellulose is achieved in part through fungal
degradation, then it follows - where there is mulch, there is fungus. Do no
despair, the gardener and fungi can live in harmony. Man is part of nature and
must learn to understand and utilize it. The decomposition of wood improves
plant species and the gardener need only experience a few unsightly masses on
For more information regarding mulch and fungi, please contact
the Penn State Horticultural Department at (610)