Q. I am noticing a lot of weird mushrooms growing in my mulch this season. Are they harmful to my plants?
A. According to extension specialists at the University of Arkansas, wood made from hardwoods provides a perfect environment to grow all types of mushrooms, especially when we receive abundant rainfall as we have this season. Mulch derived from the bark of softwood trees such as pine and cypress tend to be more resistant.
Many folks are alarmed at the appearance at some of the strange fungi that appear in mulch. Bird's nest fungi, artillery fungi, slime molds and stinkhorn fungi often appear on decomposing wood mulch in the landscape. These fungi live only on decaying plant matter, so they do not harm living plants.
Bird's nest fungi and artillery fungi can be a particular nuisance since they can forcibly eject their sticky spores onto home vinyl siding and automobiles nearby. They can be difficult to remove and can damage the surfaces they adhere to. Recent research from Penn State University has shown that adding mushroom compost to wood mulch can reduce or eliminate artillery fungus.
Slime molds are a group of primitive fungi that can also appear on moist decaying mulch where they feed on bacteria. The dog vomit slime mold, or scrambled egg slime mold is perhaps the most common. Spores of the slime molds can remain viable for several years. As the body of the slime mold matures, it changes from a wet, slimy consistency to a crusty mass that looks like dog vomit. To say it is unappealing is an understatement.
Stinkhorn fungus has a characteristic long and tapered stalk. It is pinkish orange in color with a dark green to brown slime material at the top of the stalk. Stinkhorn has an unpleasant and offensive smell that has been compared to that of rotting meat. Stinkhorn can also be a nuisance as it attracts.
When mushrooms appear in mulch, simply remove the fungi with a small spade or shovel, place in a bag and send it off to the landfill. One can wear a cloth mask (the kind that many doctor's offices now have to help prevent folks from spreading colds and flu) to avoid inhaling the spores of the fungus. Some folks are sensitive to molds, and that are what these fungi are.
After removal, stir and fluff up the much – this will help change the environment and reduce the chance of more mulch appearing.
Some folks give up and replace the bark mulch with stone or other materials. These materials don't work as well to reduce soil temperatures and conserve moisture, and eventually weed control becomes impossible without the use of herbicides.
Replacing the mulch yearly can help. The longer a bark mulch is used, the greater the chance of weird mushrooms.
Spraying fungicides or disinfectants on the mushrooms is not recommended.
For more, you go to this link from Penn State University for neat pics and info: https://extension.psu.edu/what-is-growing-in-my-landscape-mulch-mushrooms-slime-molds-and-fungus.
The Plant Medic, written by Ricky Kemery, appears every other Saturday. Kemery retired as the extension educator for horticulture at the Allen County branch of the Purdue Extension Service.