During the summer in Maryland, many anxious gardeners are discovering examples of fungi growing in their lawns and gardens and then bringing them to me for diagnosis. Gardeners are concerned that these very noticeable and often bizarre-looking growths might be doing some sort of damage to their garden plants. They almost always make the right assumption - that these things are fungi. But they want to know: "What kind ARE they and what are they doing in my mulch, lawn or my tree’s bark?"
These fungi are saprophytes, which feed off of decaying organic plant material, such as bark mulch, tree bark or bits of decaying roots or twigs buried in the grass. They do not attack live plants directly, except for the mature bark of growing trees (which are, in fact, non-living). The most common examples familiar to most of you are mushrooms and toadstools. But others found in the landscape from time to time are less familiar to you. Slime molds, which are not technically fungi, often cause the most concern.
One such slime mold is Fuligo septico, often called by a rather disgusting common name “dog vomit fungus”. It appears usually on bark mulches in beds after a wet spring or during the hot, humid summer. The common name aptly describes it to a T. It is a whitish, frothy mess, often mixed with a wet yellow or orange layer on top. But again, they are not harmful to your plants, just feeding on the decaying mulch. Another familiar saprophyte is commonly called “stink horn”. The fruiting body of this fungus is a crescent-shaped stem which looks like a cow’s horn that comes to a pointed tip. The color of the horn is often red, yellow or orange. When the horn decomposes, it gives off an offensive order, hence the “stinking” part of the name. You may also see fibrous bracket fungi, whose fruiting bodies appear on the bark of mature trees and look like steps. They come in various colors, most common are off-white, tan and brown, but may also be found is bright orange and yellow. They feed off the tree bark on which they are attached and they aid in the decaying process, which causesminor blemishes to the tree’s wood. You will find the bracket fungi called “conks” by most, probably because of their seashell-like appearance. They can be found in various sizes, and some may grow as large as several feet in diameter.
What you see in all of these examples of saprophytic non-green plants are the fruiting bodies, which is the structure that is indispensable to reproduction, which is to produce spores. Mushrooms, toadstools and puff balls have familiar-looking fruiting bodies, which when “ripe” will broadcast millions of microscopic spores into the air. Although these saprophytic plants are normally no direct threat to your garden plants, many do produce strong toxins that make them among the most poisonous of plants.
My last bit of information on this subject is that there are NO controls that you can use on them, to except remove them from your garden with a rake and shovel and put them in the trash. Fungicides that control parasitic fungi on green plants WILL NOT kill or prevent saprophytic fungi in the garden.