After you have given your lawn a good soaking, or a downpour was followed a number of warm days, you may see white or speckled mushrooms appear on your lawn. Mushrooms thrive in damp conditions, and the fungi they come from are present in mulch and humus, as well as in the soil under your lawn.
Long before you see mushrooms appear on your lawn, spores start to grow in decomposing organic matter. This matter may be dead leaves or trees or be found in the soil. As the spores grow, long strands called hyphae appear. Too tiny to see with the naked eye, hyphae from a number of spores then join together. The union of hyphae creates mycellium, which in turn produces its fruit, a mushroom. Mushrooms release spores into the air, and the whole process starts all over again.
Can Mushrooms Harm My Lawn?
Most mushrooms do not harm your lawn at all. They help to release nutrients into the soil as they feed on decomposing material. However, gardeners and homeowners dislike seeing them pop up in the green expanse of their grass. Keep in mind that many mushroom varieties are poisonous to both humans and pets. Never cook or eat mushrooms that grow in your yard. Remove them as soon as they appear, and wash your hands well with soap and water afterward.
There is a type of fungi that can harm your lawn. Called fairy rings, this fungus is first seen as a circle of a different green or taller grass. The so-called fairy ring can be a foot or more in diameter and sometimes is ringed with mushrooms as well. If you notice fairy rings soon enough, you can get rid of them by aerating the soil to retard fungus growth. Patches of lawn that have already started to die need to be removed and replaced.
Discouraging Mushroom Growth
Pick and discard mushrooms as soon as you see them. Getting rid of the mushrooms that appear in your lawn will prevent them from spreading their spores. You will most often see mushrooms after a heavy rain or in damper areas of your lawn. Of course, the lawn will constantly be exposed to spores brought in from the wind, as well as existing mycellium from decaying organic matter. At best, you can take steps to discourage further mushroom growth. If you have pets, remove their excrement from the lawn. Rotting mulch and old tree stumps harbor mycellium, so you may want to get rid of them.
Since mushrooms thrive in damp, poorly drained areas, water less frequently to allow the soil to dry out. Use an aerating tool in your lawn to promote better water absorption and drainage. Although mushrooms are how fungi reproduce, spraying fungicides on them will not solve your problem. Fungi will continue to exist under the lawn surface. That fungi will only disappear when it no longer has a food source. Feeding your lawn with a nitrogen-rich fertilizer will help speed decomposition, discouraging the mycellium from producing mushrooms.