How To Eliminate And Kill Mushrooms Growing In A Lawn
It's raining mushrooms! Okay, you're here because you or someone you know has mushrooms suddenly popping up in spots or all over the lawn.

What causes mushrooms to grow in my lawn?
If mushrooms are popping up in spots or all over your lawn it's either been raining a lot, you're watering too much, or the soil is not draining properly. Lawn mushrooms are a fungus which thrive in moist conditions and feed on decaying matter. They also like shady environments however this isn't always true. Dog, cat or other animal poop and grass clippings are two common sources of decaying matter that mushrooms feed on.

Will mushrooms damage my lawn?
Good news and bad news. Though they are unsightly, the good news is, with the exception of 'fairy rings', most types of mushrooms will not damage your lawn grass. Instead, they will actually help to break down organic matter in the lawn, which adds nutrients to the soil. Bad news is the presence of mushrooms indicates a moist to wet environment, and constantly soggy soil can lead to serious turf diseases, which can and often will damage your lawn.

If mushrooms are present due to a temporary period of heavy rainfall, during which the soil has become oversaturated and not had the time to dry out, then you probably won't see any long term damage to your lawn. When rainfall amounts return to normal the mushrooms should go away.

Fairy Ring Mushrooms
A little about fairy rings. Fairy ring (pictured above), a fungal infection that affects every type of turfgrass, results in the development of a visible full or partial ring in the grass. The ring is composed of mushrooms, darkened grass or both. Because the disease can be managed but is difficult to eradicate, gardeners should become familiar with ways to suppress it as a means of killing the mushrooms. Unfortunately, eradication of fairy rings is difficult if not impossible. Destruction of the fruiting bodies does not stop the fungus from spreading (sort of like pulling oranges off your tree does not stop the tree from growing). Although it is possible to dig up and replace the soil in which fairy rings grow, the rings will reappear if their food source has not been removed. Fairy rings will disappear naturally once their food source is depleted.

How to control common mushrooms and fairy rings in the lawn 
You can treat your lawn with a fungicide however, if you don't correct contributing causes, chances are the mushrooms will just come back.

  • Since mushrooms feed on decaying matter, collect grass clippings when mowing during rainy periods. Or, if you don't have a grass catcher on your mower, rake up clippings after mowing.

  • Mow grass regularly to a height of 2 to 4 inches, depending on the grass species. Allow grass to grow long enough so that you will mow no more than one-third of the grass' new length.

  • Poor fertility and low nitrogen levels encourage fairy ring mushroom growth. Apply a nitrogen fertilizer.

  • If you have an automated irrigation system, reduce moisture in the soil by cutting back on the amount of time the system runs. Turn the sprinkler system off during periods of heavy rainfall and don't resume irrigation until absolutely necessary. Irrigate the lawn before 10 a.m..

  • Aeration and/or dethatching can help to improve soil drainage which, in turn, will eliminate the environment mushrooms require in order to thrive.

  • At first sight, remove any mushrooms that appear in the lawn. Doing so will help to prevent their spores from spreading.

  • Mushrooms prefer a shady to partially shaded environment. Targeted pruning to thin trees, or removal of low hanging limbs, can allow more sunlight to reach the lawn. Major pruning should be performed while the tree is dormant, during winter. If you doubt your pruning skills, and are afraid you'll damage or kill your trees, contact your local arborist to do the pruning.

  • Remove pet or other animal poop as soon as possible. If you've ever been in a cow pasture during a rainy and wet summer you might have noticed all the mushrooms growing in what we used to call the "cow plops."

  • Last but not least, check your lawn to identify any low-lying areas or depressions where water stands for too long after a heavy rain or irrigation. Then take steps to fix or improve drainage in these areas. Small depressions no more than a foot wide can be smoothed over by topdressing with sand or very sandy native topsoil. Larger depressions can be fixed by removing the sod and applying native screened topsoil to fill the depression. After filling the depression, set the sod back in place and tamp and water as necessary until it has rooted well. If there are many depressions throughout the lawn area you might want to consider renting a sod cutter to get the job done. Digging sod with a shovel is back breaking work!