They might show up after a rainy spell or emerge in new sod. Or you might have a fairy ring surface in your yard. Whatever the situation, having mushrooms pop up in your lawn can be a nuisance, an eyesore and, if you have children, potentially dangerous. Learn why mushrooms appear and what you can do about them.
What are mushrooms?
Mushrooms are actually part of a fungus that grows underground, hidden from sight. The mushroom is the tip of a fungus iceberg, if you will – a clue that a large fungus lies buried in soil. Lawn fungi and their mushrooms don't harm a lawn. They're actually good guys in the ecosystem of your yard, breaking down organic material into nutrients your lawn can use.
A mushroom reproduces through spores, similar to seeds. The mushroom releases the spores, which spread by wind or water, to start a new fungal colony.
When most people hear the word "mushroom," they think of the typical umbrella-shaped one, which is sometimes called a toadstool. But you might also spot other types of lawn fungus, including puffball, shaggy mane, Japanese parasol or the oddly-shaped and smelly stinkhorn.
When Mushrooms Occur
When mushrooms appear on the lawn, break them off or mow over them. If you have pets or children who might be tempted to taste mushrooms, gather the broken pieces and dispose of them.
Cause: Buried Organic Matter
A fungus grows by breaking down organic matter. In a lawn, that organic material could be buried timber, a stump, or tree or shrub roots that remain underground after plants have been removed.
Solution: In most cases, when the fungus has finished breaking down the buried organic matter, the fungus (and accompanying mushrooms) will disappear.
Sometimes you can hasten the material's breakdown by applying nitrogen fertilizer. Use a readily available nitrogen source, not a slow-release one. Aim for a rate of 1/2 to 3/4 pound of actual nitrogen per 1,000 square feet of lawn. If you don't mind disturbing your lawn, you can also try digging up the organic material.
Cause: High Moisture
Periods of prolonged rain can coax mushrooms to form, as can overwatering a lawn. Heavily compacted soil and a thick thatch layer can create drainage problems, which provide ideal growing conditions for mushrooms.
Solution: While you can't do much about overabundant rainfall, you can address lawn watering practices. Aim for deep, infrequent lawn watering, which encourages turf to develop an extensive root system. Learn tips for lawn irrigation. For drainage issues caused by compacted soil, try aerating your lawn. A thick layer of thatch in your lawn also could contribute to drainage issues.
Cause: Low light
While not all lawn mushrooms thrive in shady conditions, many do. If a corner of your yard offers high soil moisture combined with low light, mushrooms may appear.
Solution: Address the moisture issue using one of the techniques listed above. Next, if trees shade the lawn, tackle light tree trimming to allow more light to reach grass.