Why Do Mushrooms Pop Up in the Yard?

Mushrooms in the lawn indicate the presence of a fungal colony in the soil underneath your lawn.

Mushrooms, or toadstools, along with inky caps, puffballs, stinkhorns and bird's nests are the fruiting bodies of fungi. Fruiting bodies grow and release the spores, allowing the fungi to reproduce. When the spores land on a surface conducive to fungal growth, a new colony grows. Fungal spores are pervasive, found in nearly every outdoor and indoor environment, so mushrooms often appear in places we wouldn't immediately expect them to, such as lawns.

Mushrooms and Lawns

Fungi are important parts of an ecosystem; by breaking down dead and decaying organic matter, they help release nutrients from the organic matter into the soil, thereby imparting the nutrients into plants and other organisms. Therefore the presence of mushrooms in your yard should not be considered an indication of poor lawn health. Microscopic threads underground, called mycelium, band together to form mats and to eventually form a fungal colony. Mycelium threads need plenty of moisture to grow, so you are much more likely to find mushrooms in your lawn after rainfall, when the mycelium in your soil has been provided with enough moisture to mat together and form a fruiting body in the form of a mushroom.

Why My Lawn?

Since fungi do not contain chlorophyll, the chemical plants use to obtain energy from sunlight via photosynthesis, their need to derive their energy by consuming dead organic material, an abundance of which is found in the lawn since dead insects, leaf debris, grass clippings and the like are more likely to collect on the ground. Lawns also collect large amounts of moisture from rainfall, providing underground mycelium with abundant supplies of the moisture and nutrients that they need to grow and produce fruiting bodies in the form of mushrooms.

Types of Mushrooms

Probably the strangest of mushroom formations that can appear in your yard are called fairy rings, characterized by enormous (sometimes over 12 feet across) circles of mushrooms with alternating patches of dead and healthy grass. Other mushrooms that you are likely to find in your yard include inky caps (mushrooms with caps that decompose into a black, inky liquid), stinkhorns (quite literally, mushrooms that smell terrible and resemble horns), puffballs (giant ball-shaped fruiting bodies that burst to spread spores) and bird's nests (fruiting bodies shaped like a small nest with several spore-filled, egg-shaped growths in the center of the nest).

Removal

Despite the overall beneficial nature of mushrooms in the lawn, it is important that some mushrooms are toxic to humans. Other mushrooms can sometimes harm your lawn grass. In addition to these reasons, some homeowners choose to remove mushrooms simply for cosmetic reasons. You can remove lawn mushrooms by raking or sweeping them or pulling up by hand (wear gloves and wash your hands afterward). Note, however, that removing the mushroom will not remove the mycelium mats underneath your lawn, and that fungal spores can easily be wind blown onto your lawn from other areas, so the chances are good that you will continue to see new mushrooms growing in your yard even after you remove the existing ones.

References

• University of California Agriculture and Natural Resources Statewide Integrated Pest Management Program; Mushrooms and Other Nuisance Fungi in Lawns;
• Washington State University Extension; Mushrooms in Yards; Steve Whitcher
• Auburn University Ask Aubie; What Makes the Mushrooms Grown in Our Yard After it Rains?; Dave Han