What Causes Mushrooms in My Yard? (2024)

Mushrooms are great in dishes like chicken marsala and risotto, but they’re much less appetizing when they sprout from the lawn you’ve spent so much time, effort, and money cultivating. But what causes mushrooms in your yard?Decaying organic matter, wet conditions, fertile soil, excess thatch, and poor drainage are the main causes.

Why do mushrooms grow on lawns?

Before we get into prime mushroom growing conditions, let’s discuss the science behind their development.

Unlike plants that sprout from seeds and need sunlight and warmth, mushrooms grow from fungal spores that thrive in damp, dark conditions. Most of the time, the fungi live in the soil or the grass, breaking down organic matter to create nutrient-rich soil that drives fantastic grass growth.

When the conditions are right, the fungi start “fruiting” and send up what we recognize as mushrooms when they pop up in the grass. Under suitable conditions, fungi send up fruiting bodies quickly; mushrooms appear within a day or two in the best conditions.

As they mature and start closing in on the end of their life cycle, they drop spores that disperse in the air, landing throughout your yard. These spores lay dormant in the soil or grass until conditions are right when they begin proliferating and repeat the cycle.

Optimal conditions for mushroom growth

Decaying organic matter

Mushrooms often grow where decaying debris like tree trunks, branches, or compost releases significant nutrients into the soil. They are heterotrophic organisms that get nutrients and energy from other plants or organic materials.

Fungi produce enzymes called ligninases that help decompose woody materials containing lignin, an organic polymer that is a primary support constituent in wood.

Hence, mushrooms often grow on fallen trees in forests and other areas with hard-to-decompose organic matter.

Cool, shady, damp conditions

Fungi are highly influenced by moisture and cool temperatures. Therefore, you’ll frequently see mushrooms growing in shady areas like under trees and shrubs, or during cool, rainy periods, you’ll see them anywhere on your lawn.

According to the American Mushroom Institute, the ideal conditions for mushroom growth are about 70 degrees Fahrenheit with more than 90% humidity.

Poor drainage

Mushrooms also grow in compacted soils because of their poor drainage. A lack of air circulation and high water retention in the soil make the fungus active.

Excess thatch

When excess thatch — the layer of living and dead shoots, roots, and stems accumulating on the soil surface — builds up, you’ll see mushroom growth. The fungus feeds on decaying organic matter in the thatch and thrives in the humid conditions created by poor air circulation through the thatch layer.

Fertile soil

Mushrooms cannot grow in soils lacking nutrients, so if your lawn is fertile, you will likely see mushrooms on it. While they may be an eyesore, they signify excellent soil fertility.

Newly returfed lawns

Your newly laid sod may have mushrooms because the harvesting and transportation of turf can lead to the sporing and growing of new mushrooms.

What are the different kinds of lawn mushrooms?

Mushrooms come from many different types of fungi present in the lawn and soil. They come in a wide variety of shapes, sizes, and colors based on the parent fungi and growing conditions.

Mushrooms develop into iconic shapes with an elongated stem, topped off with a cap to facilitate spore dispersal. For some, the spores are formed in the gills under the cap. Since they sit up off the ground, it makes it easier for the spores to disperse in the air when they drop from the cap. Other types of mushrooms form their spores within enclosed structures that forcibly open and “puff” spores into the air.

Some mushrooms are brightly colored to warn predators of their potential harm if eaten. However, colors are also related to the type of fungi and growing conditions such as humidity, temperature, and sunlight.

The most common lawn mushrooms are:

• Puffballs (Lycoperdon spp.): round and white, with no visible gills and spongy flesh
• Inky caps (Coprinus spp.): vary in color but are distinguished by the black inky goo that drips from the edge of the cap
• Lawn mower’s (Panaeolina foenisecii): one of the most common lawn mushrooms, greyish or brownish at first, darkening as they mature
• Milky conecap (Conocybe apala): milky white when young, turning a pale beige with a thin, smooth cap that often splits at the edges
• Birds nest (Nidulariaceae spp.): look like a brown, grey, or white “nest” with small brown or white “eggs” inside
• Stinkhorns (Phallus spp.): distinct phallic shape and putrid odor
• Meadow mushroom (Agaricus spp.): starts out white with light pink gills that darken to blackish brown
• Death cap (Amanita phalloides): usually larger with white gills that do not attach to the stalk, may have a yellow or green tint on the cap
• Yellow fieldcap (Bolbitius titubans): start out bright yellow, quickly fading in color as the caps flatten out
• Ivory funnel (cl*tocybe dealbata): ivory-colored, powdery caps and delicate funnel shape
• Death angel (Amanita verna): pearly white stem with swollen base and white spores
• Flowery blewit (cl*tocybe irina): pale beige turning to pinkish brown, grows low to ground
• Fairy ring (Marasmius oreades): tan to reddish brown with off-white gills, grows in a ring

Fortunately, most of the mushrooms that grow on lawns are nonpoisonous, but it’s important to take a close look at them and identify them if you have kids or pets that could taste them. Look carefully at their height, diameter, and stem and cap color, and notice any distinct markings. Then, try to identify them by comparing what you have to online photos.

Do mushrooms in your lawn have any benefits?

Not only do mushrooms show that you have healthy, productive soil, but they also have several benefits for your lawn.

• When mushrooms pop up, they indicate the presence of beneficial fungi responsible for breaking down organic matter and releasing nutrients into the soil. These nutrients boost the soil fertility, providing nutrition for your lawn.
• The underground network of fungi creates a pervasive, intricate system that helps retain soil moisture, improving grass growth.
• Fungi in the soil responsible for mushroom growth can form symbiotic relationships with plant roots (mycorrhizae), helping them absorb nutrients and water.

Are mushrooms harmful to lawns?

Most mushrooms are not harmful to your grass but actually signify a healthy lawn. As mentioned before, their presence means there is good organic matter and fertile soil, which is beneficial to the lawn.

There are exceptions, however. Mushrooms known as fairy rings, may be harmful to your lawn.

These mushrooms are from the class Basidiomycetes and grow in a circle, hence the name. Fairy rings are problematic because they form a thick fungal mat that prevents water from seeping into the soil, depriving grass of essential nutrients. The grass in and around the fairy ring circle may die.

Fairy rings also can make your lawn more susceptible to lawn diseases that cause further problems. As the mushrooms break down a large amount of organic nutrients and release nitrogen, it causes grass to grow prolifically in giant circles with dark green rings. This overabundance of nitrogen results in succulent blades promoting brown patch and Pythium.

That said, per Vaughn Reints, SDSU Extension Horticulture Assistant, “mushrooms that are growing on living plants, especially trees, can be indicators of tree health issues, and those should not be removed without investigating underlying problems.”

What are the best ways to get rid of mushrooms?

Although mushrooms are not harmful to your lawn and typically go away when the soil dries out, it’s understandable if you don’t find them aesthetically pleasing and want to eliminate them.

Fortunately, that’s not difficult:

• Scarify or dethatch your lawn to reduce thatch, and improve air circulation through the turf.
• Aerate your lawn to loosen soil compaction and improve water and air movement into the ground.
• Clear bushes and trim tree limbs to allow more sunlight onto the lawn.
• Pick up leaves, tree trunks, twigs, and animal waste to reduce the decaying matter that mushrooms thrive on.
• Mow over them, or pick up or rake them if there is just a handful.
• Collect grass clippings when you mow or rake them afterward.
• Dig the mushroom clumps out using a garden spade or shovel.
• Apply commercially available fungicides. Follow the label instructions carefully. To control fairy ring fungi, apply fungicides containing flutolanil (Prostar), pyraclostrobin (Insignia), or azoxystrobin (Heritage, Headway, or Scott’s Disease Ex).
• Apply nitrogen fertilizer to your lawn. Nitrogen speeds up their growth and shortens their lifespan, so they’ll disappear quicker.

Note: Just because you remove the mushrooms once doesn’t mean they won’t return. “They will reappear during favorable environmental conditions,” says Aaron Steill, a specialist at Iowa State University’s Consumer Horticulture Extension. The mushrooms will disappear permanently when the organic matter they are decomposing has been exhausted.

How to prevent mushrooms in your yard

Preventing mushrooms from growing in your yard can be challenging because they thrive in organic-rich environments (which you want for your grass) and proliferate when it’s rainy and cool (how do you control that?).

However, you can take several steps to minimize their growth:

• Minimize moisture in your yard by avoiding overwatering, fixing leaky hoses, and repairing irrigation systems. Water your lawn correctly, providing moisture deeply but infrequently.
• Organic mulches, especially wood chips and bark mulch, are a natural food source for mushrooms. Use inorganic mulches, such as gravel or rocks, where mushrooms are problematic.
• Mow your lawn regularly and at the recommended height. Need help determining how high to cut your grass? Our article discusses ideal grass heights.
• Prevent thatch buildup by using slow-release nitrogen fertilizers and avoid overwatering.

FAQs about mushrooms in your yard

Will mowing over mushrooms make them spread?

Mowing over mushrooms will get rid of any you can visibly see, but it will spread their spores around, leading to more growth when the conditions are right.

Are mushrooms in my yard bad for dogs?

While many mushrooms in yards are harmless, some can be toxic to dogs if ingested. It’s challenging to differentiate between poisonous and non-toxic mushrooms by sight alone, as many toxic varieties closely resemble harmless ones. Therefore, it’s safest to assume that any mushroom growing in your yard could harm your dog.

Is there a difference between mushrooms and toadstools?

There isn’t a scientific difference or biological distinction between the two; most times, mushrooms and toadstools are used to describe different types of fungi. Edible fungi are typically called mushrooms, while poisonous types are usually deemed toadstools. Sometimes, any mushroom with a stem and a cap is called a toadstool.

Struggling with lawn mushrooms?

The presence of mushrooms is generally a sign that your lawn is fertile with a high concentration of beneficial nutrients and plenty of organic matter. Since they aren’t harmful to your grass, you don‘t have to worry about damage when they pop up on your lawn.

However, if they bother you, reach out to Lawn Love. We’ll put you in touch with a highly rated local lawn professional who can help with necessary maintenance like lawn aeration and leaf removal to keep your grass looking great and mushroom-free.

Main Image Credit: Pixabay