Lawn mushrooms in your yard? Here is what you need to know

Ted Smith
UW Extension

What do fairy rings and dog vomit have in common? They are forms of mushrooms and fungi that we saw last year in Park County. Whether they have a magical/mystical connotation or a putrid description, they are the fungus among us. This year’s wet spring may be a repeat of 2023 and a similar outcome.
Mushrooms, fungi, and slimes are formed when a susceptible host (organic matter), a favorable environment (wet, humid weather), and a pathogen (spores) come together. Without all three, the conditions are not favorable for growth. This is very similar to planting a garden or a lawn, the exception being the use of seeds, not spores. The organic material that nourishes fungi may be old tree roots or stumps, dead vegetation, buried lumber in the soil, crawl spaces, mulch, grass clippings, or wood decking.
Spores are all around us in the soil and air, and remain dormant until the above three growing conditions are suitable. Dormant spores, like weed seed, can last for years, even decades. Dry years suppress their emergence. Along with warm, humid weather, extended shade conditions and poor air circulation promote growth. These factors lead to the unpredictability of the fruiting structures of fungi emerging from the host.
Mushrooms and fungi are the fourth part of the carbon cycle, the process that moves carbon between plants, animals, and microbes, minerals in the earth, and the atmosphere. Besides the consumption and breaking down of organic matter for nutrient release, mushrooms can be an indication of healthy soil.  It also can show the lawn is getting plenty water.
Some the mushrooms that emerge are of the poisonous type. Care should be exercised if your home has small inquisitive children or pets. Removal would be prudent. Another negative sign of mushrooms is over-watered or poorly drained soil. A circular arrangement of mushrooms with a dark green ring, many times is identified as fairy rings. This can affect any type of grass. This a hydrophobic fungal disease that causes the grass to die for lack of moisture, allowing mushrooms to grow. The diameter of the circles can range from 3 feet to over 100 feet.
If the crowns (or bases) of the grass is not dead, heavy watering, nitrogen application (maximum of 1 lb. /1000 feet2) to the inner circle, or over-seeding can jump start regrowth and lessen the visual effects of the damaged lawn. Fairy rings are not necessarily destructive to the yard and if you don’t mind the temporary color difference, no control is required.
Here are 10 strategies to control lawn mushrooms:
1.) Ensure proper drainage
2.) Adjust irrigation time and amount for current moisture conditions
3.) Fertilize to promote a healthy lawn
4.) Aerate and/or dethatch the lawn
5.) Dig up and physically dispose of the mushrooms
6.) Use DIY fungicides after removing mushrooms, such as add a few drops of dish soap to the area, or apply a mixture of 5 tablespoons of vinegar per I gallon of water to the area that had the mushrooms
7.) Remove dead tree roots, wood, old mulch, decaying leaves
8.) Mowing: Caution, that may also spread the spores to more areas or another area
9.) Fungicides are an option, results vary
10.) Environmental conditions will change and they disappear on their own time
(Ted Smith is the UW Extension horticulture program coordinator for Park County.  He asked us to consider running this information because he received many calls last year and already this spring from people in the Big Horn Basin who noticed mushrooms and fungi appearing overnight in their yards.)