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written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Shrooms! Mushrooms frequently appear at this time of year in lawns and gardens. Their presence can cause great concern, especially if there are small children or curious pets who might try eating them. A local resident called me just the other day. She was worried about some very strange looking jelly-like masses showing up in her yard. While they weren’t the typical mushroom that many local residents encounter, they were evidence of a fungus.

Before we can talk about mushrooms or toadstools in lawns, we should first talk a little about mushrooms. Mushrooms are the “flowers” or reproductive structures of fungi. When we see mushrooms, toadstools, or puffballs popping up in lawns we’re only seeing part of a fungus. Beneath the soil is the “body” of the fungus. It consists of threadlike growths called “hyphae.” These hyphae form a mass of “mycelium.”

The fungi that produce mushrooms in lawns or gardens are saprophytes that feed on decaying plant matter in the soil, such as thatch, dead tree and shrub roots, or compost. The fungi reproduce via spores produced in the reproductive structures. The spores germinate and start a new fungal bodies.

While we may not like their presence in our lawns, we should appreciate the importance of these fungi in the environment. Decay fungi are one of the primary organisms responsible for the decomposition of organic matter, such as thatch in lawns, plant refuse in compost piles, and dead wood and other plant-derived materials in soil. They’re a recycling organism that reduces the amount of dead organic matter around us and helps improve the soil.

Of course the old adage, “Out of sight, out of mind.” holds true when it comes to lawns and gardens. If fungi stayed out of sight, they wouldn’t worry us. It’s only when they produce mushrooms when the weather turns cool and moist in the fall, that we notice their presence and start to fret.

The mushrooms you encounter in your lawn or garden are simply feeding on dead organic matter. This could be thick thatch or a buried tree stump and its roots. Sometimes it might even be wood that was buried during the construction of a house. If compost or organic matter was used for soil improvement, fungi may show up if these materials weren’t adequately decayed before application.

Unfortunately, there is no easy way get rid of these fungi and their subsequent mushrooms. Removal of the decaying organic matter, such as power-raking the lawn to remove thatch or digging up a decaying stump, would solve the problem, but may not be practical or possible in every situation. There is no chemical control. Home remedies often promote treating the area with some sort of cleaning agent, such as bleach. These practices may chemically “burn” the mushrooms and adjacent plants, but fail to kill the fungi that produce them. It’s likely that the mushrooms will reestablish before long.

The simplest method to reduce the hazzard that the mushrooms pose to children and pets is to rake or mow them away as soon as they appear. If you’re still watering your lawn heavily, cutting back on your irrigation can reduce their appearance, since cool, moist conditions favor their production.

When lawn mushrooms appear in distinctive arc or ring patterns in the lawn, a “fairy ring” fungus is usually the cause. The most common symptoms of fairy ring are a ring of dead grass with darker green grass on the outside or inside of the ring or both outside and inside the ring. The ring may also be simply a ring of darker grass. Mushrooms are not always present, but most often appear during moist, cool weather in the fall or spring.

There are at least 50 to 60 different types of fairy ring fungi. They grow by feeding on decaying organic matter in the soil. The fairy ring mycelium becomes so dense that it kills grass by preventing the penetration of water to the roots of the grass. To manage a fairy ring infection, WSU Extension recommends thoroughly aerating the affected areas of lawn and then watering heavily for a period of four to six weeks. The use of a horticultural wetting agent can aid in water penetration. There are some commercial chemical products that will control fairy ring, but these are not available to home gardeners.

Fairy ring tends to be worse in poorly fertilized lawns or those growing in extremely sandy soil. Adequate fertilization, proper watering practices, and regular thatch management can diminish problems with fairy ring. A more drastic management step is the removal of all the sod (grass), followed by tilling the soil in the top six to eight inches, and then reseeding or installing new sod.

Where did the name “fairy ring” come from? You probably already guessed. Long ago people didn’t know a fungus was responsible for fairy ring. People believed that fairy rings were the result of fairies dancing in circles. A more sinister myth has them as the result of where the “devil” churned butter or lightning strikes.

Are all fairy ring mushrooms poisonous? Probably not. Unless you’re a mushroom expert, it’s best to assume that they’re all poisonous. As already noted, to prevent any possible poisoning of pets, children, or adults, rake or mow them off as soon as they appear.

What’s the difference between a toadstool and a mushroom? These aren’t technical terms, but some use “toadstool” to refer to poisonous mushrooms. Others use “toadstool” to refer to mushrooms with an umbrella-like cap beneath a stalk. By the way, not all lawn mushrooms are in the typical cap and stalk form, some look like balls, cauliflower, sponges, horns, and more.

Published: 10/15/2005 11:38 AM


written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

Now that warm weather has arrived the strange molds and mushrooms that have been showing up here and there in some area lawns and gardens should start to disappear. Our typical extended cool, wet spring conditions have been very favorable for the development of a variety of nuisance fungi.

These fungi are decay organisms that grow on rotting wood, leaves, and other organic matter in or above the soil. We are made aware of their presence because of the appearance of their reproductive structures, such as mushrooms, toadstools, puffballs, and stinkhorns. These reproductive structures produce spores that germinate and develop into thin filaments called hyphae. As the fungus grows the hyphae develop into larger fungal masses called mycelium.

The fungi derive their nutrition from dead and decaying organic matter by way of the hyphae. When the conditions are right (cool and moist) the fungi will produce spores via ‘reproductive structures.’ The spores may germinate right away if the conditions are right or they can stay around years waiting for the ‘right time.’

Slime molds are primitive fungus-like organisms that have also been showing up recently. They also reproduce by spores but their general form is a white, purple, yellow orange, or brown slimy mass or blob. When the slime mold dries out it produces masses of spores. Unlike the decay fungi we already talked about, slime molds actually feed on bacteria growing in mulch or lawn thatch.

While disconcerting and aesthetically unpleasing, mushrooms don’t pose a significant problem in the lawn or garden, except to curious children or pets that might try to eat them. Because some of these mushrooms may be poisonous, it’s a good idea to pick or rake up mushrooms and other fungal reproductive structures when they appear.

The presence of these fungi and molds in our lawns and landscapes doesn’t necessarily mean that anything is seriously wrong. In lawns, it often means that there is a layer of thatch that’s decaying. Clustered areas of mushrooms popping up in lawns and other parts of the landscape often mean there is buried wood underneath. This can be due to the decaying roots of dead trees or shrubs or rotting lumber left behind from construction.

The presence of the mushrooms throughout a lawn is often associated with wet conditions, often due to frequent or excessive irrigation. Changes in irrigation and the onset of hot, dry weather can be a simple remedy to the situation. In lawns with excessive thatch, it’s advisable to remove it with a good power-raking early next spring. If the offensive fungi are due to buried wood, the only way to find out is to dig down and check it out. Control of fungi in these situations is achieved by removal of the rotting wood. When slime molds appear in lawns, they’re pretty much remedied by raking up the ‘blob.’

There is no chemical remedy for mushrooms that are present in the lawn or landscape due to rotting organic matter. The cure is removal of the organic matter and a possible change in moisture conditions… which we have no control over if it’s due to the weather like we encountered this spring.

Note: If lawn mushrooms appear in ring or arc patterns, the problem is likely due to the fairy ring fungus that attacks lawns. Fairy ring mycelium become so thick that they smother the roots and the grass dies in a circular pattern. The fungus feeds off the dead grass roots it has killed. Sometimes these rings are simply darker green due to the nitrogen released by the decaying grass, but at certain times of year mushrooms may appear in the ring. While difficult to control, management of fairy ring is best achieved by aerating the ring area and watering it thoroughly every day for about a month. The use of a grass-type wetting agent in the ring area is also helpful.

Published: 6/24/2006 11:13 AM



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