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You Can Grow It: What to do with mushrooms in your lawn or garden

KTVB's Jim Duthie explains what makes mushrooms grow and what you can do about them.

BOISE, Idaho — With recent rainy weather, you've probably noticed a lot of mushrooms popping up in parts of your lawn and garden. They're pretty common this time of year, and you might be wondering if they are harming your grass or causing problems for your children and pets.

KTVB's garden master, Jim Duthie, explains what makes mushrooms grow and what you can do about them.

With an increase in temperatures comes an increase in lawn watering; combine that with the recent rain and it makes for perfect mushroom-growing conditions 

Mushrooms, which are actually the fruit of beneficial fungi in the soil, contain seed spores that are carried by wind, animals, and even our shoes and lawnmowers. They thrive on nutrient-rich decaying wood and other organic materials.

When conditions are right, usually a mixture of cool and moist weather, established underground fungi will shoot up its version of a flower full of spores in order to spread.

Mushrooms do not have detrimental effects on grass, however; in fact, they can be beneficial to have in your lawn, as the extensive root systems help hold water, which allows them to break down organic materials and add nutrients to your grass. 

While they can be a little unsightly in the middle of a nice green lawn, most of these mushrooms - or toadstools as they are sometimes referred to - are not the kind you can eat. They are fairly easy to keep under control though, for those concerned about pets or small children being around them.

Mushrooms can be eliminated by knocking over the visible part, or by raking or mowing over them. Be warned, however, that that may spread the spores around causing more mushrooms to grow.

Instead, try pulling the mushrooms up and throwing them into a garbage bag rather than composting to limit the spread of spores. Be sure to wash your hands after handling them as well.

The best way to prevent mushroom growth is to starve them by reducing available water and providing more drainage. Aerating and dethatching the soil will also help. 

Reducing the amount of other organic material that may decompose, like leaves, grass clippings and animal waste, can further prevent mushrooms from growing. Make sure to check for buried pieces of wood or dead roots too. 

Jim Duthie recommends regularly mowing your lawn, as shorter grass dries out faster than tall grass which will keep your lawn from producing the additional moisture needed for mushrooms to grow. Also, make sure to pull up any mushrooms and rake away the pieces before mowing, to ensure the spores are not spread.

Follow that up with a nitrogen-rich fertilizer which will speed up the decomposition of organic material, limiting the amount of available food for mushrooms. 

While commercial fungicides may kill the mushrooms, they do not get down far enough into the soil to kill the fungus that produces the mushrooms. 

Occasionally, a circle of mushrooms may form, also known as a fairy ring. In most cases, removing the mushrooms and digging or aerating the area will control the mushrooms and eliminate the problem.

“The bottom line is that mushrooms won’t harm your lawn; they’re just not very pretty to look at," Jim said. "But a few simple steps to reduce the moisture and organic matter that mushrooms need to grow will help you get rid of them or keep them under control.”

In the last year or two a variety of mushroom that's new to Idaho has begun to pop up in some Treasure Valley lawns. It's called a death cap mushroom, and it's one of the most poisonous mushrooms around. Ingesting a small amount can kill a dog, cat or even a person. This mushroom is not toxic to the touch, but if ingested it will make you extremely sick and can lead to death.

Death caps can resemble some edible mushrooms, but there are some distinct differences. Death caps have white gills rather than dark ones, and they have a loose skirt-like membrane around the top of the stalk just below the cap. They also have a distinct, ammonia-like scent.

If you find any death cap mushrooms in your yard, carefully remove the heads and the stalks, bag them, and throw them away. Then wash and disinfect your hands, gloves and garden tools. 

Death caps are common in many coastal areas around the world, including the Pacific Northwest, but are now beginning to spread inland. They may have found their way into Idaho through compost and potting soil around plants brought from western Washington and Oregon.

Only about five percent of mushrooms in the wild are edible, and some of those edible varieties grow nearby in the Payette National Forest, including those delicious morel mushrooms.

Remember, do not harvest and eat wild mushrooms unless you are experienced at identifying the edible ones. Each year many Idahoans are sickened or poisoned by eating toxic wild mushrooms.

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