Matthew Stevens: Without fail, mushrooms flourish in wet soil

It seems like every year, in late summer or fall, after a wet period, the same thing happens — mushrooms start to pop up in lawns and gardens.

Without fail, the phone calls start, with caller after caller wondering why the mushrooms have shown up and what can be done about them. The simple answers to those questions are that the mushrooms appear because it’s wet and there’s nothing that you can really do about it. Of course, there’s a little more to it than just that.

Mushrooms usually arise in the lawn or garden when there is a type of fungus present in the soil and moisture conditions are high. Even though we don’t see it, there are always things happening inside the soil. One of those things is decomposing of plant tissue, whether it be roots, stems or fallen leaves that have incorporated into the soil surface.

As this plant tissue breaks down, it becomes a food source on which mushrooms can grow and thrive. They are particularly prone to develop in areas where trees have been cut down, as the rotting roots underground contribute to mushroom growth. This can even happen several years after a tree has been removed.

Although there are many different types of mushrooms that show up in lawns, there are a few that are particularly distinctive. One is the stinkhorn, a foul smelling orange mushroom. It is often long and slender and may have a dark tip. As with most mushrooms, much of its body is underground, so just removing the part that’s visible above ground won’t accomplish much.

Another common type is the mushrooms that result from fairy rings, a specific fungus that causes mushrooms to appear in circular patterns. This disease is often particularly worrisome to those who have it because of the unique pattern. However, it’s really no different than what I’ve already described.

Decaying material in the soil feeds the mushrooms and they grow when there is a lot of moisture present. The growth just happens to be in a recognizable shape rather than random or scattered throughout the lawn.

Though not a mushroom, slime molds are fungi that also grow on decaying organic material under wet conditions. These often show up in flower beds where hardwood mulch is used. Slime molds can be quite unpleasant to look at — in fact there is one called dog vomit fungus because that is exactly what it looks like. Although unsightly, this fungus won’t harm plants and can be eliminated by removing the mulch it grows on.

Many mushrooms are nothing more than a nuisance in the lawn and garden. They can be mowed or picked. However, they’ll return as long as the conditions stay wet. You may notice them in low-lying areas or in other poorly drained spots where extra water seems to collect.

Improving the drainage or diverting water away from these locations might help with long-term mushroom control. Digging them out and replacing the soil in areas of heavy infestation is also an option, but probably one that would only be practical in very small areas. Herbicides such as roundup are not effective on mushrooms.