By Steve Borel
After a rainy period in summer, we typically see mushrooms popping up everywhere. Some people are concerned; some are curious, and some are downright irritated when these strange growths appear in landscapes.
First, we need to understand that mushrooms are produced by fungal organisms. Most fungi grow best when there is abundant moisture available, so it is typical to see increased fungal activity during and after wet weather. There is no one particular fungus that is responsible for all the mushrooms we see. A wide variety of fungi produce many different sizes, shapes and colors of mushrooms.
Fungi play other roles in the environment. The vast majority of fungi do not cause plant disease or are actually beneficial to plants. Some fungi help plants. Fungi kill nematodes and insects in the soil that might attack plants’ roots, for instance. Beneficial fungi even help protect plant roots from pathogenic fungi.
A large group of fungi called saprophytes is critical to the health of our landscapes. Saprophytic fungi eat and digest (decay) dead organic matter. These fungi help keep dead organic matter from building up in nature. For the gardener, they are vital in the process of turning organic matter into compost. When you incorporate organic matter into the soil of a bed, it is the saprophytic fungi that help break it down into vital humus and release the nutrients it contains. These fungi also decay organic debris in the lawn — grass clippings and dead leaves that would otherwise accumulate and choke out the grass.
Saprophytic fungi are always present in our lawns and gardens, quietly decaying organic matter. We just don’t usually see them, although you may occasionally see the white threads of saprophytes when you move decaying mulch or compost. But after a generous period of rainfall, many of these fungi make their presence known by sending up mushrooms — lots and lots of mushrooms.
It’s important to understand that the mushroom is not the fungus. It is simply a growth from an organism living in the soil and the layer of organic matter on the soil surface. Mushrooms are the reproductive structures (called “fruiting bodies”) of certain fungal organisms. Their role is to produce spores and release them. You can kind of think of them like flowers.
You can remove the mushrooms you see, but the organism producing them is still there. Simply removing the mushrooms, then, does not keep them from coming back.
So, saprophytic fungi and the mushrooms they produce are not harmful to your lawn or other plants in your yard, and you need not have any concern in that regard.
Because it is possible some of the mushrooms may be poisonous, they should be promptly removed when they appear in situations where pets or small children may have a chance to consume them. For everyone else, ignore them or mow them down.