This could turn out to be one of the wettest Junes in recent memory. Rainfall in the Metro area has been moderate to over abundant and as a result you may be seeing in your lawn what I am seeing in mine – mushrooms. I have a great crop of mushrooms sprouting in my front lawn, right where our elm tree used to be and where the roots are still decaying underground. Mushrooms sprouting may lead some to be concerned about the health of their lawns, but rest assured the vast majority of mushrooms are not associated with lawn diseases.
Mushrooms that sprout in lawns are the fruiting bodies of fungi in the soil. They usually appear after heavy rainfall or watering from early spring to late summer. They feed on organic matter in the soil, usually from rotting wood from the roots or stumps of fallen or removed trees, but also other organic material such as stems, grass blades, leaves and thatch. Mushrooms can also develop in lawns of newly constructed homes if wooden construction debris has been buried in the soil.
There is nothing you can spray on your lawn to get rid of mushrooms. They will continue to sprout as long as the organic matter is present in the soil. The fungi actually contribute to the recycling process of returning the decaying wood to nutrients in the soil. Once the organic matter is gone the mushrooms will disappear. Unfortunately, for newly fallen and large trees with extensive root systems this can take many years. In the meantime, all you can do is knock the mushrooms over with a rake and discard them.
Mushrooms can also feed on heavy lawn thatch, so if you have mushrooms growing where there is no knowledge or evidence of decaying wood in the soil, you may be able to solve the problem by dethatching the lawn. Other ways to reduce mushrooms in your lawn are to rake in the spring and remove dead grass and plant material, and aerate in the fall to reduce soil compaction and improve drainage.
The one exception to the idea of mushrooms not being associated with lawn disease are fairy rings — dark green circles of grass with poor or dead grass in the middle. Mushrooms will sprout around the outer ring of grass after a heavy rain or watering. Fairy rings start small and grow larger every year. When they are small, fairy rings do not have much effect on the lawn, but as they grow the grass in the middle is inhibited from growth and sometimes dies. The cause of this is a heavy concentration of fungus in the soil (of which the mushrooms are the fruiting bodies) that inhibits the growth of the grass. Fairy rings are very hard to control. If you can’t live with them you can try digging out all the soil within and one foot outside the fairy ring and one foot deep. Replace with fresh soil and reseed. This is a lot of work and not always successful unless you are able to remove all the fungi from the soil. You may decide to live with the fairy rings in which case you can try fertilizing the area several times a year with nitrogen.
Mushrooms can range from not poisonous to very poisonous and unless you are sure which is which, it is advisable to remove them in order to keep them out of reach of young children and pets. However you decide to deal with your mushroom problem, remember not to eat them unless you are absolutely sure they are safe. There is no easy way to separate the edible mushrooms from the poisonous. Don’t buy into the myths about judging them by their color, watching to see if insects will eat them or checking with a silver spoon. The tasty, spongy morel is the State Mushroom and pops up in fields, forests and wherever there is decaying organic matter around the state in the early spring, generally the end of April to the middle of June. Morels are considered a delicacy by mushroom hunters, however even experienced mushroom hunters must beware of the false morel – it can kill. (True morels are hollow when cut open and false morels are dense and solid.) Follow the mushroom hunters’ mantra “when in doubt, throw it out” and remember all mushrooms can be eaten – but some kinds only once!