Answer: The mushrooms are appearing because of the prolonged rains which can cause soggy soils and also because there is something providing a food source for them. Often it's a decaying tree root underground but it might also be due to a heavy layer of thatch at the soil surface. Thatch is basically dead roots and rhizomes and eventually all lawns develop thatch. If the mushrooms are concentrated in just a small area of the yard, use a hand cultivator to de-thatch the area around them and pick the mushrooms. This consists of getting down on your hands and knees and "hand raking the area around the mushrooms to pull the thatch out of the turf. You'll probably notice a bunch of smaller mushrooms when you get down closer. To prevent the problem, make sure to dethatch and aerate your lawn regularly - at least every 3-4 years. Also, if your landscaper uses a mulching mower, make sure they mow frequently enough that they do not leave clumps of cut grass on top of the lawn after mowing.
This is what works for my lawn. I hope it helps with yours.
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