Mushrooms in a lawn are unsightly and dangerous. Sometimes proper care of a lawn creates an environment that encourages growth of mushrooms. In other cases the mushrooms migrate from neighboring lawns. Either way mushrooms that appear in lawns require removal before they spread and become a larger problem.
The fairy ring fungi creates circles and semi-circles in the lawn. Sometimes there are mushrooms in the rings and sometimes not. These rings are called fairy rings because long ago it was believed that mushrooms grew in places where fairies danced. More than one type of fungus creates these rings, including Marasmius oreades and Lepiota.
The fairy ring fungi grow in a circular mat in the soil. The active portion of the mat is on the edges. This active edge releases extra nutrients into the lawn, causing increased growth in a ring shape. The interior of the mat is sometimes so dense that water cannot get to the lawn roots, so the lawn has a tendency to brown or die in the center of the ring.
Solutions to the rings include adding water and fertilizer to make the rest of the lawn just as green. If there is dying lawn in the interior of the ring, aerate or remove the spot or cores manually to allow water to penetrate the fungal mat. Remove the leftover plugs and cores from the lawn after these procedures. Proper watering causes the lawn to green up again. If the lawn is completely dead inside the ring, it is best to remove the sod and soil to a depth of 1 foot, including the ring and 18 inches beyond the ring. Afterwards, replace and reseed the soil in this area.
One of the biggest problem with mushrooms in a lawn is the risk to children and pets. These family members are likely to eat any mushroom they find in a lawn. Since most wild mushrooms are poisonous, mushrooms in the lawn require control. You can remove mushrooms manually, although this will not kill the underlying structure of the fungus.
Mushrooms in New Sod
A common type of mushroom that appears in newly laid sod is Panaeolus foenisecii. This small mushroom appears because of the frequent watering required by a sod installation. When the sod is established and watering is reduced, the mushrooms will go away.