Pests

Mushrooms and Fairy Rings in Your Lawn: What They Mean and What to Do

Why mushrooms pop up in Northeast lawns after fall rain, how to tell harmless mushrooms from fairy rings and tree-related fungi, and the fixes that actually work (hint: fungicide isn't one).

By Alex · · 6 min read

In this guide
  1. Why mushrooms show up in lawns
  2. Three situations, three different answers
  3. What to do about mushrooms, step by step
  4. Treating a fairy ring that's killing grass
  5. What about fungicide?
  6. The rest of this month
  7. Common mistakes to avoid
  8. The bottom line

A week of cool, wet October weather and suddenly the lawn is dotted with mushrooms, or a ring of dark green grass appears with a circle of toadstools around it. It looks like a disease. In most cases it isn't, and the grass is fine. This guide explains what is going on underground, how to tell the harmless situations from the ones worth acting on, and what to do (and not do) over the next few weeks.

Why mushrooms show up in lawns

A mushroom is just the fruiting body of a fungus that lives in the soil most of the year. The fungus itself is a network of fine threads that feeds on dead organic matter and breaks it down. When the weather turns cool and damp, the fungus sends up mushrooms to release spores. That's why fall (and wet spells in summer) is peak season.

The food source is usually something you can't see. According to University of Maryland Extension, buried tree roots and stumps, buried lumber or wood chips, and similar debris can feed mushroom-producing fungi for years, even when no wood is visible at the surface. Cornell Cooperative Extension of Nassau County describes the same pattern: decomposing organic matter in the soil, such as an old stump, root or board. New-construction lots and yards where a tree was removed are classic examples.

The fungi also like a lawn that stays damp. Thick thatch, compacted soil and poor drainage hold moisture and organic material near the surface, so mushrooms are more common there.

Three situations, three different answers

Not every mushroom patch is the same. Start by working out which one you have.

What you seeWhat's likely going onDo you need to act?
Scattered mushrooms, grass looks normalFungi breaking down buried wood, old roots or thatchNo. Optional cleanup (see below)
A ring or arc of mushrooms, often with a band of darker green grassFairy ring fungusUsually not. Cosmetic in most lawns
A ring with a band of dead or dying grass, or grass that repels waterA more aggressive fairy ring that dries out the soilYes, but with soil and watering changes, not a spray
Mushrooms or shelf-like growths on a tree trunk or its surface rootsPossibly a wood-decay fungus attacking a living treeYes: have a certified arborist look at the tree

Fairy rings

Fairy ring fungi spread outward from a center point underground, so the mushrooms and affected grass form a circle or partial arc that gets wider over the years. University extension sources generally describe three looks: a ring of dead or thinned grass, a ring of extra-green grass (the fungus releases nitrogen as it decomposes organic matter), and a ring of mushrooms with no visible effect on the grass at all. The first kind is the only one that does real damage, mostly because the fungus can form a dense mat that repels water, so the grass inside the ring dries out and dies even though the lawn gets rain.

Mushrooms near trees

If mushrooms are growing right at the base of a tree, on a root flare, or directly from the trunk, don't assume it's the harmless kind. Maryland Extension notes that some wood-decay fungi actively infect living trees. That is a tree-health question, not a lawn question, so call a certified arborist, especially if the tree is large or near the house.

What to do about mushrooms, step by step

  1. Decide whether they bother you. The mushrooms will fade on their own as the weather turns and the ground freezes. Many people simply mow over them.
  2. Remove them if you have kids or pets. Wear gloves, pick or rake the mushrooms and put them in the trash, not the compost pile. This also limits spore spread. Never assume a mushroom in your yard is safe to eat or safe for a dog that likes to chew on things. If a pet or child eats one, call a vet or poison control right away.
  3. Dig out the food source if you can find it. If you know where a stump was removed or lumber was buried, digging out the wood is the one real "cure." Otherwise the fungus keeps going until the wood has fully decayed, which can take years.
  4. Cut back on the moisture. Water deeply and infrequently, in the morning. Our lawn watering guide covers the amounts. Fix low spots where water sits.
  5. Reduce thatch. More than about half an inch of thatch gives the fungus a lot to feed on. See the thatch guide for how to check, and consider core aeration next fall to open the soil and improve water movement.
  6. Keep the lawn fed. A normal fall feeding (see below) keeps the grass vigorous. Extension sources note that extra nitrogen can mask the dark-green ring type by greening up the rest of the lawn.

Treating a fairy ring that's killing grass

If dead grass is spreading in a ring, here is the approach extension services such as Washington State and South Dakota State recommend for home lawns:

  1. Loosen the affected strip with a garden fork or core aerator, going deep enough to break through the water-repelling mat. Fall is a good time because the weather is cool and the grass is recovering anyway.
  2. Water the area deeply and repeatedly. A turf wetting agent (a soil surfactant) can help water soak in.
  3. Feed the whole lawn normally so the surrounding grass grows evenly.
  4. Reseed bare areas during the fall seeding window if it isn't too late, or in spring. Our fall seeding guide explains how late is too late for your area.
  5. In severe, recurring cases, the last resort is digging out the soil to roughly 6 to 8 inches in and just beyond the ring, mixing or replacing it, and then reseeding or re-sodding. This is a big job, so only do it if the ring keeps coming back and you can't live with it.

What about fungicide?

Extension sources are consistent here: fungicides are generally not recommended for home lawn mushrooms or fairy rings. The fungus lives deep in the soil and thatch, where sprays don't reach well, and the mushrooms are only the visible part. You'd spend money and the mushrooms would likely return. If you do want to consider a product for a stubborn case, get a diagnosis from your state's extension office first and follow the label exactly.

The rest of this month

Mushrooms are a fall nuisance, but the rest of the season's lawn work still applies. Keep mowing while the grass grows, keep the leaves off the lawn (a wet leaf layer feeds fungi too, so see our leaf guide), and do your late-fall feeding with quick-release nitrogen and no phosphorus. Check your state's cutoff date before applying; New Jersey, for example, bans homeowner fertilizing from November 15 to March 1. The lawn calendar has the month-by-month list.

Common mistakes to avoid

  • Spraying fungicide. It rarely works on mushrooms or fairy rings and the mushrooms return.
  • Assuming the grass is dying. Check the grass first. Mushrooms alone don't mean damage.
  • Eating or composting wild mushrooms. Many lawn mushrooms are toxic and hard to identify. Bag them for the trash.
  • Ignoring mushrooms at a tree base. These may signal decay in the tree itself and deserve an arborist's opinion.
  • Watering more to "green it up." Extra water in cool fall weather feeds the fungi and makes the problem worse.
  • Digging out the whole lawn right away. Try the cultural fixes for a season first. Most mushroom patches never need that.

The bottom line

Mushrooms in the lawn are the visible sign of a fungus doing its job underground. Pick them if pets or kids are around, cut down on excess moisture and thatch, dig out buried wood where you can, and get an arborist to check any tree with mushrooms growing from it. Fairy rings that kill grass need a deep loosening and watering plan, not a spray. For everything else this month, see the lawn calendar.

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