A wet August week in Jefferson County brings mushrooms up in almost every lawn, and every year someone asks whether the lawn is sick. Usually it is not. But there is one pattern that is worth taking seriously: a ring or arc, expanding a little every year, that greens up first and then leaves a band of dead grass behind it. That is fairy ring, and it behaves differently.
Ordinary mushrooms
Mushrooms are the fruiting bodies of fungi living in the soil, feeding on dead organic matter: old roots, buried wood from a tree that was removed years ago, construction debris, a thick thatch layer, or the mulch in a bed. They appear after rain because that is when the fungus fruits. They do no harm to the grass, they do not mean the lawn is diseased, and they disappear when things dry out.
The reasons to deal with them are pets and kids. Some lawn mushrooms are toxic if eaten. Rake or mow them off when they appear, and do not try to identify them for eating.
If the same spot fruits every wet spell for years, there is something buried there feeding the fungus, usually old roots or a stump. Removing it ends the mushrooms. Otherwise, wait them out.
Fairy ring
Fairy ring is caused by a group of soil fungi that grow outward from a starting point in a circle, feeding on organic matter as they go. The ring expands each year, from a foot or two across to twenty feet or more on old lawns. It shows up in three ways, sometimes combined:
- Type 1: a ring or arc of dead or dying grass, often with a dark green band just inside or outside it. The fungus has made the soil hydrophobic, so water cannot get in and the turf dies of drought in a wet month. This is the damaging type.
- Type 2: a ring of darker, faster-growing grass with no dead band. The fungus is releasing nitrogen as it breaks down organic matter, and the grass responds. Mostly cosmetic.
- Type 3: a ring of mushrooms with no visible effect on the grass. Cosmetic.
In the Big Bend, fairy ring is most common on sandy, low-organic soil and on lawns built over cleared woodland where old roots are still in the ground. Our minor lawn diseases post covers the other things that make rings and patches.
Managing type 2 and type 3
Mostly you live with them. Mowing removes the mushrooms. A light, even application of nitrogen across the whole lawn reduces the contrast of a dark green ring by bringing the rest of the lawn up to match, though on centipede that trade is not worth it. Core aeration through the ring helps water and air get in. Do not worry about it beyond that.
Managing type 1
The dead band is a water problem, so the fix is getting water in:
- Core aerate the ring and a couple of feet either side of it, heavily. Multiple passes.
- Apply a wetting agent labeled for turf to the ring, and water it in deeply. The wetting agent lets water penetrate the hydrophobic soil. Repeat every few weeks through the growing season.
- Water the ring deeply and by hand if needed until the grass recovers.
- Do not over-fertilize the dead band to force recovery. On centipede especially, that adds a second problem.
- Re-plug or re-sod what does not recover once the soil is wetting properly.
Fungicides labeled for fairy ring exist and are used on golf courses, usually applied in spring at the first sign of activity and watered in deeply. On a home lawn the results are inconsistent and the aeration-and-wetting-agent approach does most of the work. Our post on when fungicides actually help puts that in context.
The long-term fix
Fairy ring feeds on buried organic matter. Removing stumps and large roots when a tree comes down, rather than leaving them to rot under new sod, prevents most cases. On an existing lawn, reducing thatch with regular aeration and avoiding heavy nitrogen keeps the fungus with less to eat. On sandy ground, compost topdressing after aeration builds the kind of active soil biology that keeps any one fungus from dominating. See our aeration guide.
FAQ
Will fairy ring spread to the whole lawn?
It expands slowly, a few inches to a foot a year, and rings sometimes die out when they meet each other. It rarely takes over a lawn, but a type 1 ring can leave a lot of dead grass over a decade.
Are the mushrooms in a fairy ring poisonous?
Some are. Treat all lawn mushrooms as not for eating.
Can I dig the ring out?
You would have to remove soil about a foot deep and two feet either side of the ring, and replace it. It works and it is a lot of work. Aeration and wetting agents are the practical route.
Do you deal with this as part of service?
Aeration, watering adjustments and turf repair are part of the plans we build.
If there is a ring in your lawn that grows every year and leaves dead grass behind it, get in touch and we'll look at it. We maintain lawns across Monticello and out toward Miccosukee where old woodland lawns are common.