Disease

Fairy rings

Rings of dark green or dead grass, often with mushrooms, made by fungi growing outward through the soil.

What you'll see

• A circle or arc of darker green, faster-growing grass in the lawn.
• A ring of brown, dying grass, often with mushrooms along the edge after rain.
• Dry, water-repellent soil and white fungal threads under the thatch in the dead band.

Why it happens

Soil fungi feed on buried organic matter such as old roots, wood and thick thatch, and spread outward in a ring. Some release nitrogen and make a green band; others stop water soaking in.

How to fix it

1. Spike or core-aerate the ring and water it deeply to wet the dry soil.
2. Feed and water the rest of the lawn well so the ring blends in.
3. Rake or mow off mushrooms to tidy the lawn; it won't remove the fungus.
4. The only cure is digging out the soil 12 inches (30 cm) deep and 2 feet (60 cm) beyond the ring, which is rarely worth it.

Keep it from coming back

• Dethatch when the thatch is more than 1/2 inch (1.2 cm) thick.
• Keep the lawn well fed and watered, since stressed lawns show more damage.
• Clear buried wood and roots before seeding or sodding a new lawn.

Sources

• UC IPM: Fairy ring
• RHS: Fairy rings
• University of Maryland Extension: Mushrooms and slime molds in lawns

General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.