Fairy ring

Marasmius oreades and other soil fungi

also called fairy rings

Rings or arcs of lush, dark green grass, sometimes with a bare scorched band and a circle of toadstools; the fungus lives in the soil and the ring widens year on year.

Fungus Disfiguring Soil-borneAirborne spores

What you'll see

A ring or arc of unusually dark green, lush grass appears in the lawn.
A band of dead, bare, or scorched turf may sit just inside the green ring.
A circle of toadstools can spring up around the ring in damp weather.
The soil beneath the ring becomes dry and hard, resisting water.
The ring slowly widens outwards each year.

Why it happens

Fairy rings are formed by soil-living fungi such as Marasmius oreades, whose thread-like mycelium grows outwards in a circle. As it breaks down organic matter it releases nitrogen that greens the grass, while the dense mycelium can make the soil water-repellent and scorch the turf.

They favor lawns on sandy or thatchy soils rich in buried organic matter such as old roots or tree stumps, and the toadstools show most in warm, damp weather.

Treating it

Mask the greener ring by feeding the whole lawn evenly with nitrogen.
Spike the affected band deeply and drench with water plus a little washing-up liquid to rewet the repellent soil.
Brush off toadstools before they shed spores, and keep pets and children away as some are toxic.
For a stubborn ring, dig out the affected soil well beyond the edge and returf with clean soil.

Keeping it away

Reduce thatch by scarifying and keep the lawn aerated.
Remove buried wood, old roots, and stumps before laying turf.
Feed and water evenly so the grass stays uniformly vigorous.
Avoid importing soil or turf from ground known to carry the fungus.

Who gets it

Lawns and fine turf, especially on sandy, thatchy, or organic-rich soils.