A Fairy ring, fairy circle or elf circle, as it is also known, is the name given to the phenomenon of mushrooms growing in strange circles in the forest or on the lawn. It occurs when the fungus anchors itself in the soil, and the mycelium grows in an expanding circle. The mushrooms spread outwards as they use up the nutrients in the soil. This results in the fruiting bodies appearing at the circle’s edge as the centre is poorer in nutrients.
Sources
Woodlandtrust – What is fairy rings and what causes them? 
Discoverwildlife – What is a fairy ring and what causes mushrooms to form a circle?
Planetnatural – Fairy Ring
April 2023, TÄNKOM | Revised February 2024 RETHINK
