fairy ring
noun
1
: a ring of basidiomycetous mushrooms produced at the periphery of a body of mycelium which has grown outward from an initial growth point
also : a ring of luxuriant vegetation especially when associated with these mushrooms
2
: a mushroom (especially Marasmius oreades) that commonly grows in fairy rings
Example Sentences
Recent Examples on the Web Towering over us was a circle of 100-foot-tall redwoods, known as a fairy ring. 
Jeffrey Ball, Fortune, 28 Sep. 2021 One common disease with too much organic matter is fairy ring. oregonlive, 21 Aug. 2021 See the places where fairies and gnomes live outside on the museum grounds, dance in a fairy ring, and more. courant.com, 28 May 2021 These fast-growing descendant trees — often found growing in a circle, called a fairy ring, around the original stumps — make up 95 percent of the redwood acreage across the state. Peter Fimrite, SFChronicle.com, 30 Jan. 2020 One contends that the grass formed fairy rings itself in an attempt to survive and take advantage of limited resources in arid desert environments. Erin Blakemore, Smithsonian, 18 Jan. 2017
Jeffrey Ball, Fortune, 28 Sep. 2021 One common disease with too much organic matter is fairy ring. oregonlive, 21 Aug. 2021 See the places where fairies and gnomes live outside on the museum grounds, dance in a fairy ring, and more. courant.com, 28 May 2021 These fast-growing descendant trees — often found growing in a circle, called a fairy ring, around the original stumps — make up 95 percent of the redwood acreage across the state. Peter Fimrite, SFChronicle.com, 30 Jan. 2020 One contends that the grass formed fairy rings itself in an attempt to survive and take advantage of limited resources in arid desert environments. Erin Blakemore, Smithsonian, 18 Jan. 2017 Word History
Etymology
from the folk belief that such rings were dancing places of the fairies
First Known Use
1870, in the meaning defined at sense 1