Are Fairy Rings of Mushrooms mentioned anywhere?
TVTropes on Geometric Magic says of The Dresden Files:
[Fairies] can use [magic circles] as well, usually constructed from the famous "fairy ring" of mushrooms.
I don't remember seeing any mention of "fairy ring" in the books... And Google isn't finding anything either.
Are mushroom circles used without calling them fairy rings? Or is my memory accurate and they really don't appear?