Each Autumn I get two visits from these fungi in my garden. They seem to be part of circles with a radius of nearly 1 metre - hence the “fairy ring”. They last a couple of days, then disintegrate, and presumably this is just long enough to set and distribute spores. I understand the whole circle is part of a single organism. www.forteantimes.com/articles/141_faeryrings.shtml
They came again a year later, but not in the same grouping.