Q: What causes green circles of grass that grow higher and darker than the rest in my meadow? They appeared very quickly, just after I cut the area last week. This is a mystery to us.

A: You are seeing fairy rings. They’re not gathering places for magical beings, just areas where decomposing fungi have been fast at work. As they eat the clippings where you mowed, nitrogen fertilizer is released, causing the lush grass. Oftentimes mushrooms will appear after a rain.

Your fairy rings are classified as Type 2, having green grass but no ring of dead grass nearby. This is good news, because a ring of dead grass caused by fairy ring fungi is difficult to treat.

When seen in lawns, a light application of fertilizer to the whole area will mask the green rings. In your case, you can leave the rings alone and let nature take its course.

See
Fairy Ring: Control on Warm Season Turfgrasses
and
Preliminary Observations on Fairy Ring Control