In this month's episode of Field Notes , Susan Knight of UW-Madison’s Trout Lake Station describes an unusual growth pattern of an aquatic plant, reminiscent of mushroom fairy rings. Over a year ago, a colleague sent me a fuzzy photo of a lake with what looked like two rings, or rather, doughnuts, of floating plants in the middle of a lake. The plant was probably water shield, and while water shield often forms a ring around the perimeter of a lake, I had never seen a ring out in the middle of a