Wandering clumps are usually found in grassy areas and if someone steps on them they temporarily become disoriented and have no idea where they are.  Landmarks may appear that they are missing or in the wrong direction, roads look unfamiliar and everything seems strange. These creatures may be related to pixies. The effects of these tiny turfs can be broken by turning your clothes inside out or carrying a piece of bread in your pocket.
* photos courtesy of Arthur Spiderwick's Field Guide