They look like grasses but aren't.
They have "reduced morphology," which means they're hard to identify.
But not only are sedges and rushes an indicator species of the health (or not) of wetlands, you, too, can be stricken with "sedge fever"!
Sedges and Rushes of Minnesota: The Complete Guide to Species Identification is written by Welby R. Smith, photographed by Richard Haug, and published by the University of Minnesota Press.