Related Topics: [ wetlands] Sedges are perennial herbs common to most fresh water wetlands. Superficially they resemble grasses, but are really very different. The easiest way to tell a sedge from a grass is by feeling the stem. If the stem is flat or rounded, then you've probably got a grass or a reed. If the stem is clearly triangular, then you've got a sedge. Bulrushes, which are often codominant with cattails, are a type of sedge. The main way in which they differ from most sedges is their very substantial height.