All swamp grass is not alike. Students of botany divide them into three distinct groups: sedges, reeds, and true grasses. If for some bizarre reason you would ever be called upon to tell them apart, the mnemonic device is: "sedges have edges, reeds though are round; grasses have nodes from the top to the ground". Looking at the stem, sedges are triangular in cross-section, reeds are round in XC and true grasses have nodes (where the "leaves" arise from) up and down the stem. Sedges and reeds have leaves only at the bottom. This really impresses girls.