The Sedge Family

Cyperaceae is a family of graminoid plants. They can usually be identified by their stem shape, which tends to be triangular. This has given way to a mnemonic saying, "Sedges have edges, rushes are round, grasses are jointed and hollow all the way to the ground". This is very helpful for field identification, though there is a big exception to this "rule" with Schoenoplectus, which has round stems.