Sedge is a grasslike plant common throughout temperate and cold regions. The genus name, Carex (family Cyperaceae), is probably derived from keiro [Greek, "to cut"], referring to the sharp leaf margins. Worldwide this taxonomically involved complex is represented by some 2000 species; in Canada by about 270, plus others of subspecific rank and several hybrids. Sedges are readily distinguished from grasses by their 3-sided, solid stems and by leaves with 3 ranks instead of 2. Within the spike, the minute individual flowers are solitary in the axils of scales. Male flowers normally have 3 stamens; female flowers (enclosed in a sac, the perigynium) have 2 or 3 stigmas. The seed, surrounded by the persistent perigynium, may be lens shaped or triangled.

Flower spikes and mature seeds are needed for accurate identification to specific or lower rank. The position of male and female spikes on the plant is another important identification characteristic. In milder climates C. pendula, grown as a garden ornamental (usually near water), is prized for its bold effect (up to 1.5 m tall) and long, drooping spikes. Also grown is Japanese sedge grass (C. morrowii var expallida), which has leaves striped white.

The hardier C. plantaginea, found wild in deciduous woods from New Brunswick to Manitoba (and south), is conspicuous with its broad evergreen leaves and purple sheaths. While sedges are of limited garden value, they are sometimes planted for erosion control. The ancient Egyptians cultivated Cyperus papyrus to provide the earliest form of paper. Today the value of sedge is most evident in its native habitat, bordering sloughs and other wet places, where it provides cover and food for waterfowl.