About 70, see text.
The family Cyperaceae, or the sedges, is a taxon of monocot flowering plants that superficially resemble grasses or rushes. The family is large, with some 4,000 species described in about 70 genera. These species are widely distributed, with the centers of diversity for the group occurring in tropical Asia and tropical South America. While sedges may be found growing in all kinds of situations, many are associated with wetlands, or with poor soils.
Some well-known sedges include the water chestnut (Eleocharis dulcis) and the papyrus sedge (Cyperus papyrus), from which the Ancient Egyptian writing material was made. This family also includes cotton-grass (Eriophorum), spike-rush (Eleocharis), sawgrass (Cladium), nutsedge or nutgrass (Cyperus rotundus, a common lawn weed), the large genus of Carex, and white star sedge (Rhynchospora colorata).
Features distinguishing members of the sedge family from grasses or rushes is that members of the sedge family have triangular stems (with occasional exceptions), and their leaves are spirally arranged in three ranks (grasses have alternate leaves forming two ranks)[1][2][3].
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