Cladium (Fen-sedge, Sawgrass or Twig-sedge) is a genus of large sedges, with a worldwide distribution in tropical and temperate regions. These are plants characterized by long, narrow (grass-like) leaves having sharp, often serrated (sawtooth-like) margins, and flowering stems 1–3 m tall bearing a much-branched inflorescence. The number of species it contains is disputed, with different authors accepting between two and 60 species as distinct. Like many plants found in wet habitats, it has deeply buried rhizomes that can produce tall shoots with dense canopies.
Cladium jamaicense, or saw-grass, is common in marshes and savannas throughout the tropical Americas. One typical and well-known area of extensive saw-grass growth is the Florida Everglades; sawgrass is the plant referred to by the descriptor, "River of Grass". Like many species of the Everglades, C. jamaicense grows in extremely infertile conditions, particularly wet sites that are low in phosphorus. Dense sawgrass beds are intermingled with other vegetation types. Together they produce a rich array of habitats that support the biological diversity of the Everglades. American Alligators also use sawgrass to build nests.
Cladium mariscoides, or twig-rush, is also a wetland plant, but is found further north, and in other kinds of wetlands including fens, wet meadows  and pond shores . Owing to such specific habitat requirements, it is quite rare in the northern states such as Minnesota. "Finding a self-sustaining population of C. mariscoides on a lake shore is indeed a very rare event in Minnesota".
- Cladium californicum (S.Watson) O'Neill – California Sawgrass (Southwestern North America); doubtfully distinct from C. jamaicense.
- Cladium chinense (Eastern Asia); doubtfully distinct from C. mariscus.
- Cladium jamaicense (C. mariscus subsp. jamaicense) – Sawgrass (Warm temperate and tropical New World, except where replaced by C. californicum)
- Cladium mariscoides – Smooth Sawgrass (Temperate North America)
- Cladium mariscus – Great Fen-sedge, Saw-sedge (Europe, Asia, Africa)
- Cladium nipponense (Eastern Asia); doubtfully distinct from C. mariscus.
- Cladium procerum – Leafy Twig-sedge (Australia)
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