A large clumping wetland grass growing out from short rhizomes and creeping runners, stands up to 120cm in height and will sometimes form a dense sod.  The stems are thick with light brown bases that are wrapped in old leaves with a sponge-like texture. The upper leaves are wide and flat, extend longer than the stalk, and are noticeably seperated by whiteish knot-like cross walls.  Inflorescence are long and cylindrical, carrying both male spikes (4-7 at top of stem) and female spikes (2-4 on lower stems).  The fruits are yellow-green or straw coloured, are inflated and egg shaped with multiple ribs, and narrowing to a beak with two points and three stigmas.