Occurs almost always under natural conditions in wetlands, but occasionally found in non-wetlands. Found in most counties of peninsular Florida. A large, robust plant with scabrous stems. (Crow and Hellquist, 2000)
Flat sedges are sedges. Stems solid, often 3-angled, unbranched, leafy at base; leaf blades from tubular sheaths; inflorescences terminal (on stem tips) well above the leaves, spike-like or in many heads, branched; bracts long, leaf-like (growing around the stem just below the inflorescence); spikelets clustered, axis jointed, spikelet scales in 2 rows; fruit a 2- or 3-sided achene (nutlet).
Perennial, rhizomatous. Culms glabrous. Leaves flat, 35-70 cm (14” – 28”) x 4-9 mm (.15” - .35”). Spikelets ovoid, compressed, golden brown to brown, narrowly lanceolate. Achenes slender, brown, spongy, with swollen bases. Fruits in summer. (Flora of North America, Vol. 23)
From video: stems 2-3’ tall, smooth, triangular. Leaf-like bracts around the base of the inflorescence; some longer than the inflorescence. Spherical clusters of spikelets on short and long stalks. Spikelets are flattened, and the scales open away from the spikelet axis.
For brief control information, see Efficacy of Herbicide Active Ingredients Against Aquatic Weeds by K. Langeland, M. Netherland, and W. Haller.