Umbrella flat sedge
This non-native sedge is sometimes grown as an ornamental, and has become naturalized in wet, disturbed sites from the central and southern peninsula of Florida. Like some other Cyperus species, this one has relatively long narrow pointed spikelets that have 2 rows of tan overlapping scales. Umbrella flat sedge is native to Africa, but escaped cultivation. It blooms from the sumemr to fall (Wunderlin, 2003).
For brief control information, see Efficacy of Herbicide Active Ingredients Against Aquatic Weeds by K. Langeland, M. Netherland, and W. Haller.
Stems clump-forming, solid, triangular, to 4 1/2 ft. tall, to 3/4 in. wide near base; leaf blades none, just sheaths wrapping stem base; bracts of inflorescence conspicuous, leaf-like, a clusster of 10-25, mostly longer than the inflorescence; inflorescence a central spikelet cluster including 15-25 stalked clusters, each cluster having 8-15 spikelets; spikelets long and thin, to 3/8 in. long, obvious overlapping scales, 15-30 flowers; nutlet brown, 3-angled, tiny