Cyperus lupulinus (Spreng.) Marcks  
Family: Cyperaceae
Great Plains flat sedge, sand cyperus, sand sedge
[Scirpus lupulinus Spreng.]
Cyperus lupulinus image
Gary Fewless  
Cyperus lupulinus image
Gary Fewless  
Cyperus lupulinus image
from USDA Plants website  
Cyperus lupulinus image
Cyperus lupulinus image