Cyperus arundinaceus

About

Dulichium is a monotypic genus of sedge containing the single species Dulichium arundinaceum, which is known by the common name threeway sedge. This is an aquatic or semi-aquatic plant of the lakes, streams, and ponds of the United States and Canada. It has a wide distribution across the two countries, though noticeably absent from the Dakotas and from the Southwestern Deserts.

Summary from Wikipedia