Cyperus bipartitus

About

Cyperus bipartitus, also known as slender flatsedge, river cyperus, or shining flatsedge, is a species of flowering plant in the sedge family Cyperaceae. It is native to the Americas, from southeastern Canada to northern Argentina. In the United States, its season runs from July to October but little else is known about its ecology. It is often confused with Cyperus diandrus, both of which have chestnut-brown scales protecting the flowers. It may also be confused with Cyperus gracilis, another species known as "slender flatsedge". The name "shining flatsedge" refers to the shiny appearance of its heavily pigmented floral scales.

Summary from Wikipedia