This sedge looks like a grass, but has the distinct center edge in the blade that lets you know it is a sedge. Even if you were a Round-Up person, you’d have no luck eliminating the weed with an herbicide. We suggest pulling the sedge but loosing the soil around it so you can get the tubers and rhizomes through which it spreads. It will take some time:(

http://www.ppws.vt.edu/scott/weed_id/cypes.htm
Yellow Nutsedge
www.ppws.vt.edu
Spikelets occur at the ends of the solitary stems in a cluster where the flower stalks arise from a common point (umbel-like). Individual spikelets are yellow to brown in color.