Weed of the Month: Yellow Nutsedge (Cyperus esculentus)
Posted: June 12, 2012
Distinct Looking Nutsedge
Yellow nutsedge is very distinct looking. The stems are three-sided, and appear triangular in cross section (“sedges have edges”). The leaves have a thick mid-vein and are very waxy and shiny. All of the above ground plant parts are light yellow-green in color, which stands out among darker green ornamental plants or cool season turfgrasses. In lawn situations, it grows faster than the grasses. Yellow nutsedge has a shallow fibrous root system that produces nut-like tubers underground as storage organs for the carbohydrates produced by photosynthesis. It can also produce fine, thread-like rhizomes that give rise to new plants.
Yellow nutsedge can be difficult to manage. While the plants pull out easily, most of the tubers are left behind, as are the rhizomes. In a location with damp soil, changing the environment by improving drainage may be impractical or cost prohibitive. There are effective herbicide treatments, but they must be used very carefully in landscape beds where yellow nutsedge grows closely with ornamental plants. Non-selective post-emergence herbicides such as glyphosate (Round Up, Eraser, many others) or glufosinate ammonium (Finale) are limited to precise spot treatments in landscape beds. Selective post-emergence herbicides include bentazon (Basagran T/O), halosulfuron-methyl (Sedgehammer) and sulfosulfuron (Certainty). Basagran and Certainty can be applied over-the-top of listed ornamental plants according to label directions; Sedgehammer cannot be used for over-the-top applications. Basagran, Sedgehammer and Certainty are all labeled to control yellow nutsedge in cool season turf. For pre-emergent applications, Pennant Magnum (S-metolachlor) is an option for all growing sites.