Botanically called Cyperus croceus, globe sedge is a perennial plant with flower-bearing stems. It has fibrous roots with flat, deep green, smooth leaves, and seed heads comprising of several spikelets. Each spikelet has a long stalk with a round cluster of seeds at the end. The small seeds disperse and scatter to different parts of a lawn or yard with a breeze. They grow into unattractive weeds, and compete with flowers and grass for water and nutrients. It is best to kill the weed while it is still dormant, before the seeds propagate.
Walk through your lawn to determine where the weed is present. This weed resembles grass, but has a triangular or three-sided stem. Notice where it exists in your lawn and demarcate with powdered chalk, if necessary.
Apply a strong pre-emergence herbicide such as Metolachlor to the affected area late winter or early spring, before the seeds sprout. This herbicide is specifically formulated to kill globe sedge grass. Follow the label directions for proper application directions.
Apply a post-emergence herbicide such as Bentazon to kill globe sledge grass if the seed sprouts and the weed appears. Follow label directions for application rates. Reapply the herbicide over the area after 10 days to two weeks.
Mow the globe sedge grass down as close to the ground as possible. Water the grass slightly, and pour sugar over the area to strengthen the nutrient-holding soil microbes, so it becomes difficult for the weeds to access nutrients.
Water the area again so the sugar melts. Sprinkle sugar around the globe sedge weed every three to five days. The globe sedge plant will begin to die within two weeks.