Large populations of yellow nutsedge (Cyperus esculentus) have developed in areas that had wet weather this past spring and early summer. Also known as yellow nutgrass, yellow nutsedge is a warm-season perennial member of the Cyperaceae (sedge) family that reproduces by seeds and from tubers (nutlets). While its natural range includes most of the United States (including all of Illinois), this North American native plant is most troublesome in the southeast, including the southern portion of the Land of Lincoln.
Life cycle and appearance. Individual yellow nutsedge plants have upright, grasslike leaves that emerge from a fibrous root system, and scaly, white or light-colored rhizomes. The tubers develop rapidly six to eight weeks after the plants emerge, usually during late July and August, and can persist for many years in the soil. Forming at the ends of rhizomes (not in chains as occurs in other sedges such as purple nutsedge), the nutlets can reach up to 4/5 inch in length. New plants emerge from tubers from late May to mid-July. Leaves emerge from the plant's base, are three-ranked, grasslike, and light yellow-green, 1/8 to 1/2 inch wide, up to three feet long, and have parallel veins with a prominent midvein. The upper surface of the leaf is shiny or waxy, and the lower surface is dull. Nutsedge leaves grow rapidly during summer; they often grow above the canopy of cool-season turf. Nutsedge inflorescences (flowers) are flat topped and multiple branched with long, leaflike bracts beneath. The inflorescences resemble burrs and occur at the end of a stout, triangular (in cross-section), yellow-green stem. Each branch of the inflorescence is composed of multiple yellow-to-golden brown spikelets, each up to 1-1/4 inches long. The inflorescences appear July to September during 12-to-14-hour days.
Ecology. Yellow nutsedge is often an indicator of poor drainage. It grows on all soil types, especially wet or moist sites or sites receiving heavy irrigation. It usually appears on soils with a pH of 5 to 7. Yellow nutsedge does not tolerate shade and will tolerate dry sites once it is established.
Control. Due to the tubers' reproductive capacity, controlling yellow nutsedge is very difficult after the tubers have formed. To control without chemicals, maintain turf density and health through proper culture; mechanically remove or pull nutsedge plants soon after germination, and increase drainage in moist or wet areas. Mow low (to less than one inch on turf species tolerant of that practice) and frequently to reduce growth from the plant base. Purchase nutsedge-free sod and soil. Fertilize turf in autumn after nutsedge growth has slowed. Chemical controls for yellow nutsedge include fumigation and herbicides. Before planting in high-value sites contaminated by yellow nutsedge, fumigate with methyl bromide. Several postemergence herbicides can be used, but total control is often difficult and such products may require multiple applications. Basagran T/O (bentazon) is a contact herbicide and Manage (halosulfuron) is a systemic product that can be used. A third option is to use products containing MSMA, including Daconate 6, 912 Herbicide, MSMA 6.6, MSMA Turf, and Quadmec Trimec Plus (2,4-D + MCPP + dicamba + MSMA). Labels for these products provide information about adjuvants and additional recommendations for controlling this pesky plant. Turf managers have reported that applications of Roundup (glyphosate) have resulted in poor yellow nutsedge control.