Issue 6, July 1, 2020

Yellow Nutsedge Identification and Control

Overall, sedges are pretty good at disguising themselves as they superficially resemble grass. They blend into a lawn decently with growth that is similar to that of turf. It is the yellow-green color however, that makes yellow nutsedge noticeable. It can be found easily this time of year, unless of course it is hiding within other plants in a landscape bed. Of course, the most successful weeds learn to perfect this art.  Job well done, nutsedge growing within my rose bush.

The most commonly found weedy sedge in Illinois lawns and landscapes is yellow nutsedge (Cyperus esculentus), also known as yellow nutgrass.  However, there are many other sedges in Illinois.  You can learn more about them at  I count at least 68 of them listed!

Individual yellow nutsedge plants have upright, grasslike leaves that emerge from a fibrous root system, and scaly, white or light-colored rhizomes. The base of the plant is distinctly triangular in shape – “sedges have edges”. Grasses have round or oval shaped stems. A warm-season perennial, one yellow nutsedge plant may produce hundreds or even several thousand tubers (nutlets) in a season. 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. Most tubers can be found in the top 6 inches of the soil and a chilling period is required to break dormancy. New plants emerge from tubers from late May to mid-July. The tubers are the only part of the plant that persists over winter.

Beginning development of yellow nutsedge tuber in July – photo by Michelle Wiesbrook

Yellow nutsedge tuber in September – photo by Michelle Wiesbrook

Yellow nutsedge is grass-like but can be easily spotted with a trained eye.  Leaves emerge from the plant's base rather than from along the stem as we see with grasses. They are three-ranked, light yellow-green, 1/8 to 1/2 inch wide, up to three feet long, and have parallel veins with a prominent fold in the middle. 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, leaf-like 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. Although seed can be produced, reproduction is primarily by tubers.

Yellow nutsedge growing in turf – photo by Tom Cosgrove

Yellow nutsedge is often an indicator of poor drainage. However, it will tolerate dry sites once established. It grows in 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.

Avoiding introduction of this weed is best. When purchasing sod and soil, look for materials that are free of nutsedge. Once nutsedge is present, controlling it is very difficult after the tubers have formed due to the tubers' reproductive capacity. Therefore, control tactics should be applied before tubers are produced. Typically, we recommend this be done by July.

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. Plants pull easily after a rain. Keep in mind that tillage will spread this plant. Mow low (to less than one inch on turf species tolerant of that practice) and frequently to reduce growth from the plant base. Fertilize turf in autumn after nutsedge growth has slowed.

Chemical controls for yellow nutsedge include fumigation and herbicides. Several postemergence herbicides can be used, but total control can be difficult and such products may require multiple applications. Keep in mind that nutlets can sit dormant for many years before sending up new shoots so a careful eye on the site will be needed for several years following control. Bentazon (Basagran T/O) and sufentrazone (Dismiss) are contact herbicides and good coverage of application is essential. Sulfentrazone may be found in combination products, however, some of those labels state that yellow nutsedge suppression is to be expected rather than control. Systemic options include but may not be limited to halosulfuron (SedgeHammer, ProSedge, etc.), sulfosulfuron (Certainty), imazosulfuron (Celero), and mesotrione (Tenacity, TRIONE).  Other trade names may be available and product listing here is not endorsement.  Turf managers have reported that applications of Roundup (glyphosate) have resulted in poor yellow nutsedge control. Be sure to read and follow herbicide labels very carefully. Check to see that your particular turfgrass species is labeled for use. Product labels provide information about adjuvants and additional recommendations for controlling this weed.

For control of yellow nutsedge growing around ornamentals and in landscape beds, several of the above mentioned active ingredients (bentazon, halosulfuron, sulfosulfuron) are labeled for use in these situations. Additionally, certain products have soil activity and are absorbed by the rhizomes offering a “preemergent” control. Imazaquin (Image) can be used in this manner but the number of labeled ornamental species is limited and this product cannot be used in cool season grasses.

Adapted from previous HYG newsletter articles

Michelle Wiesbrook

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