Common names: Yellow nutsedge, yellow nutgrass, nut sedge, chufa, earth almond, northern nutgrass
Latin names: Cyperus esculentus L.
Family: Cyperaceae (Sedge family)
General Description
Perennial sedges are among the most troublesome weed species globally across agronomic crops, horticultural crops and turfgrass. Because nutsedges look like grasses (Figure 1), they are often referred to as “nutgrasses”. They can be differentiated from grasses by looking at their stems. Grasses have round or flat stems, but nutsedges have triangular stems (Figure 2). They typically reproduce through tubers, which can remain viable for up to 10 years. However, they are also capable of reproducing via seeds. From April to mid-July, tubers begin to sprout, and seedlings start to emerge. Nutsedges can also be propagated by underground stems called “rhizomes”. They frequently thrive in well-drained, sandy soils as well as in wet locations.
Figure 1. A yellow nutsedge plant taken from a strawberry field (Photo by J. Cerritos).
Figure 2. Nutsedge stems are triangular in cross-section (Photo by J. Cerritos).
Identification and Biology
Several nutsedges species exist, however the most common and troublesome ones are yellow nutsedge (Cyperus esculentus L.) and purple nutsedge (Cyperus rotundus L.). Both are perennials that spread asexually through rhizomes (Figure 3). These rhizomes extend from the mother plant to form new shoots or tubers. Tubers are initially rounded, ridged, and white but they gradually turn brown and black (Figure 4). They form at the ends of rhizomes and can be found within the top 6 inches (15 cm) of the soil profile. These tubers overwinter in the soil and once conditions are favorable, they break dormancy and sprout. Yellow nutsedge leaves are yellow-green, have a long, tapered point and grow in clusters (Figure 5).
Figure 3. The structure of a yellow nutsedge plant (Photo by S.L. Meyers).
Figure 4. Yellow nutsedge tubers (Photo by S.L. Meyers).
Figure 5. Yellow nutsedge plants growing on plasticulture strawberries (Photo by J. Cerritos).
Yellow and Purple nutsedge
They are often mistaken for each other due to their similar appearance. However, yellow nutsedge has yellow-green leaves with leaf blades that come to a sharp point. In contrast, purple nutsedge features deep green leaves that end in an abrupt point (Figure 6). The inflorescence (or flower structure) of yellow nutsedge is straw colored, whereas the inflorescence of purple nutsedge is reddish-purple (Figure 7). In Indiana, yellow nutsedge is far more common.
Figure 6. A purple nutsedge leaf (left) and yellow nutsedge leaf (right) (Photo by S.L. Meyers).
Figure 7. Floral structures of purple (left) and yellow nutsedge (right) (Photo by S.L. Meyers).
Management
Yellow nutsedge can be a challenging weed to control due to its ability to reproduce easily through various propagation methods.
Sanitation and Exclusion
Because nutsedge can reproduce through plantlets, rhizomes, and tubers, it is important to remove visible nutsedge parts and soil before moving equipment from nutsedge-infested fields to those without nutsedge (Figure 8).
Figure 8. Nutsedge plants hang on the back of a sweet potato harvester and can easily be moved within or between fields without proper sanitation (Photo by S.L. Meyers).
Mechanical Control
While cultivation and hand removal are potential control options, they are only effective in the short term. Nutsedges can regrow if the plants are not entirely removed, including both the stems and root systems. Cultivation is most effective when performed on small nutsedges that have not yet developed tubers and have underdeveloped root systems. Repeated mechanical tillage can help suppress nutsedge, but there is a risk of spreading the plants and tubers to other fields via the equipment.
Plastic mulches are commonly used for weed control in some horticultural crops. However, these mulches do not fully suppress yellow nutsedge, as the plants can grow through the plastic (Figure 9).
Figure 9. Yellow nutsedge plants growing through white plastic mulch in a strawberry field (Photo by J. Cerritos).
Biological and Cultural Controls
Many animals find yellow nutsedge tubers to be palatable. In fact, yellow nutsedge is marketed and sold to wildlife food plot enthusiasts for turkey. It is said that hogs will root in the soil for the tubers as well. On small, diversified farms, rotating livestock to infested fields may decrease the amount of tubers in the soil. Summer cover crops can also be an effective option, as they compete with nutsedge for light, water, and nutrients. Choose covers that grow quickly and/or that will grow above the nutsedge canopy. Buckwheat and sorghum-Sudan grass are two common choices, but others will work as well. If it is an option, crop rotation can be an effective management strategy. Rotating from vegetables to agronomic crops, where there are more effective control options, can decrease the nutsedge population significantly in a single season with greater control after 2 to 3 years (Figures 10 & 11).
Figure 10. A sweet potato field infested with yellow and purple nutsedge (Photos by S.L. Meyers).
Figure 11. The same sweet potato field, figure 10, the next year following soybean harvest (bottom). The soybeans received applications of glyphosate and halosulfuron herbicides. Note the decrease in nutsedge shoot density (Photos by S.L. Meyers).
Herbicides
Chemical control using herbicides with active ingredients such as sulfentrazone, halosulfuron, and S-metolachlor can aid in managing these weeds. Soil-applied herbicides should be sprayed and incorporated before nutsedge emerges. If the label allows it, sequential applications of postemergence herbicides 2 weeks apart can increase nutsedge control compared to a single application. Unfortunately, grass-selective herbicides such as clethodim, sethoxydim, and fluazifop do not control nutsedges. Yellow nutsedge is a persistent weed that may require multiple herbicide applications for effective control. Always read the label and follow approved rates and guidelines for application. Visit mwveguide.org for more information about herbicides registered in the vegetable crops you grow.
References
Meyers, S. L., & Shankle, M. W. (2015). Nutsedge Management in Mississippi Sweetpotatoes. Mississippi State University Extension. https://extension.msstate.edu/sites/default/files/publications/publications/p2909.pdf
Neal, J.C., Uva, R.H., DiTommaso, J. M., DiTommaso, A. (2023). Weeds of the Northeast. Second edition by Cornell University.