(News article for May 1, 2021)
People sometimes find that yellow or purple nutsedge has become a problem in the vegetable garden or lawn. A closely related plant, green kyllinga, is also a common weed in turfgrass.
Sedges are neither grasses nor “broadleaf” (dicot) plants but are in a plant family of their own. They’re characterized by stems that are triangular in cross-section. If you rub one of their stems between your fingers, you can feel that it has three edges. Most sedges tend to grow in wet areas.
People often call yellow and purple nutsedge “coco” or “nut grass.” These are perennial plants that survive from year to year. One thing that makes them problematic is that they form “nutlets” (tubers) underground and can regrow from these or from underground stems (rhizomes).
If nutsedge goes unmanaged, it can spread quickly. Under favorable conditions, over 4 million tubers can be produced on one acre in one season.
Green kyllinga is also a perennial sedge. It also spreads by rhizomes but does not form tubers. It typically grows to a much shorter height than nutsedge.
As always, good cultural practices are an important part of preventing weed infestation in lawns. Good cultural practices include mowing at an appropriate height, fertilizing at recommended times and rates, and maintaining soil pH in the optimum range for the turfgrass that you have.
Avoid overwatering the lawn or garden, since this can favor yellow nutsedge and kyllinga.
If a small amount of nutsedge is present, it can be dug out. Since tubers and rhizomes can grow as far as 14 inches below the surface, dig deeply. Also dig 8 to 10 inches to the side of where you see any plants. If you just remove the tops of mature nutsedge plants without digging, tubers will remain in the soil and may resprout.
Young nutsedge plants don’t form new tubers until they have 5 to 6 leaves, so repeatedly hoeing or otherwise removing young plants can help prevent nutsedge from spreading.
There are herbicide options for selectively killing nutsedge and kyllinga in common warm-season turfgrasses (centipedegrass, St. Augustinegrass, bermudagrass, and zoysiagrass).
Herbicides with halosulfuron-methyl as the active ingredient have both post-emergence and pre-emergence activity on yellow and purple nutsedge. In other words, they can both kill plants that already have aboveground growth and help prevent plants from emerging from the soil.
SedgeHammer+ and Martin’s Nutgrass Eliminator are halosulfuron-methyl herbicides sold in quantities appropriate for home lawn use. Regular SedgeHammer (without the “+”) and several generic halosulfuron products for turfgrass are sold in larger quantities.
For green kyllinga, sulfentrazone is one of the more effective chemicals. This also has some efficacy against nutsedge but does not work as well as halosulfuron-methyl for that purpose. Home lawn products with sulfentrazone include Bonide Sedge Ender and Ortho Nutsedge Killer for Lawns.
Another option for kyllinga is imazaquin (Image Kills Nutsedge Concentrate). Imazaquin is also effective on purple nutsedge but less so on yellow nutsedge.
Abovementioned halosulfuron-methyl and imazaquin products can be used in some non-turf landscape areas, as well.
Herbicide options for home vegetables gardens are more limited. Commercial vegetable growers often use halosulfuron-methyl products such as Sandea, Profine 75, or Stadia. Home gardeners can purchase these, but they’re available in quantities that home gardeners may find quite costly.
For vegetable gardens, one option is to leave an area that’s heavily infested with nutsedge out of production for a season and apply a glyphosate product to nutsedge at the rate indicated on the label for tough or hard-to-control weeds. Glyphosate is systemic and if applied correctly will move from leaves down into the rhizomes and some tubers. (Since leaves need to be present for the herbicide to be absorbed, this needs to be done when nutsedge is actively growing.) Plants can still regrow from tubers that had not yet sprouted when glyphosate was sprayed, and multiple applications will likely need to be made as new growth emerges. This approach won’t necessarily eliminate all tubers from an area but will reduce the population.
Before purchasing any herbicide, read the label to make sure it’s appropriate for your situation, and follow label instructions when using the product.
Let me know if you have questions.
Contact Mary Helen Ferguson.
Yellow nutsedge. (Photo by R. Strahan)
Purple nutsedge seedhead. (Photo by R. Strahan)
Purple nutsedge. (Photo by R. Strahan)
Green kyllinga. (Photo by R. Strahan)