Sedge Grasses, Nut sedge, flatsedge, etc

Question: I have very aggressive sedge grasses (as identified by an app) that have grown very thick. I am looking for the best way to eradicate it. The attached pictures show how abundant it is. These pictures are taken in an area that will soon be a wildflower area, hopefully, so a sterile kill should be fine but I don't know. It is also growing to a lesser degree in the turf grass area. How can I get rid of it, how long does it take, and how will it effect the soil for the intended purpose of the areas (wildflower and turf grass)? Thank you.

responder: Erin Hill, PhD  Replied September 04, 2024, 2:05 PM EDT
response: This is yellow nutsedge (Cyperus esculentus). It is a native, perennial species in Michigan. It reproduces by seed, rhizomes (underground stems), and tubers (like very small potatoes). These later two make tillage a bad option for control.   In the lawn you could try Ortho's Nutsedge Killer for Lawns (active ingredient=sulfentrazone) or Sedgehammer (a.i. halosulfuron, found online only), but these are not appropriate for areas other than lawns. As with any pesticide application, be sure to read and follow all labeled instructions for maximum efficacy and environmental and personal safety.   There are not a lot of great options ridding garden areas of yellow nutsedge. The best active ingredients can persist and prevent the success of your desired wildflowers (sometimes for multiple seasons). One chemical option you could try would be to spray the area with glyphosate (found in Roundup Super Concentrate and other generics, especially at stores like Tractor Supply Company). This will likely take multiple efforts due to the population level you have (should be spaced at least 3 weeks apart to see maximum effect). The good thing is glyphosate does not remain active for plant uptake once it touches the soil, so once you have reached your desired level of control it would be safe to seed the wildflowers. Fall is a good time to treat with systemic herbicides like glyphosate as the herbicide is more readily moved into the root and rhizome system. Air temperatures need to still be above 50F on average though (think that you should still be needing to mow the lawn...that's usually a good indicator of the active plant growth needed). See more on glyphosate at the end.  If we think outside the chemical box...you could try smothering this area with heavy duty tarping or plastic (impermeable). It may take several month for success, but it could help eliminate the issue. If you go this route, I recommend taking the tarp off for a couple weeks during good growing conditions and observing any resurgence before attempting to plant you desirables.   Those are the options I can think of. If you have any questions, please let me know.   More on glyphosate from my files... When using products containing glyphosate there are a few important points to consider. First, as with any pesticide, remember to read and follow all labeled instructions. Second, glyphosate is a broad-spectrum herbicide, meaning it will injure or kill other plants contacted during application, so care is needed to avoid green plant material, exposed roots, and injured bark of desired plants. Third, glyphosate is relatively safe in the environment when used as labeled. It adsorbs strongly to soil in most cases (i.e. clay and organic matter), allowing even sensitive crops to be planted shortly after application; meaning no carry over issues are expected. Fourth, glyphosate alone can take up to 14 days to show full activity under ideal growing conditions. Retreatment of the area may be needed depending on the degree of infestation. Glyphosate is most effective for perennial control in the fall but can be applied anytime the plants are actively growing (temperatures consistently above 50F). For woody species, periods of heavy sap flow in the spring may not be effective times to treat. Finally, glyphosate is getting harder to find in the consumer market (i.e., big box stores) and Roundup brand products have been changing their active ingredients (even though the labels look similar) and moving away from glyphosate. Roundup Super Concentrate as of the summer of 2024 still has glyphosate only as the active ingredient. There are also generic glyphosate products available at stores like Tractor Supply Company. Be sure that the product you choose has only the active ingredient glyphosate or glyphosate + pelargonic acid. Products with additional active ingredients may have other unwanted effects and may delay the planting of other plants in the coming season(s).

responder: The Question Asker Replied September 04, 2024, 3:07 PM EDT
response: Erin, thank you for your quick and thoughtful reply. I just want to clarify something. Your use of the term “garden” caught my attention. My wildflower area isn’t a garden per se. It is a few thousand square feet of what used to be lawn that I want to convert to native wildflowers. I doubt that this distinction makes a difference with respect to your your reply. Is that right?    Bill Hall <personal data hidden>    From: ask=<personal data hidden> on behalf of Ask Extension  Sent: Wednesday, September 4, 2024 2:05:45 PM To: Bill Hall  Subject: Re: Sedge Grasses, Nut sedge, flatsedge, etc (#0153847)

responder: Erin Hill, PhD  Replied September 04, 2024, 5:22 PM EDT
response: Bill, thank you for the clarification. The future wild flower area would not be an ok place to spray the sedge targeting herbicides (i.e. Ortho Nutsedge Killer for Lawns or Sedgehammer). It would be ok to use the other tactics I mentioned though (e.g. glyphosate prior to planting wild flower or tarping...though it's so large maybe not feasible or at least not all at once or maybe you could find a used vinyl billboard tp upcycle??).

responder: The Question Asker Replied September 05, 2024, 8:28 AM EDT
response: Thank you!    Bill Hall <personal data hidden>   From: ask=<personal data hidden> on behalf of Ask Extension  Sent: Wednesday, September 4, 2024 5:22:27 PM To: Bill Hall  Subject: Re: Sedge Grasses, Nut sedge, flatsedge, etc (#0153847)