Controlling Yellow Nutsedge in Lawns

By Jim Crawford, MU Extension Natural
Resource Engineering Specialist
I have been receiving many inquiries this spring about a fast growing, yellowish, grass like weed in home lawns.  It grows faster than the surrounding lawn so it is quite noticeable shortly after mowing.  The culprit is yellow nutsedge.
Yellow nutsedge is a relatively common problem in lawns, especially in wet years or in lawns with irrigation.  Even though it is dry now, we had adequate rainfall in the spring to promote growth of this weed.  Although it looks much like a grass, it’s official classification is a sedge.  Unlike grasses, sedges have triangular stems, and the leaves come off the stems in three different directions as opposed to two directions for grasses.  Yellow nutsedge is pale green to yellow and grows rapidly in the spring and early summer.  Because of this rapid shoot growth, it sticks up above the rest of the lawn only a few days after mowing.  This weed is a good indicator of poor drainage, but it can be introduced into well-drained sites through contaminated topsoil or nursery stock. 
As with many weeds, nutsedge is less competitive in a dense, healthy lawn than in an open, poor lawn.  Increasing soils infiltration/ drainage is a good way to help control this weed.  If you have a larger area infested with nutsedge, core aerating your lawn this fall will help improve your lawns infiltration and thus reduce the favorable habitat for this weed. 
Nutsedge is difficult to control culturally because it produces numerous tubers that give rise to new plants.  Pulling nutsedge will increase the number of plants because dormant tubers are activated.  However, it is possible to control nutsedge by pulling, but you must be persistent. If you are, eventually the nutsedge will die out. 
If you decide persistent pulling is not for you and you wish to treat with an herbicide, it would be better to leave the nutsedge plants undisturbed so the herbicide can be maximally translocated to the roots, rhizomes, and tubers.  Several herbicides are labeled and available for nutsedge control.  Sedge Hammer, which used to be called Manage, is the most effective and safe for most turf grasses.  It is also the most expensive, but if an infestation is not too severe, one application should take care of the problem. 
The Sedge Hammer label says to apply it after nutsedge has reached the three- to eight-leaf stage.  Waiting until this growth stage apparently results in improved translocation of the active ingredient to the underground tubers and rhizomes.  However, research has shown that the application should go down by June 21.  If the initial spray is after June 21, mature daughter tubers may be stimulated to grow.  Small packages of Sedge Hammer are available to homeowners. Using a non-ionic surfactant with the Sedge Hammer will give better control.   Make sure you fully read, understand and follow all label directions before you apply any chemical to your lawn. 
For more information on this or other weeds in your lawn, check out our guide sheet G6750 Home Lawn Weed Control on line at http://extension.missouri.edu/explorepdf/agguides/hort/g06750.pdf or stop by your county Extension Center to obtain a copy.