It’s finally spring, and our cool-season turfgrass lawns are rapidly greening up. However, there may be a grassy weed living in your lawn that is much slower to awake from its winter rest. Nimblewill (Muhlenbergia schreberi) is most obvious this time of year. While dormant, its appearance is that of very light tan-colored, “puffed up” patches (the patches look like buff-colored scouring pads). When nimblewill greens up to a grayish or bluish green in late spring, its appearance is more inconspicuous. It tends to go dormant fairly early in the fall as well and therefore may be noticed then, too.
Nimblewill is a warm-season perennial grass that is fairly common in Illinois. Typically found growing in shady or wet lawns and landscapes, it creeps by aboveground, horizontal stems that can root at the nodes and readily form patches. Its leaves are smooth, quite narrow, and short compared to many grass species. Individual plants look almost wiry. In fact, another name for this grass is wire-grass. A closer look at this plant reveals a very short, membranous, toothed ligule. The leaves are rolled in the bud. The flower is a fine, slender panicle.
In Illinois, nimblewill may be confused with zoysiagrass, which has a similar growth pattern. However, dormant zoysiagrass is more of a golden tan in color, and unless planted it is very unlikely to suddenly appear as a weed.
Although easy to identify this time of year, nimblewill is best controlled in the summer, when it is actively growing. Proper cultural practices can significantly aid in controlling lawn weeds. Be sure that watering, fertilizing, and cultivating are done properly and at the right time.
Many lawn weeds can be controlled with herbicides. Unfortunately, there are no selective herbicides available for the control of nimblewill. Nonselective herbicides such as glyphosate can be used, but keep in mind that nontarget desirable plants such as bluegrass may be seriously injured or killed if contacted by glyphosate. Also, to be effective, glyphosate should be sprayed on green, actively growing plants. Because nimblewill patches are obvious now, make a note of where they are located. Later in the growing season, when it comes time to treat actively growing nimblewill, extend spray coverage beyond the immediate patches, as creeping stems are prone to lurk in these areas. Stolons missed by applications may form subsequent patches.
Many of our cool-season turfgrasses are dormant during hot summer days. Meanwhile, nimblewill is actively growing and enjoying the lack of competition. This unbalance can allow nimblewill to be a serious weed problem. Therefore, controlling patches while they are smaller is recommended. For up-to-date lawn weed-control recommendations, consult with the University of Illinois Extension publication, Illinois Commercial Landscape & Turfgrass Pest Management Handbook, as well as the Home Yard and Garden Pest Guide.