What is this grassy weed?

Asked August 24, 2020, 11:24 AM EDT

I think this is quack grass, but not sure. I definitely want to get it our of my lawn, but not sure how to do it. I am sending three pictures. Two show the plant - reddish at the crown, wide leaves compared to turn grass. The other shows the seed head.

Saginaw County Michigan

1 Response

This is barnyardgrass (Echinochloa crus-galli). It is an annual species that was introduced to Michigan and can be found throughout much of the state. I generally think of seeing it along roadsides and in farm fields, but I have seen it infesting turf grass this year too (probably more common than I thought). This grass reproduces only by seed, so one of the keys to preventing future infestations will be to remove it before it can produce seed (i.e. ASAP based on your photos). Pulling the weed is effective, especially if you don't have a large infestation. If you do have a larger infestation you can use a herbicide that has the active ingredient quinclorac in it. This can be found in products such as BioAdvanced All-In-One Lawn Weed and Crabgrass Killer, Ortho Weed B Gon + Crabgrass, and Preen One Lawncare, to name a few. These products will only harm annual grassy weeds and broadleaf species, but should not affect your desired turf grass if used as directed. To prevent emergence of this weed in the future you can also use a preemergence herbicide in the spring, such as Scotts Turf Builder (a.i. pendimethanin), Menards Crabgrass preventer (a.i. dithiopyr), BioAdvanced Crabgrass Killer for Lawns (a.i. fenoxaprop). These will all target the plant as it emerges from the seed and prevent successful emergence. With any herbicide or pesticide application alwasy remember to read and follow all labeled directions.

After you have achieved your desired level of control the work isn’t over. You need to do two important things. 1) Make sure you have a robust/vigorous stand of grass in your lawn to create a competitive environment for weeds, including barnyardgrass. Practices could include re-seeding areas where the grass stand is thin (check the label of any herbicides used to see if you need to wait to plant seeds), fertilizing the grass (early-spring and/or early-fall), watering when conditions are dry, and increasing your mowing height (3.5” is ideal usually). 2) You need to be on the lookout for weeds emerging from seed. Some weeds can linger as seeds in the “seed bank” of the soil for decades! Controlling these weeds could include the use of a preemergence herbicide (e.g. products targeting crabgrass control as discussed above) or manual removal of emerged plants. More information on lawn care from the MSU Turfgrass Team can be found on the following website: https://www.canr.msu.edu/home_gardening/lawns/