How do I control unwanted weeds and grasses in my lawn?

March 04, 2008 Print Friendly and PDF
Throughout the year, your yard may be under attack by various lawn weeds. These spring, summer, winter, annual and/or perennial weeds utilize valuable nutrients your lawn grasses need to thrive. Spring serves as a good starting point for ridding lawns of weeds, which will make fertilization, over-seeding, and other lawn management practices much more effective. To start, what is a weed? A weed is any plant growing somewhere you do not want it to grow. Weeds can be broken down more specifically into categories consisting of broadleaf weeds, grasses, sedges, and, finally, algae and moss. When controlling these weeds, a person must at least identify the category in which the plant resides and, better yet, identify the plant. The reason the weed type must be identified is that most herbicides used on a lawn are plant specific, meaning a herbicide that would control broadleaf weeds would have no control over grasses. An exception to this of course are nonselective herbicides, which target all green, actively growing plants. To carry this further, some chemicals that may be used to control one broadleaf weed may have no control over another broadleaf weed. This makes identifying the plant very important. There are some general guidelines a homeowner can use when shopping for herbicides to control lawn weeds. When it comes to controlling broadleaf weeds, use products that combine more than one active ingredient. Products containing these chemicals will be in a liquid form and can be used postemergent, after the weed has germinated. These products should control all broadleaf weeds. On the other hand, most grasses can be best controlled using preemergent herbicides. The exception for this would be Bermuda grass, which requires postemergent herbicide treatment. For controlling sedges, a homeowner may have better success using lime and fertilizer. However, if chemical control is still needed, herbicides can be used. For controlling algae and moss, the homeowner needs to look at liming, fertilizing, compaction, and drainage problems that might be promoting the growth of these weeds. Chemical control of algae and moss can be gained by using products containing copper sulfate. Finally, when using any herbicide or pesticide ALWAYS follow label guidelines. These products have been deemed safe under specified guidelines, so follow them to the letter. Once the homeowner gains control of weeds in the lawn, there is no better way to maintain this control than proper lawn management: watering, soil testing, liming, fertilizing, and mowing at the proper height. Contact your local Extension office about their weed identification services and for specific herbicide recommendations.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.