Most gardeners are familiar with herbicides that can be used to eliminate broadleaves (i.e., dandelions) from grasses (i.e., lawn). They may not be as familiar with herbicides that can take grasses out of broadleaf plants like shrubs. There are two major weed killer types that are used to kill grassy weeds in broadleaf plants. On the commercial side, the trade names for these products are Fusilade and Poast. Homeowner labeling is more diverse. I have seen Fusilade sold under the names of Ortho “Grass-B-Gon” and Poast is sometimes sold to homeowners under the Poast label but I’ve seen it more commonly sold as “Bonide Grass Beater,” “Fertilome Over the Top II Grass Killer,” “Hi-Yield Grass Killer” and “Monterey Grass Getter.” There may be other trade names, too. Fortunately, you can identify the product by the common chemical name listed on the label. Fusilade’s common chemical name is fluazifop, and Poast’s is sethoxydim.
If you decide to use one of these products, read the label carefully. Often, a crop oil must be added to the spray solution for the herbicide to work well. Some grassy weeds are not controlled such as bromegrass and sandbur. Mature tall fescue also is not controlled though seedling tall fescue is. Established bermudagrass is knocked back but rarely killed.
Though both these products can be used over the top of numerous broadleaf plants (including iris), there are some differences in labeling. For example, if you need to control grasses in strawberries, choose Poast because it has a seven-day waiting period before harvest. Fusilade cannot be used within one year of harvest. (Ward Upham)
