Answer: Yanking out Bermuda grass by hand is not always effective because the grass spreads by producing underground runners that take root and produce new plants, with the new plants producing runners, and so on.
You can use an herbicide containing the funny-sounding chemical fluazifop, which kills only grass and will not harm landscape plants. Grass-B-Gon by Ortho is one product that contains fluazifop.
You also can spot-kill Bermuda grass inside the planter by using an herbicide that contains glyphosate, such as Roundup by Monsanto. First, water the grass and apply the herbicide while the grass is growing. You have to be careful not to spray this herbicide on any other plants, because the chemical will kill them. One trick is to take a piece of poster board or cardboard and use it as a spray barrier between the plants you want to protect and the grass you want to kill. Wait a few days after applying the chemical and water the treated area again. If grass still is growing, apply more herbicide. You may have to repeat the process several times.
Hope this information helps!
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