Answer: Although vinegar may work to discourage unwanted seedlings, established woody plants such as yours would take a more active approach. Repeated cutting to the ground combined with smothering the roots and excluding all light with a heavy layer of mulch atop a layer of cardboard or numerous layers of newspaper might eventually kill them off. Another approach would be to use an herbicide containing glyphosate applied carefully following the label instructions. You might need to reapply it, and be sure to use the formulation for brush. Also, be very careful not to allow the herbicide to contact desirable plants.
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