Answer: Johnson grass is a nasty perennial weed and to eliminate it completely you need to dig out all the roots. If your flower beds are overtaken by the weed you may need to remove all of your plants and treat the weeds with a vegetation killer such as RoundUp. Once the weeds are dead, dig them out, roots and all. Then cover the bed with weed barrier cloth and cut holes in it to plant your perennials. After planting you can place bark or decorative rock over the weed barrier. The weed barrier will last many years and effectively keep any weeds from sprouting in the bed.
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