Instructions
1Use landscape fabric to prevent weeds and grass from germinating. If you're in the planning stage of your flowerbed project, you can include landscape fabric. Lay the fabric over cleared soil and cut slits for the plants you plan to add. Install your plants and irrigation system and then add mulch over the fabric. You may still need to weed or pull the stray blade of grass, but you'll greatly reduce the amount of weeds and grass in your beds.
2
Build a bed. This needs to be done before you plant. Mark the intended location and dig down 9 inches into the soil. Line the hole with thin plastic sheeting. Add 2 to 3 inches of gravel and then fill the rest of the hole with soil. Add metal edging around the perimeter and plant your flowers.
3
Add a block border to your bed. Dig down 6 to 8 inches around the perimeter of an existing bed. Clear the hole of all grass roots and line the hole with plastic sheeting. Install cement blocks or bricks in the hole, creating a perimeter of block around the bed. Top the "wall" with decorative block or brick.
4
Add newspaper and mulch to your bed. In early spring, before planting, lay down a thick layer of newspaper pages. The layer should be 1/2 to 1 inch thick. Wet the paper thoroughly. Immediately add a thick layer of mulch, such as bark or straw, and wet the mulch. Wait two to three weeks before planting. You should be able to dig through the mulch and paper to plant your flowers. You will still need to weed and pull the occasional blade of grass, but the paper and mulch will deter most of it.
5
Use a grass herbicide. Herbicides such as Roundup kill off weeds by killing the root. If you do decide to use an herbicide, use one designed to kill grass, not just weeds. Apply the herbicide directly to any grass that crops up in the bed, taking care not to spray your flowers. This will not prevent new grass from invading your flower beds, but it will kill grass as it crops up. You can also use an herbicide around the perimeter of your bed to kill encroaching grasses.