Plastic and fiber weed barriers for gardens are big on promise and price but they have their drawbacks. Plastic never breaks down, and its nonporous properties means that the ground beneath is not getting fed by the mulch breaking down on top of it. Fiber weed barriers can tear and get pulled through mulch easily, becoming unsightly. An inexpensive and green alternative is to use old newspaper as a weed barrier under your mulch. Newsprint is porous, decays slowly and will work just as well as anything you can buy.
Define your garden space if you are designing a new area. (If laying newspaper as a weed barrier in an existing space, you may skip this step.) Dig your edging with a flat spade, cutting away the grass and leaving a couple of inches of indentation, or put down stones or other border for the new space.
Layer newspaper over the grass or garden area. Make sure the pages overlap and your newsprint barrier is thick, at least 5 to10 sheets in thickness.
Water thoroughly. Your paper needs to be heavy and wet to smother out and kill the grass and weeds beneath. Add more layers of paper as needed, and continue to water.
Place mulch a couple of inches thick, covering the newspaper. Mulch is not only more attractive than the paper but will help keep the paper moist. As the newsprint and mulch both decompose, they will add needed nutrients to your garden.
Avoid digging in your area for at least a month to give the barrier ample time to kill anything growing beneath.