Newspaper is a cheap, abundant and useful mulch. And it’s safe. You can ignore outdated cautions about newsprint containing lead because newspapers got the lead out decades ago. And the amount of hydrocarbons in colored inks is insignificant.
As a mulch layer under a decorative material such as bark chips or stones, newspaper smothers weeds and sod more effectively than the decorative material alone. And unlike some landscape fabrics and weed barriers, newspaper breaks down completely so you don’t have to extricate it in five years, when it’s shredded and roots are tangled in it.
How quickly a layer of newspaper mulch breaks down varies greatly depending on several factors. The rate is faster if the soil is rich in microorganisms, if your region is damp or you water often, or if temperatures are warm but not hot. Experiment to find what works best in your garden. As a starting point, if you live in a warm, damp climate, make your layer about five sheets thick. If your climate is dry or cold, use two sheets. Make the layer thicker if you want it to last more than a season or if you’re trying to smother an aggressive plant, such as a lawn of Bermuda grass or St. Augustine.
When using newspaper mulch, keep these pointers in mind:
• Slick inserts are safe, but their size and slickness makes them harder to work with than regular newsprint.
• Cover the newspaper completely with a decorative mulch. Exposed newspaper turns brittle quickly especially if it gets damp and then dries. Then it’s prone to breaking up and blowing around.
• Don’t cover seeds with newspaper—they can’t push through it.
• On a slope, the covering of decorative mulch is more likely to slip downhill with newspaper under it, so cover newspaper with a thicker layer of decorative mulch than you would on flat ground.
• Because newspaper is high in carbon, it could set off the chain of events among soil microbes that temporarily reduces the amount of nitrogen in the soil immediately below the mulch. The deficit should not affect established plants, but might make young, small plants turn a bit yellow. If so, treat them to a spritz of an organic foliar fertilizer.