Mulching is a great step to take in your garden to improve moisture retention, prevent weeds and warm the soil for your crops. Though some store bought mulches are expensive, there are several mulching materials that you may be able to find in your garbage can or recycling bin.
“It all works,” said Matthew Wallhead, ornamental horticulture specialist and assistant professor at the University of Maine Cooperative Extension. “Newspaper or cardboard would be options, especially early on for weed suppression.”
Sonja Birthisel, postdoctoral research associate at the University of Maine, said that cardboard is especially effective.
“You can use cardboard in the path between garden beds if you have a backyard garden to keep weeds under control,” she said. “It’s less expensive than if you wanted to do wood chips.”
Because cardboard and newspaper are high carbon materials, Birthisel said some gardeners may worry about binding nitrogen in the soil and making it less accessible to plants.
“It’s possible that that can happen in the top layer but in the long term as long as you have something going down deeper it shouldn’t affect more than the top layer,” she said.
Wallhead warned, however, that cardboard can make it difficult for water to reach the soil, so gardeners should be extra cognizant of that when determining whether they have watered their garden plots enough. Newspaper can be a little more permeable than cardboard.
If you plan to use shredded paper or newsprint, Birthisel said to make sure you have a thick enough layer.
“That newspaper is going to break down quicker than wood or wood chips,” she said. “You’re going to want several inches of newspaper to make sure you’re really blocking incoming solar radiation.”
Kate Garland, horticultural specialist at the University of Maine Cooperative Extension, said she will lay newspaper, paper bags or cardboard under a layer of straw or bark mulch to serve as an extra weed barrier.
“Soak the newspaper first, lay the newspaper around the seedlings within a couple inches of the stem, overlap the edges [and] put your straw right on top of that,” she said. “That will help the newspaper stay in place and just make it look more attractive.”
For direct seeded crops like carrots and radishes, Garland recommended mulching right after planting.
“It’s much easier to mulch right after seeding than trying to mulch around very young seedlings,” she explained.
Eric Gallandt, professor of weed ecology at the University of Maine, added that topping the cardboard with other mulches helps ease some of the aesthetic eyesore of newsprint in the garden. Plus, the newsprint helps you save money on more expensive organic mulches while improving weed suppression.
“You could just put it out there but it’d look terrible just by itself,” Gallandt said. “The newsprint would allow you to use a little less of the organic mulch on top and have less gaps in it. For any mulch you use, the newsprint tends to improve weed supressability.”
However, Gallandt said to look into the types of inks and glues that are used on the materials you are upcycling beforehand to make sure you aren’t adding anything toxic to the garden.
“That’d be something that you’d want to research,” he said.
Watch: How to make seedling pots from newspaper