Cardboard Connection

Use: Plain brown corrugated cardboard (broken-down boxes and pre-cut rolls work equally well), craft paper, or newspaper. Black ink (such as used in newspapers) is generally soy-based and non-toxic.

Do not use: Anything glossy, bleached white, with a waterproof coating, or with large amounts of colored inks.

Remove: All tape, plastic labels, and staples.

Get enough to cover your entire sheet-mulching project area with at least one layer of cardboard, extending 4-6” beyond the edge of the grass on all sides. Get enough to allow separate pieces of cardboard to overlap by 4-6”, and to thoroughly cover all gaps. Two layers are more effective than one, though will take longer to decompose.

Contact stores that sell large or bulk items, such as appliance stores, furniture stores, bicycle shops, and cabinet shops. You can also purchase plain craft paper or rolls of corrugated cardboard.

Sheet mulching is a slow, easy, and fun way to remove grass so you can start gardening! This lawn removal brochure explains the process.

Very little research has been done on sheet mulching. One commonly cited study suggests that cardboard can temporarily reduce gas exchange, but the test was done on buckets of water, not soil. The study author has also said that any effect cardboard may have on soil is likely similar to wet leaves on the forest floor. This suggests that sheet mulching mimics anaerobic conditions commonly found in nature, and thus is not a cause for concern. Any effect it has is also very temporary, as it typically decomposes within a few months.

 Plain untreated cardboard is safe to use for soil in which you are planning to grow food. Heavy metal exposure primarily results from paints, pigments and other colorants used in printing processes, and the amounts that have been found in cardboard are extremely small and well within safety standards. Plain uncoated cardboard will have even less, if any, and also does not have preservatives in it. If your untreated cardboard is not decomposing after a while, it is likely just because it is too dry.

 Sheet mulching is most appropriate for temporary projects such as lawn removal. Cardboard repels water when it dries out too much, so is not recommended for weed suppression around growing crops (though drip irrigation underneath may work–more research is needed).

 Cardboard or paper is easy and convenient, especially for small strips of lawn, but it is not essential. If your space allows, a 10-12″ layer of arborist wood chips works equally well.