Using Cardboard in the Vegetable Garden

Like most gardeners, I have my share of successes and failures. My most recent disaster occurred when a deer found my fall carrots and plucked them out one by one while I slept. I put a ridiculous amount of effort into preparing that carrot bed, so now I need to cut my losses and preserve the bed’s ready-to-plant condition until spring. The best way to do this is to cover the bed with cardboard, held in place with stones, bricks, or pieces of firewood. In spring, I can lift the cardboard, give the bed a light raking, and put it to work.

Gardeners have different opinions on using cardboard in the vegetable garden, but certified organic growers can use what I call ‘clean’ cardboard – plain, unwaxed boxes with all tape and sticky labels removed, with minimal printing on the outside. According to the National Center for Appropriate Technology, “the basic components of corrugated cardboard seem to be relatively benign. Brown corrugated cardboard appears to be the least processed paper product. It therefore would have the lowest number and smallest quantity of chemical substances, compared to white, glossy, highly printed, waxed or otherwise coated cardboard, paperboard, and papers.”

Smothering Weeds with Cardboard Mulch

Besides, there are many ways to use cardboard in the vegetable garden that simply work. When I moved to my current garden ten years ago, a third of it had gone wild and grown into a tangle of nettles and blackberries, with a groundcover of poison ivy running through the whole mess. Working a section at a time, I cut back the invaders and covered the surface with several sheets of damp cardboard, with soil and pulled weeds between the layers to help maintain moisture. After a few months under cardboard, the wild things were weakened to the point where I could dig them out.

Using cardboard to create new gardening space is high on the list of recommended methods promoted by Wild Ones, a non-profit advocacy organization for native plants, because smothering surface vegetation with cardboard causes less trauma to a site compared to digging it up. Many gardeners build raised beds right on their lawns, and line the bottoms with cardboard to smother the grass – a technique that makes it possible to fill the beds and start gardening right away.

A bit of advice: Shipping tape comes off easily when cardboard is wet, so I place boxes I plan to use in the garden outside and let them get rained on before I clean and flatten them. Cardboard mulch needs to stay moist, so plan to cover it with compost or another material if you live in a dry climate. Termites are occasionally seen in cardboard mulch that is kept too dry, so avoid using cardboard mulch in parched places close to your house.

Box Cloches and Bug Traps

In addition to using cardboard mulch to protect beds from compaction or subjugate weeds or grasses, this time of year I use box cloches around parsley and other marginally hardy plants. With the open flaps securely weighted, the box cloches block cold winds and extend the picking season by several weeks.

Last fall, I discovered by accident that a small cardboard box with more cardboard layers inside, placed near my deck door, made an effective passive trap for brown marmorated stink bugs (shown in the photo at the top of the page), which are determined to come inside for the winter in 44 American states and 4 Canadian provinces. They mistake the box for a safe haven, crawl inside, and are easily shaken into a bowl of soapy water on cool mornings.

The growth of e-commerce has increased the number of cardboard boxes coming into our homes, and at least some of that cardboard can be used in the garden. If you have ideas to share that have worked for you, please post them below.