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Layering cardboard is the first step in building a new community garden.

Some neighbors deliver home-baked apple pies. Mine tote cardboard. It’s not unusual to spot a smiling person in a bathrobe dragging the box from a newly purchased appliance across the lawn to deposit onto our front porch. Skeptical at first (is she charmingly eccentric or just plain weird?), the folks on my block have seen me begin a number of now-thriving garden beds with a thick layer of cardboard. A few of them are now successfully using the method in their own gardens.

Why cardboard is better

Whether you’re concerned about environmental impact or gardening on a budget, cardboard is the perfect alternative to traditional landscape fabrics made from polypropylene, polyester, or similar polymers. Here’s why:

  • It’s abundant—and free. Recycle boxes from your own purchases, scavenge from your neighbors or workplace, dumpster dive, and make friends with the loading dock crew at your local big-box appliance store. I live within a mile of our community recycling drop-off center, and I’m not shy about hovering near the cardboard bin to secure large pieces destined for the compactor.

    Cardboard abundance from a restaurant dumpster

  • It’s water-wise. Cardboard absorbs water, keeping it in your garden bed where it’s needed.
  • It’s truly biodegradable. Cardboard decomposes quickly (2-3 months), unlike polypropylene, which does not biodegrade and eventually entangles spreading plants.
  • Worms love it. Cardboard is tasty worm food, and the resulting castings (waste) make for a soil amendment rich in essential minerals and enzymes. Those of us with hard-packed clay soil appreciate how the worms’ burrowing action aerates (adds oxygen) and drains the soil.
  • It’s recycling made easy. By using cardboard you rescue and  reuse material that might otherwise go into a landfill.

Two more weed barrier options

There are two new commercial weed barrier options. One is essentially a long roll of brown paper, slightly thinner than paper bag material. I tested one of these products; the paper tears easily but it does cover a lot of ground quickly. It’s biodegradable, minimally packaged, and a good option if you need something right away and don’t mind paying for it.

The other is marketed as biodegradable polypropylene and is currently the subject of much debate. I’m a gardener, not a chemical engineer. The Biodegradable Products Institute has good information, including this article on sorting through facts and claims, written by a professor of chemical engineering and materials science at Michigan State University.

Tips for using cardboard as a weed barrier

  • Use brown cardboard only—avoid white, brightly printed or waxed.
  • Remove tape and staples.
  • Large pieces of thick, corrugated cardboard like those from appliance boxes will cover a larger area and provide a more substantial weed barrier.
  • Be sure to overlap edges 6-8 inches.
  • Water the cardboard well before you add mulch.
  • Poke holes into the wet cardboard to add plants.

Will you eventually get weeds? Yes. No barrier, including cardboard and landscape fabric, will stop wind-born seeds or runners that creep over from another area. But if you’ve also included deep mulch on top of the cardboard, you will find that unwanted plants are easier to remove.

Permaculture principles at work

  • Use and value renewable resources and services
    (Reduce dependency on scarce resources)
  • Integrate rather than segregate
    (Stack functions to capitalize on how things work together)
  • Use small, slow solutions
    (Local resources and responses, manageable scale)

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