A: In addition to interfering with water and gas movement into the soil environment, corrugated cardboard has chemical contaminants that you really don't want in your soil or even your compost pile.
Lay cardboard, heavy paper or newspaper on the grass where the bed is to go. Fill with leaves, coffee grounds, grass clippings and straw in layers. Top with 4-6 inches of garden soil and plant.
The cardboard will fall apart long before you see the plant grow. Wet cardboard will rot within a few days. I typically start my gardens by covering the grass with cardboard and they have done well.
There's little doubt that a double layer of corrugated cardboard, overlapping about 6 inches and placed over weeds that have been mowed, then covered with compost, good organic garden soil, organic matter that will rot in place, or mulch is an excellent way to get rid of weeds.
The time it takes for this to happen depends on a number of circumstances, such as type of cardboard and the conditions the cardboard has to decompose in. With the right conditions, cardboard typically takes around 2 months to decompose naturally.
Priming Cardboard For Sheet Mulching
If cardboard is able to dry out, it's going to take a lot longer to disappear into the soil. However, in a wetter climate like mine, cardboard can rot down under mulch within just six months or so.
To start from scratch where you have an area of grass or weeds, lay a double layer of cardboard on top of the soil. Overlap the sheets of cardboard to help prevent weeds pushing through the gaps. Avoid using shiny printed cardboard, and be careful to remove any staples or parcel tape first.
Cover it with soil and mulch and you will have a restored garden bed with much less of weed problem the next season. If it is already Spring and you want to use this trick, go ahead and put the cardboard down on the surface of your soil and poke holes in it just large enough to plant your seeds or transplants.
Cardboard boxes are hydrophobic to a certain degree, and if allowed to dry out, they can prohibit water from reaching plant roots. In established landscape beds, it is best to stick to just a three-inch layer of mulch. More options for mulch can be found in HGIC Factsheet 1604 Mulch.
Using cardboard or newspaper as a natural weed barrier can allow you to kill a very large area of weeds and grass without using any chemicals or herbicides. Cardboard is applied to the area. Then a layer of mulch goes on top of that. In creating a highly fertile site, a gardener may put several layers of materials.
Don't:
Spreading a new layer of topsoil encourages root growth for both plants and grass. Laying down topsoil in early spring gives the soil time for it to settle into the earth and integrate into existing soil before planting season begins.
It is for this reason we recommend using the no-till gardening method which is building your soil upon the initial cardboard layer. You will need 6-8 inches of soil and compost to cover the cardboard.
As the material breaks down, it can affect the soil pH. As cardboard breaks down, it may temporarily affect soil pH. Some gardeners report slight pH changes, though this is generally minimal and not a significant concern for most plants.
You can line the bottom of your raised garden bed with cardboard and newspaper to block out weeds or act as a barrier against rhizomatous, weedy or invasive plants. While some may opt for landscape fabric, cardboard is a more cost-effective option.
If cardboard is able to dry out, it's going to take a lot longer to disappear into the soil. However, in a wetter climate like mine, cardboard can rot down under mulch within just six months or so.
Walkable Ground Covers That Are Easy to Control:
Vegetables generally have shallow root systems, so a depth of 4-6 inches is typically sufficient. However, plants that produce deep-rooted vegetables, such as carrots and potatoes, may benefit from a slightly greater depth of 6-8 inches.
A garden or landscape mulched with cardboard (or heaven forbid several layers of cardboard as part of the science-free lasagna mulch method) is now covered with a tough, relatively gas- and water-impermeable material that will take some time to break down. It's hardly a mulch that's going to nurture soil life.
Yes, termites love to eat cardboard boxes. Termites love to eat cellulose, which cardboard boxes provide for them.
Instead, choose a low- or no-cellulose ground cover like: