#3. What Do I Put on the Bottom of a Raised Garden Bed?
First of all, if you have Bermuda grass or another aggressive type of grass, I recommend removing it from under your raised bed. If you have other less-aggressive grass, lay down cardboard (or several layers of newspaper) first on top of the grass and then put the raised bed’s soil on top of that. Do this in the Fall so that the grass below the cardboard and raised bed will die off over the winter.
Using this layer of cardboard on the bottom of your raised garden bed helps to prevent weeds from growing through and even acts as compost. This adds organic material to the soil, promoting healthier soils that the roots of your plants can grow into.
By avoiding plastic weed barrier fabric, you are actually creating a more sustainable environment for your garden. A completely enclosed raised garden with impenetrable weed barrier fabric on the bottom requires you to amend and feed the soil because it is a closed system. The cardboard method, however, connects to the existing environment below it and is therefore a more sustainable gardening option.
You may also consider adding a layer of grass clippings, leaves and other organic material before you put down the layer of cardboard to also turn into compost for even healthier raised bed soil.