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By Sam Burbach, Education & Programming Coordinator – 04/14/2021

With so many amazing plant varieties available today, sometimes we have more plants than we have the room to grow them! Luckily, creating a new garden bed can be quite simple utilizing a sheet mulching technique – no digging out of turf grass or use of chemical herbicides required! This method smothers out grass utilizing cardboard and a layer of soil/compost/mulch, and once the grass has died it will decompose in place and add organic matter back into the new garden bed.

There are a few things to consider prior to choosing a location for a new garden bed:
  1. Always call or click before you dig! It is a good idea to have underground utilities located in your yard prior to deciding where to put a garden bed so that you don’t end up creating your garden somewhere you won’t be able to dig. (https://www.illinois1call.com/)
  2. When replacing lawn with a garden bed it can be helpful to dig out a patch of the turf several inches deep so you can see the soil conditions prior to establishing your bed. You will be adding a few inches of new soil and/or compost to the top layer but you will likely want to avoid areas with heavy clay or rocks near the surface. If the soil under the turf is less than ideal, you can always build a raised bed on top of it utilizing this technique to smother the grass.
  3. If you have specific plants that you want to grow, especially fruits or vegetables, make sure the area you choose receives an adequate amount of sunlight to meet the growing needs of the desired plants. You’ll also want to consider how much natural water the area receives – is it a low area that is constantly wet or does it tend to dry out quickly? – and whether you have a close water supply to utilize. Figuring out what light and water your new garden bed will receive will help you determine what you can grow.

Once you find a good location for your new garden bed, you’re ready to get started!

Here’s what you’ll need:
  • Thick cardboard (non-glossy or waxed, and remove all tape)
  • Topsoil and/or compost
  • Edging material (optional but helpful)
  • Lawn mower or string trimmer
How to create a new garden bed over lawn:
  1. Prepare your site by mowing the grass short or cutting it back short with a string trimmer. If there were any weeds in that location that had gone to seed you will want to remove those from the site, but the grass clippings can stay in place.
  2. If you want to edge your new garden bed, or even build a raised bed, put the edging material/raised bed in place.
  3. Lay the cardboard down on top of the cut grass making sure to overlap the cardboard so that the grass and weeds will be completely smothered. Some grass or weeds may poke through, but most will be smothered. As the grass dies, it will decompose and add organic matter back into the soil.
  4. Spray down the cardboard with water.
  5. Cover the cardboard with at least 4-6 inches of top soil and/or compost. If you are making a raised garden bed you may need more. To help calculate how much soil/compost you will need, you can use this calculator: https://www.inchcalculator.com/soil-calculator/
  6. Spray down the soil/compost with water to help it settle.

You can plant in your new garden bed right away or give it a few weeks for the grass to start to die and the cardboard to start to break down. Starting a new garden bed using this technique is a great idea early in the spring before you are ready to plant or even in the fall so that the bed has all winter for the grass and cardboard to decompose. If you are ready to plant in the garden right away, just punch holes into the cardboard where you need to plant so that the roots can get through that layer and anchor into the ground rather than just in the top few inches of soil/compost you have added. If you do plant in the new bed right away, keep an eye out for grass growing through near the hole you punched in the cardboard and pull out any grass that is able to grow up through the bed.

Whether you plant in your new garden right away or let it sit fallow for a few weeks to a few months, the grass and cardboard will decompose and help create great soil to grow in! With such an easy process to create a new garden bed, you may be turning more of your lawn into garden beds, giving you plenty of room to grow all of your beautiful and unique plants out there!