Kill grass & smother weeds with cardboard/newspaper

Using cardboard and newspaper to smother grass to make a flower bed is easy and effective. It isn’t too complicated, but you just need to make sure you use enough newspaper or the right kind of cardboard. We have written many times on different ways to remove grass, and this is just another tool in the arsenal for you to use! So, this simple guide will show you all that you need to do to expand your gardens by using newspaper or cardboard to smother and kill the grass. The cardboard/newspaper are a synthetic, yet biodegradable component to mulch and prevent weeds.

Use newspaper and cardboard as a weed barrier!

Did you know that using newspaper and cardboard can be just as effective as that weed-cloth / landscape fabric they sell? I’ve used a layer of cardboard or newspaper dozens of times to stop weeds from popping up in a new flower bed. Sometimes when we go to add mulch to existing flower beds/gardens, I find that they are a bit…ah-hem… weedy. Maybe they are looking a little overgrown. This is a great opportunity! You can put the newspaper cardboard down on top of the overgrown areas before adding mulch, and voila! You won’t have any of the old weeds poke through the new mulch. This will also prevent any other weed seeds from germinating on top of the existing mulch.

cardboard to smother weeds and kill grass — This was a neglected bed overrun with weeds. I weed-whacked them down, covered in cardboard, and applied mulch. No more weeds!

Should you use newspaper or cardboard?

I find that cardboard is the most effective at smothering grass, as it is just more robust and hard for a weed to poke through once moist. Newspaper will work too, but you need a whole lot of it (10 sheets thick). Sometimes I will just remove some of the grass with a shovel, then apply newspaper to prevent the big perennial weeds (like dandelions) from poking back through before I use mulch.

Illustrated Guide to kill/smother grass using Newspaper and Cardboard

Materials

Lots of newspaper. You will need enough newspaper to prevent perennial weeds from poking through it once it gets moist. I find that 10 sheets is sufficient. Make sure you use the regular newspaper (think of the New York Times), and not the shiny, plastic-like advertisements. The shiny/plastic advertisements take a really long time to break down, and might contain some other unwanted components.
Lots of cardboard. The kind that is brown/papery and has a corrugated cross-section seems to work the best. It is also biodegradable and will break down. I don’t use painted cardboard (like diaper or toy boxes), as it will take a lot longer to break down.
Mulch, or some big bricks or rocks to weigh everything down.

Illustrated Guide to Smother/Kill Grass with Cardboard

Identify the area you want to kill the grass. I find it best to make a small outline with a shovel, or trim up the perimeter a bit. Doing this helps me visualize what I want the final flower bed to look like.
Lay down news paper or cardboard over the area you want to kill/smother. If using newspaper, apply at least 10 sheet thickness.
Weigh down the cardboard / news paper. If making a vegetable garden, you may just need to use some rocks or bricks to kill the grass. If making a flower bed, then just apply your mulch! Now you have a biodegradable weed barrier that is just as effective as landscape fabric.