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.  I have written about the many 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.

Using 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.

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). This is based on me building many flowerbeds over the years.

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.

What kind of cardboard or newspaper should I use?

Use plain brown, uncoated cardboard, and it is ok if it has black ink on it.  Do not use glossy or coated cardboard, or any cardboard with colored ink as it contains heavy metals.  For newspaper, it must be non-glossy and black and white.  If a newspaper sheet has any color on it, it will contain heavy metals.

Now, if you never intend to eat anything growing in the garden you are constructing, as in it is a flower bed only, then using colored newspaper or plain cardboard with ink is probably ok. The amount of heavy metals added by a single application of newspaper or cardboard with these colored inks will be very small. Coated or glossy newspaper or cardboard though should be avoided, as it will take much longer to break down, and may contain more amounts of heavy metals.

Related==>If you are interested in learning about the possible risks/pollutants of using cardboard/newspaper, see our detailed guide.

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

1 – 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.

2 – Lay down news paper or cardboard over the area you want to kill/smother. 

If using newspaper, apply at least 10 sheet thickness.

3- 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.

Here is a Short Video we made on the entire process – Check it out!

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Want to see some other ways to remove grass?  Check out our guide on 5-ways to remove grass and start a garden.