Cardboard Weed Barrier: Pros, Cons, Set Up

landscaper showing a cardboard weed barrier in garden with a green wheelbarrow of top soil spilling out on top

As a gardener, I’m sure you’ve had moments when weeds seem oppressive.  Where do these weeds come from?  When you take the time to dig out and prep a new planting bed, put in topsoil and plant your flowers and bulbs only for weeds to poke up through it’s time to take action.  You’ve probably looked at the chemical options, but you’d rather avoid them.  When you are creating a new planting bed you may want to consider a cardboard weed barrier. These are a more eco-friendly way to solve the problem.

Does A Cardboard Weed Barrier Work?

Additionally, if you’re thinking of creating a new planting bed in an area which is currently lawn you may want to consider a cardboard weed barrier.  This is a great method when you don’t want to go through the process of digging out all the grass, only to put topsoil back in.  

It may sound like a strange idea, a cardboard weed barrier.  After all, cardboard is biodegradable, won’t the weeds just poke right through?  Eventually they will, yes.  However, for the first year or two, the cardboard will keep the weed seeds in the soil below from poking up through the newly planted topsoil.

How To Set Up A Cardboard Weed Barrier From Scratch

Luckily, a cardboard weed barrier is as easy to set up as cardboard is common. Here is a step by step tutorial on how to create a cardboard weed barrier in your garden.

Weed Barrier Prep Work

So how do you go about setting up your cardboard weed barrier?  First, you’ll want to choose where you’ll put your planting bed.  Whether you’ve dug out an area in preparation for the cardboard or you’re planning on putting the cardboard right on top of the grass, you’ll need to choose what area will be planted.  This will determine how much cardboard you will need.  

homeowner laying out a cardboard weed barrier for installation on green grass in a backyard

Next, find your cardboard supply.  Big boxes are best. In today’s Amazon world, that shouldn’t be too difficult. Although, if you don’t have the time to save your Amazon deliveries, you can always buy cardboard boxes for relatively cheap. You will need to do some preparation though before using the boxes in your garage.  First, you’ll want to remove any tape from the boxes.  Then you’ll want to peel off the shipping labels.  The idea here is to remove any adhesive from the boxes, and any plastic which will not biodegrade.

Cardboard Weed Barrier Set Up

Once you have your boxes broken down into flat cardboard, you are ready to start laying them out in your planting bed.  As you lay out the cardboard in the planting bed, you’ll want to overlap the seams between the cardboard by at least 6 inches, preferably 12 inches, especially if you’re going over top of grass.  

Once your cardboard is all laid out in the planting bed area, it’s time to cover them with topsoil.  You’ll want to add six plus inches of topsoil on top of the cardboard layer. This will give your plants a good bed to grow in.  Double check your plant type to confirm how deep the layer should be.  

After you’ve placed the topsoil on the cardboard weed barrier, it’s time to wet down the soil and get ready to plant.  Side note: you can customize this process in many ways. Some ideas include integrating irrigation, creating deeper spots for larger plants, and more.  

Cardboard Weed Barriers Summary

If you are creating a raised bed, a cardboard weed barrier is a great way to cover existing grass or weedy zones prior to filling your raised bed with soil.  It’s obvious but bears mentioning, the cardboard will eventually break down. Then, weeds will poke through to the surface.

However, you will save on having to pay someone to pull weeds. Additionally, by cutting off the weed growth from below for a season or two, you will reduce the unwanted growth for future seasons.   The best part?  You’re avoiding the use of toxic chemicals and your reusing cardboard boxes!