Cardboard Weed Barrier

Weeding is a chore I really don't enjoy!  But, my new-to-me home is near a lake so we all try to limit the use of chemicals in our yards.  Is my method of controlling weeds using cardboard in my garden beds hard?  NO!  It's actually easy.  Chemical-free weed control is environmentally responsible for many reasons.  

Getting rid of (or at the very least significantly reducing) weeds has allowed me to enjoy my gardens. I've been planting raised garden beds and also planting groundcover plants so they will take care of smothering out future weeds. Then I don't need to keep mulching those areas!

How to Keep Weeds Out of the Garden

Cardboard is a wonderful weed barrier if used the correct way. Compared to using landscape fabric, cardboard is much better for the health of your soil. It prevents weeds, especially weed seeds from germinating. It does decompose and will turn into organic matter to feed your soil nutrients. There is some maintenance which I'll review further down this post.

Cardboard under Mulch

When I moved into my home 6 years ago, I had a plant called snow-on-the-mountain (Aegopodium podagraria 'Variegatum'). on one whole side of my house. Any gardener trying to eliminate this knows the challenge of removing this weed. It's also called bishop's weed, goutweed and ground elder. It's nasty and hard to get rid of.

I've been a supporter of the use of cardboard for weed control for years!

First you put a layer of cardboard down. Then soak it. The final step is a thick layer of wood chips and/or mulch. I've been asked quite a few questions about this process. Hopefully I cover most things people want to know below.

How does cardboard prevent weeds?

• It prevents seeds from germinating because the cardboard blocks sunlight.
• Plants that self seed usually can't germinate in mulch covering cardboard.
• Having cardboard a more impermiable layer for weeds than just mulch alone.

Steps to putting down cardboard and mulch

Step 1

Give my garden bed a good weeding and try to remove as many weeds as possible. I don't try to get every bit but as much as I can. I usually hand weed. Depending on the weed and your tolerance level to chemicals, some people use a chemical weed killer to kill the weeds rather than hand-pulling them.

Step 2
I put down a layer of cardboard shaped to the bed. Make sure to give the plants a big enough space in the cardboard so the water gets to them easily. I ensure the cardboard layer is at least 6 inches away from the plant on all sides. This allows water to get to the roots of the plant. Although the cardboard isn't in direct contact with the plants, this will significantly reduce weeds in flower beds.

Make sure the cardboard is overlapping a few inches so that the weeds don't grow between the cardboard pieces.

Step 3
My landscaper gave me a great tip. He said to water the cardboard until it's soaked a couple of times. Then put the mulch on top. When the cardboard is soaked, with some weight on it, the cardboard will kind of glue together.

Step 4
A thick layer of mulch helps hide the cardboard, also helps prevent weeds, and keep your gardens neat. I also believe the mulch layer keeps the roots of the plants cooler in the hot summer. And, it definitely helps retain moisture.

Is chemical-free weed control expensive?

This year, my weed control in my garden beds was very inexpensive.   The materials were free and I didn't count my time or that of my family (and I know that time has value).  Cardboard is such an inexpensive way to control and reduce weeds! I have a lot of garden beds that I'm starting (or maybe I should say saving?).   The only cost for me was my time and effort to do this.

This cardboard method also significantly eliminates (for me) the need for Preen weed control.   I have used Preen in the past to reduce weeds from germinating. But, I no longer use it!   That's a win for my wallet and the environment.

Wait, how did you get free mulch?

I have huge trees in my backyard.  But, they were actually dangerous because they were dropping big branches (too close to me when I was cutting the lawn).  I had an arborist come and take down the dead, damaged branches and lighten the weight on some of the branches.

It was interesting and fun to watch.  I'd encourage you to take a peek at my post called Why to hire an Arborist for more info. about what they did and how they did it.    They chipped up everything they took down.  I asked if they could just leave all the chipped up wood for me and they did.   It was a ton of free mulch for me to use.

And two years later, I had a large dying maple removed. Lots more free mulch! The arborist companies are often very happy to leave the wood chips behind. It saves them from having to dispose of them.

Weed control around trees

Years ago, I had a bunch of huge fir trees and there was no way I could get under them to pull the weeds.   I used the same method there!

I have some beautiful trees in my back yard. I love the look and the privacy they offer. But, the weeds!!

The trees are huge! You can imagine how hard it is to reach in and pull the weeds/grasses out. I usually did it a couple of times in the summer and I either roasted wearing a jean jacket or totally scratch up my arms. I just hate seeing the grasses/weeds under the trees.

Killing Weeds with Cardboard

I've used cardboard for years in one of my flower gardens to prevent weeds. I decided to use cardboard around the tree base to prevent the weeds from growing under the trees. Since I couldn't weed underneath the trees, the cardboard was also used to smother and kill the weeds and grass.

I split a cardboard box in half and then cut out sections for the trunk.

Then I pushed the cardboard under the tree branches.

Just an fyi, I needed to use three cardboard sections to surround the tree base fully. Two just wasn't enough and I wanted to be sure the cardboard overlapped and that I was totally covering the area where the grass/weeds were growing.

What time of year can you put down cardboard for weed control?

ANYTIME!  I initially put down a ton of cardboard in the spring and mulched it.   I find it easier because the plants (shrubs and established perennials) haven't grown large yet, so working around them is easier.

I also like doing this in the fall. When summer is ending, retailers sometimes have big sales on mulch!  So, at the very least I'm getting the cardboard down and with a thin layer of mulch so the weeds are under control this year and won't pop up in the spring! What a great way to get ahead of your spring gardening!!!

Other gardening posts

I've been working hard on my yard! It's a work in progress but it gets better every year! I invite you to look at some of my other gardening posts.

FREE BONUS MATERIAL BELOW

Background to why I had such a weed issues.

A tiny bit of history.  My house basement was flooding after I bought the house (it was kind of an as-is fixer upper).  I had numerous people try to diagnose the problem.  They all came up with the same thing.  The landscaping around the house needed to be removed and the dirt around the house needed to be regraded so the rainwater would flow away from the house, rather than towards the house - and into my basement.

Do you think maybe (just maybe) the landscaping I inherited was just a tiny bit overgrown?  At this point, I had been using ropes to hold up/back all the crazy hydrangeas!  They were so overgrown they were covering part of the driveway!

After most of the landscaping was removed.  If you want to see more about the work and how it was done, take a look at my post What to Do with Dried Hydrangeas.  I share a little more about what happened to my yard and how I saved a bunch of my hydrangeas.

And, just to confirm, the picture above and below are of the same corner of my house.

And once I had my bare ground covered, I put a thick layer of shredded mulch/wood chips that was a minimum of three inches.  My original goal was to use this free mulch (which isn't very pretty) and then put some pretty colored mulch on top.

So back to my cardboard and free mulch.   Cover as much of your bed with cardboard as you can and add the mulch on top.  It truly smothers the weeds and prevents more from growing.

It totally cleaned up the look in my beds and got those weeds under control.   I ended up doing all the mulch myself.  Many of my new neighbors stopped by to say hello and tell me that the yard looked great!  It looked so much cleaner.  And, when some weeds do peek through, like the tiny one behind this planter, they are easy to pull out!

Yes, it was so much more of a clean look and the weeds cannot grow through the cardboard and mulch layer.  Now, I'll admit that they poke up by the edges of the cardboard, but that's not an issue and they are easy to pull!

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