Five tips for a successful DIY cardboard weed barrier
This is how our garden looked when we moved in.
A HUGE sea of weeds.
Yikes. But I was determined to have a garden.
After learning how tilling harms soil, I set out to cultivate a no-till garden… by weeding by hand.
Days of work and sore body later I thought, there HAS to be a better way.
Cue my happy discovery about a biodegradable and free weed barrier–cardboard.
In a quick nutshell here’s the logic behind a biodegradable weed barrier: weeds love light, and tilling the soil exposes tons of seeds to light. Block the light and you block the weed growth. Cardboard is awesome because it will biodegrade and not hurt earthworms like fabric barriers.
So the big question: Would I do it again?
My answer: Absolutely YES! **If done with a few key tips I learned.**
Your urban garden is totally possible too!
Cardboard Barrier Tips
Tip #1: Weed wack first
Part of our garden was weeded by hand, some covered by a tarp for a few months to kill weeds, some had the top two inches flipped over, and part was weed wacked then covered with 6 inches of mulch. They all worked with varying levels of success, but if I were to do it again the most effective would be to 1. hand pick the most pernicious weeds like dandelions, 2. weed wack, then 3. flip the top two inches of soil over with a shovel to disrupt the roots. Unlike a full till, this will just help to dry out weed roots in the sun.
Tip #2: Collect large pieces of cardboard for maximum coverage
While smaller boxes still work, any crack in coverage is an opportunity for weeds to break through. We started with small boxes and then discovered the cardboard goldmine: furniture stores. They throw away huge pieces of cardboard all the time, often without a lot of ink or a ton of tape to remove. The only downside is you’ll probably need a truck to transport the large pieces. But so worth it. We got a load that helped finish our cardboard weed barrier and had enough left to build a castle for the kids. See how it turned out in our princess and knight birthday party.
Tip #3: Wait to put down the cardboard
We got so excited to cover the ground with cardboard that we didn’t consider the wind. There was a particular windy day that blew many of our boxes into the neighbor’s yard. Ooops. So wait to put down your cardboard until you have your next layer ready to weigh it down.
Update: if you live in a dry climate cardboard may not be the best option. Mine still hasn’t broken down, but it is helpful to supress weeds. The alternative is to use a deep mulch (at least 6 inches deep) to suppress weeds.
Tip #4: Use edging
We have yet to implement this one due to budget constraints, but next year I definitely want to add edging to the garden. After we added woodchips on the path, and soil to the garden beds it looked so crisp and defined. The path is still there, but the wood chips often spread onto the cement and into the garden beds a bit. Garden edging will keep things nice and tidy.
Tip #5: Find free mulch
I used a mix of Back to Eden and lasagna gardening techniques to create fertile soil that will last. But sometimes the best permaculture gardening techniques don’t look pretty. Like grass clippings all over your garden bed. Anyway, buying dirt to cover some of the cardboard was probably the most costly part of installing the garden. It’s lack of weed seeds was worth it. But I’m glad we got free wood chips for the path! We found ChipDrop to be quite helpful. The loads dropped off are usually pretty large, so if you look in the network map you can often find people who have extra. Plus, you can check out the quality and avoid loads that have too many branches.
Another source of free wood chips is a local tree service. We needed a lot of wood chips, so when our neighbor cut down their huge sycamore tree we asked the tree service guys if they would dump some of the wood chips on our RV pad. They did it for free! But it was a HUGE pile. Like as tall as me and the whole length of the RV pad. And because we left it while on vacation it started decomposing in the middle. Great for creating soil, but not so great for inhaling while shoveling into a wheelbarrow. So just be sure this is what you want if you go this route.
Anyway, hope these tips helped. I’ve hardly had to weed AT ALL since our cardboard barrier install. The main challenge spots have been the edges along the sidewalk where the cardboard moved in a storm. I’m hoping that adding the edging next year will fix that.
Stay tunned for my garden update for next season. We’ll see how the cardboard barrier holds up over winter.
Happy gardening!
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