7 Useful Ways to Repurpose Cardboard in the Garden – It's Good for Mulching, Seed Starting, and Even Supporting Wildlife
Your garden will thank you for not throwing away cardboard
I don't know about you, but my household generates a lot of cardboard – from packaging, deliveries, and the general everyday rubbish we seem to accumulate. Rather than chucking it in the recycling bin, I always save it for my garden. Whenever I'm mulching, composting, or preparing a new raised bed, I head straight to my cardboard stash.
It's one of the easiest ways to have an eco-friendly garden because cardboard has so many helpful uses in the yard. It's great at suppressing weeds, you can use it as a 'brown' material in your compost bin (you can pick up plain cardboard from Walmart if your compost needs a top-up), and you can even make plant pots out of cardboard.
But this sustainable trick does come with a word of warning. You should avoid any treated cardboard, any with a glossy or painted finish, and pieces that have sticky labels or are heavily inked. These either won't break down or could leach harmful chemicals into your garden's soil. Here, garden experts share their favorite ways to repurpose cardboard in the garden.
1. Add Cardboard to Your Compost
If you make your own compost, you'll know the struggle (especially in spring and summer) of finding enough material to maintain the 3:1 brown-green ratio. With so many fresh trimmings and grass clippings making up the greens, there isn't so much woody brown material to source from the yard this season.
This is where cardboard comes in, offering the perfect brown material to top up your compost pile.
'Cardboard makes an excellent carbon source for composting when it is clean and untreated. Shred plain brown corrugated cardboard into small pieces and mix it with nitrogen-rich materials like fruit and vegetable scraps or fresh grass clippings. It improves airflow and helps maintain the carbon-to-nitrogen balance needed for decomposition,' says Lauren Click, founder of Let's Go Compost.
But some cardboard finds itself on the list of things you should never compost, Lauren warns.
'Avoid composting cardboard with plastic windows, waterproof coatings, heavy inks, glitter, metallic finishes, or food packaging designed to resist grease or moisture.'
'Some food-contact packaging has historically contained PFAS ('forever chemicals'), and many coated papers and labels can introduce plastics or other contaminants into finished compost. When in doubt, leave it out,' she advises.
Lauren is the founder of Let's Go Compost, a 501(c)(3) nonprofit with a mission to make composting free and accessible throughout the United States. Lauren works both in the dirt (literally) with public schools and community gardens, while also remaining focused on the big picture - working with large organizations and policymakers to ensure composting accessibility and affordability are kept front of mind as infrastructure is developed.
2. Use Cardboard for Mulch
This has been one of the easiest and most effective ways I've used cardboard in my own garden – using cardboard as mulching sheets.
More specifically, I've placed sheets of cardboard on my beds to suppress weeds and stop grass growing through. A bonus is that as it breaks down, it adds carbon to the soil, feeding microbes and worms and improving soil structure.
'A lot of people use some type of landscape fabric or weed barrier product, but I don’t recommend it, especially in garden beds. It can work for a while, but then dirt and old mulch just build up on it or through it,' says Tyler Mainka.
'Weeds root right into the fabric and get nearly impossible to pull. But the main issue is that the fabric will start blocking water from flowing through it over time and break into small pieces of plastic eventually. Cardboard doesn't last forever, but that's the point. It breaks down, adds some plant matter to the soil and is usually free.'
He adds: 'We cut down tall weeds first and remove any seed heads; after that we wet the ground and lay the cardboard down. Put it down in a formation where it's covering all the grass and overlapping 3-4" at the edges of each piece (gaps will allow pockets for weeds to grow through).
'Water it again, then cover it right away with 3-4" of bark mulch (like this brown mulch from Lowe's) or wood chips. This keeps the cardboard from blowing away and helps block weeds,' Tyler advises.
You can actually purchase cardboard sheets from Amazon, designed for mulching in this way. Take care not to place cardboard directly against the base of plants, as it can lock in excessive moisture and limit airflow, causing fungal diseases and rot.
'Don't forget to remove all packing tape, staples, plastic shipping labels, and any glossy or waxed coatings,' Lauren Click adds. This staple remover tool from Amazon might be handy.
Tyler Mainka is the President of Best Bark Mulch, a bulk mulch delivery, installation, and landscaping company serving Waukesha & Milwaukee County, Wisconsin. The company also operates a wood-waste recycling yard, taking in tree waste, wood chips, and old mulch that would otherwise be discarded and grinding it into fresh mulch for delivery and installation.
3. Make Fun Plant Pots
If you want to be a little more creative with your leftover cardboard, use it to make DIY cardboard plant pots. It's a fun way to repurpose it while creating plastic-free pots for your plants.
This is best used for annuals, seedlings, or plants you want to have on show in drier months (cardboard pots being rained on excessively won't maintain their structural integrity for very long).
In fact, you can also use a cardboard plant pot as an alternative to plantable seedling pots (like these from Burpee), so you can avoid transplant shock for your most fragile plants.
Cardboard toilet roll tubes are perfect for this, as they're bottomless and will allow roots to easily find their way into the ground.
The reason cardboard works well as a material for plant pots is because it's breathable and will allow airflow to roots.
Just remember this isn't a permanent solution for your plants, but it is an easy, non-toxic gardening swap to make your own seed trays or display your favorite seasonal annuals.
4. Use It as a Potting Mat
Another way I regularly repurpose cardboard in the garden is by using it as a potting mat to keep my patio tidy when potting up containers and even houseplants.
Just like this IKEA potting mat, you can use a cardboard sheet as your work surface, catching any wayward compost so it doesn't cause a big clean-up job.
This is a good solution for the indoor garden, too, keeping your living room floor clean when working with houseplants.
The best bit is, you can reuse it over and over again.
To take it one step further, I gently bend the edges of the cardboard sheet upwards to create a lip. Not only does this keep the compost contained, but it also makes it easy to pour leftover soil back into the compost bag afterwards, saving on wasted resources.
5. Create a Bug Hotel
If you want to make a bug hotel, recycled cardboard is one of the best materials to use.
You can use a cardboard box to house all the different elements of your bug hotel (like in the photo above), as well as use it to form the structure.
Alternatively, if you have thinner cardboard to work with, cut long pieces and roll them into small tubes. You can then use them to fill a waterproof container (like this plastic food box from Walmart) to create the ultimate haven for beneficial insects, with lots of nooks for nesting and shelter.
Even if you have an existing mason bee house (like this beautiful hexagonal wooden one from Amazon), these DIY cardboard tubes can be used to refresh it.
6. Make a No-Dig Bed
Cardboard is a crucial material in no-dig gardening and setting up a no-dig garden bed.
Like using cardboard as a mulching sheet, you lay it down on bare ground to temporarily suppress weeds and grass. You should thoroughly water it so it then starts to break down. You then add a thick layer (4-6") of compost on top.
Over time, this creates a planting bed without having disturbed the soil beneath, maintaining (and even improving) healthy soil structure. Though you can often plant into it in the first year, if your compost level is sufficient.
Just watch out for no-dig gardening mistakes that may set your efforts back.
I was fortunate enough to spend a day at the homestead of no-dig pioneer Charles Dowding – read his top tips for composting and no-dig.
7. Use It to Protect Tree Trunks
Another clever way to repurpose cardboard in the garden is by using it for winter protection. More specifically, you can use it to guard tree trunks, protecting them from pests and damage.
In winter especially, tree trunks are susceptible to wildlife damage, including mice, voles, rabbits, and deer, which chew on bark when other food sources are extremely scarce.
Likewise, sunscald can happen, where the bark and cambium tissue die from rapid winter temperature shifts on cold, sunny days.
You can use a long, wide cardboard box to fashion a temporary tree guard that creates a physical barrier. It works much the same as the tree guards you can purchase on Amazon.
However, be aware that cardboard retains moisture and, if consistently wet, may attract pests. For this reason, it shouldn't sit directly up against the tree bark and should be replaced when it becomes soggy and warps.
Our guide to protecting trees from winter weather has more insight you may find useful.
What to Shop
These Felco F2 pruning shears are ideal for everyday use in the garden. They have replaceable parts to last for years of gardening.
This ceramic floral plant pot has a vintage feel. It has drainage holes to aid moisture management.
A soil moisture meter is good to have to hand, to quickly check your plants' moisture level and identify whether they need watering.
Cardboard isn't the only thing you can repurpose in the garden. You can also reuse old planters to make beautiful garden features and even to aid pest control. Or, reuse old pavers to add characterful details to your yard.
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