What Should You Put at the Bottom of a Raised Garden Bed?
What should you put at the bottom of a raised garden bed? You have several great options for putting underneath your raised beds — and some ideas that are unnecessary, or should even be completely avoided. Set your garden up right and in the long run you will be grateful you did with this step-by-step guide.
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In This Article
- What you should put at the bottom of a raised bed garden.
- What you should not be putting underneath your raised beds.
- What to put in the bottom of short raised beds (6-inches.)
- What to put in the bottom of very tall (30-inches or more) raised beds to cut down on soil and compost needed if budget is a concern
The best option — and the simplest and best materials to put at the bottom of a raised garden bed — is a layer of cardboard (ideally two layers) followed by wood chips and hardware cloth to deter critters, followed by more wood chips and/or leaves on top of that if the height of your raised beds allows it. This combination will give you the best results and suppress weed growth, deter tunnelling animals — all while not interfering with drainage or plant roots.
Do not use shiny cardboard as it has plastics in it that will stay in your environment forever.
Cardboard and wood chips are an easy or free option that is accessible to most people.
You can get dump trucks of free wood chips delivered to your home (more on that below) and stores are full of cardboard you can collect. In the autumn months, when homeowners bag up piles of leaves and you can collect these from the curbs as you go by.
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What Can I Put at the Bottom of a Raised Garden Bed to Prevent Weeds?
You have multiple options.
Some are free or cheap and others are less so.
You need to start with a weed suppressing layer at the bottom of your raised bed garden no matter what height your raised beds are.
If your raised beds are on concrete or gravel, then weed suppression is obviously not a major concern, but the cost of filling the beds — especially very tall ones — might be an issue.
We will discuss easy and cheap ways to fill the bottoms of very tall raised beds below your soil level if budget is a concern.
If you have 6-inch raised beds it is best that you stick with simple weed suppressing materials, like cardboard (two layers is best) with a thinner layer of wood chips, followed by your soil.
If you have 12 to 20-inch (ish) raised beds, you can apply a thicker layer of wood chips and even add more organic material like grass clippings, leaves, and small sticks.
If you have tall raised beds that are at least 30-inches or more — you can add sticks and whole logs to fill about one-third of your raised beds on top of the weed suppressing layer of cardboard, but below your soil layer.
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What Should You Put at the Bottom of a Raised Garden Bed?
All of the things that should go in the bottom of raised beds, followed by the things that should not.
Cardboard
A good idea is to start with a thick layer of cardboard which takes 4-6 month to break down and in that time it will suppress weeds and germination of dormant weed seeds.
In colder climates, that layer of cardboard might still be kicking around your next gardening season.
Two layers is best, but you can do one layer, or even as many as 3 layers.
Avoid plastic coated cardboard, it will be easy to tell by the shiny gloss, and try to remove all of the tape and staples you can.
A great option for cardboard, is to collect it from big box stores like Costco and various furniture and appliance stores. It helps to call ahead and speak to a manager who can even set some aside for you.
Layers of newspaper are also good. Avoid glossy print to avoid toxic chemicals, plastics, and other things you don’t want in your environment.
And whole leaves are fantastic here too.
Wood Chips
A layer of wood chips that is at least 2-inches deep, but preferably 4 inches is ideal.
If your raised beds are taller than 15 inches, you can add even more.
Yes, wood chips will tie up nitrogen as they break down and compost, but this will not affect your plants in any way unless maybe your soil is very poor and dead.
You should be layering compost on top after filling your raised beds anyways.
Just make sure its untreated wood.
Wood chips can be gotten for free from various USA and Canadian sources and those links will take you to a company that connects gardeners with arborists.
Arborists would much rather dump a load of wood chips onto your property rather than pay the dump fees to dispose of all the wood they have through the season.
You cannot control or predict the timing or amount of wood delivered, so just get on the list — our massive pile arrived last year and we will be using it in the garden just now in the spring.
If there is too much, just put the word out for other gardeners and they will come take what they need when you’re done.
But it doesn’t hurt to have spare wood laying around either, if you have chickens or other birds, for example, you can use wood chips in their coops and houses.
We use wood chips in our coops alongside chopped straw and other organic materials with the deep litter system.
More From The Blog
Importance Of Hardware Cloth
One other thing I highly suggest you add to the bottom of your bed — 1/2 inch or 1/4 inch hardware fabric.
This should go directly beneath the raised beds and on top of the cardboard.
This will prevent voles, who can easily tunnel through your soft, rich soil, from eating your garden root vegetables.
And this step is easier done at the beginning then afterwards when the raised beds are full of soil and your carrot crop is mysteriously missing.
Grow Guides
Weed Barrier Cloth
Some people opt to skip the cardboard and wood chips and use landscape cloth or a weed barrier cloth or landscaping cloth.
But they’re generally made out of plastics and I’m not keen on polluting with more microplastics as the barrier eventually begins to degrade and breakdown.
You can use something like undyed linen, cotton, or wool though, as long as it allows for proper drainage.
There are natural and biodegradable sources of weed barrier cloth.
Adding Leaves to the Bottom of a Raised Garden Bed
In the autumn months, the suburbs are full of home owners raking up leaves and leaving them on the curb for pickup.
Outside of the fact that destroying all of these leaves is actively contributing to the extermination of countless native species of insects and beneficial pollinators — those bagged leaves are worth their weight in gold in your garden.
Leaves can be shredded and composted in your bin along with other greens and browns. Or you can make leaf mold, a sustainable alternative to peat moss and coconut coir that provides some nutrients to the soil.
Leaves can be left whole and used in the bottom of raised beds in lieu of cardboard as a weed suppression layer or in lieu of wood chips too.
The brown bags they come in can be used like cardboard too, or simply composted.
Leaves are also a wonderful mulch to protect your soil and can be used that way as well as on top of your soil in raised beds.
See my article on how to shred leaves for mulch for more information.
Consider also leaving some wild areas in your property and leaving the leaves alone so that the insects, fireflies, and pollinators can have a chance. Consider getting the book Nature’s Best Hope: A New Approach To Conservation That Starts in Your Yard.
Related
Hugelkultur Method: Adding Sticks & Logs
If you’re in any way involved in anything permaculture — you’ve heard the term hugelkultur thrown around.
Briefly, hugelkultur, has been practiced for centuries and is a method of raised bed gardening that involves making raised garden beds filled with rotten wood logs, sticks, and other plant debris followed by compost and/or soil.
In a tall raised bed that is 30-inches or taller — you can absolutely fill the bottom one-third of your beds with this type of material, but it should still be on top of some cardboard at least, and wood chips are still a nice addition.
This benefits your soil (potentially) in ways that are beyond the scope of this article while making it much cheaper to fill those enormous beds that can sometimes require 2 yards of soil or more to fill.
Sheep Fleece & Wool
Our Icelandic sheep give us beautiful next-to-skin soft wool each fall when we shear them.
However, their spring fleeces also need to be sheared and they are generally coarser and so full of vegetable matter that most of the fleece is only suited for yarn to make carpets, dryer balls — or composting.
But you can also use your fleece at the bottom of your raised bed gardens instead of wood chips or leaves — and you can use it on top as a mulch too.
Commercial sheep operations that breed for meat will often have tons of wool that can be given away — start calling farms, it’s wonderful stuff.
What Should You NOT Put at the Bottom of a Raised Garden Bed?
There are some good and great materials to put in the bottom of the raised beds — here are two you should not use.
Don’t Use Plastic or Trash Bags at the Bottom of Your Raised Beds
You absolutely do not want to line your raised garden beds with plastic or plastic trash bags at the bottom.
This will trap water, prevent adequate drainage, potentially cause a host of root issues and diseases.
Woven plastics designed for weed control are a different matter, we’re talking about plastic sheets, tarps, and trash bags — don’t do it.
Don’t Use Gravel in the Bottom of a Raised Bed
If your raised bed garden is on a gravel platform or prepared site — that is perfectly fine. That is not what I’m talking about.
I’m suggesting that you do not fill the bottom of your raised beds with gravel thinking that the gravel will aid with drainage — it won’t.
One of the benefits of raised bed gardens is the improved drainage from the beds themselves, you don’t need to worry about drainage.
And if you fill up the beds with too much gravel, your plant roots may end up sitting in the wet, water logged gravel instead of draining away as you are hoping.
If your beds are shorter this is especially problematic. Stick to organic matter, even if your beds are sitting on something harder.
Should I Put Sand in the Bottom of my Raised Garden Bed?
There is no need and no benefit of adding sand into the bottom of your raised garden bed. If you have beds that are shorter than 20-inches — you should absolutely not add the sand. You don’t need sand for good drainage, the raised bed does that already.
Related
Adding Nothing — Do You Need To put Anything In The Bottom Of A Raised Bed?
The reason we line raised garden beds is to make our lives earlier.
Lining garden beds suppresses and kills weeds before they can germinate and multiply. They make the task of weeding easier and easier as the seasons go on (provided our soil and compost isn’t full of weeds) and something like hardware cloth can prevent the devastation of finding an entire root crop gone, eaten by underground animals.
You do not have to do any of this and many people choose to do nothing.
Weigh the pros and cons and do the best you can — but don’t let this deter you from starting your garden.
Don’t Forget To Mulch!
A brief but important reminder — now that you have the bottom layer of your raised beds figured out — don’t forget the TOP of the soil!
Once you’ve laid down that beautiful, expensive, soil and compost — MULCH!
Mulching helps avoid he problem of soil erosion, soil nutrient loss, and other bad things, it also retains water.
For all the information you need on mulching in your garden, check out my guide Benefits Of Mulch In Your Garden {Ultimate Guide To Mulching} for all the best resources and knowledge.
Related
How I Fill the Bottom of My Raised Garden Beds (Step-By-Step With Photos)
Instructions
- Add two layers of overlapping cardboard over the area where your raised bed garden will be situated. The cardboard layer is the first step to combat and suppress grass, weeds, and seed germination from unwanted plants. The cardboard will compost and break down slowly, taking 4 to 6 months — or longer in colder climates.
- Add a thick layer of wood chips. We added about 6 inches total of wood chips. They will break down very slowly and create another layer of weed suppression.
- Place your raised beds in the location you want them to be.
- Measure the the hardware cloth (we used an angle grinder with a thin steel blade, also called a cutting wheel) so that you will have about 4 inches (or more) sticking out from each side of your raised bed. This may require two pieces overlapping one another.
- Place the hardware cloth underneath the raised beds.
- Check the positioning of the beds — once they are filled with soil, it will be very difficult to move them.
- The hardware cloth will prop the beds up above the wood chip layer and will help you to make the beds even.
- Now you have several options depending on the height of your bed.
- The first option, and it applies to all heights, is that you can go ahead and fill your beds with your choice of soil and organic matter.
- If your bed is lower than 12-inches high, you should not add anything on top of the hardware cloth.
- If your bed is between 12-inches high, you can add an inch or two of wood chips.
- If your bed is 15-20-inches high, you can add up to 4 inches of woodchips on top of the hardware cloth.
- If your bed is 30 inches or higher you can fill the bottom one-third with logs, sticks, wood chips and other organic mater.
- Fill your raised beds with soil and then mulch the top to protect the bare soil.
- Cover the exposed hardware cloth on the sides of the raised beds with shovels of wood chips.
- Plant your raised beds away.
These are photos and step-by-step instructions from our spring 2023 raised bed garden build with our brand new Vegega metal raised beds!
(The coupon code PeasantsDaughter10 applied at checkout should get you 10% off or whatever is the best deal if sales are going on.)
I’ve been waiting to do this ever since we moved onto our new homestead in 2021 and this was an amazing and satisfying weekend.
(Follow The Peasant’s Daughter on Instagram if you want regular updates on the garden and homestead along with recipes on what to do with all that produce you’re growing.)
Should You Attach The Hardware Cloth To The Beds?
We opted not to attach the hardware cloth to our raised beds because they are made out of metal. I think the weight of the beds and the soil is more than enough to keep things in position.
If you have wood, you can staple the hardware cloth to the beds.
You can also drive long, thin metal spikes through the outsides of the hardware cloth into the ground beneath but you would need to find enough spikes at the right length and that can start adding up.
Final Thoughts
What should you put at the bottom of raised bed gardens? Several layers of cardboard followed by wood chips and hardware cloth. Depending on the height of your raised beds, you can then add more wood chips too. This combination is easy and accessible and it will suppress weeds while preventing tunnelling critters from accessing your vegetable garden. There are alternatives to the cardboard and wood chips and we covered those options too.
