Gardening with raised beds can have several advantages over planting directly in ground. Some of the biggest benefits of using raised beds are that weeds are minimized and you have more control over the soil you wish to grow your plants in. However, starting raised beds often raises many questions. One of the most common questions is “What to put at the bottom of a raised bed”?
So what do you put at the bottom of a raised garden bed? Ideally, a barrier between your garden soil and the ground should be placed at the bottom of a raised garden bed to help prevent weeds from coming up. Common materials used for barriers include cardboard, newspaper, leaves and landscape fabric, but there are plenty of other options as well.
While there are countless different materials you can use as a barrier for your garden bed, they all have their pros and cons. In this article, we will be going over various materials gardeners put at the bottom of their raised beds along with their advantages and drawbacks so you can figure out which one works best for you.
Cheap and abundant, newspaper is a great option when it comes to choosing material to put at the bottom of your raised bed. Simply spread a few sheets of newspaper across the bottom of your garden bed, fill it up with soil and you’re all set! You now have a barrier to keep out weeds.
Even if you don’t get newspapers anymore, there are plenty of places you can get your hands on some for free. Public places such as the grocery stores, hotels, shops, recycling centers or the local library often have a bunch of old newspapers they need to get rid of. Contact one of them and they will likely have plenty of old newspapers they are willing to give out for free.
Newspaper is resistant to decomposition however, given enough time, it will eventually break down. While your barrier will be destroyed, it will release plenty of carbon into the soil. This is a good thing as carbon helps feed microbes living in the soil thus leading to a better, healthier garden soil.
As stated earlier, newspaper will eventually compost one way or another. However, one way you can slow down decomposition is to layer your newspaper. The more layers of newspaper you have, the more time it will take for the barrier to fully decompose.
One concern many people have over using newspaper is that it will harm the soil with chemicals and toxins because of the ink it’s covered in. However, newspaper ink is actually soy based, so it doesn’t do any harm to the soil or the plants growing in it.
Cardboard is another great material for putting at the bottom of a raised bed if you’re on a budget. Like newspaper, it is also very cheap and easy to get your hands on.
Cardboard will eventually decompose overtime however, since it is thicker and more durable than newspaper, its decomposition will take much more time. Cardboard usually takes around 4-6 months to decompose, but the type of cardboard you use however, greatly impacts its decomposition time.
Just like newspaper, there are also plenty of places that will give out cardboard for free. Retail stores, recycling centers and even websites like craigslist often have boxes people would be willing to hand out for free.
While you can use most any type of cardboard to line the bottom of your raised bed, you can expect the thicker, multilayered sheets of cardboard to work best. Their sturdy, corrugated structure allows them to resist decomposition far longer than flimsy single layered cardboard.
One type of cardboard you should avoid using however, is cardboard with glossy print on it. This includes but is not limited to things like cereal boxes, soda boxes and shoe boxes. The glossy ink on this type of cardboard can release chemicals and toxins into the soil when it decomposes. In turn, this will harm the surrounding soil and plants.
-More durable than newspaper
-Can’t use if it has glossy chemicals on it
If you’re willing to spend some money, landscape fabric is an extremely great material to put at the bottom of a raised bed.
One of the biggest advantages to using landscape fabric is that it is very durable and extremely resistant to decomposition. Landscape fabric will last for over 10 years before needing to be replaced. This makes it a great option in the long run.
In addition to lining the bottom of your raised bed with landscape fabric, you can also cover the top of the soil as well. Just be sure to cut out holes for your plants to grow through. By putting landscape fabric on both the bottom and the top of your raised bed, you will make it virtually impossible for weeds to come up.
Landscape fabric is also permeable so you won’t have to worry about it blocking out water. You can just water directly over the fabric and the water will pass through.
When shopping for landscape fabric, do not make the mistake of confusing it with landscape plastic as they are two entirely different materials. While landscape plastic is also great at keeping out weeds it provides absolutely no drainage as there are no holes or gaps for water to pass through unlike landscape fabric.
-Lasts several years
-Permeable and has good drainage
Burlap is a great alternative to landscape fabric. It won’t last quite as long as landscape fabric, but it will still be many years before it decomposes.
Burlap also is great at letting water pass through it thanks to the gaps between the threads. As a result, you will have better drainage in your raised bed if you use burlap.
Another perk of using burlap is that it is eco-friendly. Burlap is made from the fibers of jute plants. These plants take very little energy to grow, absorb several times more CO2 and produce much more oxygen than trees do. Talk about a green plant!
One drawback of using burlap however, is that the edges of it fray easily. When burlap is cut, teared or even just exposed to the elements for a period of time, the edges will wear out and unravel. This will make your burlap look messy and also accelerate its decomposition.
|-Takes a while to decompose|
-Cheaper than landscape fabric
-Doesn’t last as long as landscape fabric
-Prone to fraying
If any of the previous materials aren’t an option for you, putting leaves at the bottom of your raised bed can help keep out weeds for a period of time.
While it is pretty easy to fill up the bottom of a raised bed with leaves, they will most definitely decompose sooner or later. Leaves typically take around 6 to 12 months to decompose. On the bright, side those composted leaves will add lots of organic matter to your soil.
One way to combat the swift decomposition of leaves is to add as much of them as you can before you start adding the soil to your raised bed. When organic material such as leaves gets clumped and matted together, it can significantly slow decomposition. So the more leaves you pack into the bottom of your raised bed, the longer your barrier will last.
Most people have access to plenty of leaves in their yard, but if your property is lacking deciduous trees, websites such as craigslist and nextdoor.com may be able to connect you with people nearby who are willing to give you some for free.
-Adds nutrients to the soil
Stones, rocks or even pebbles are another good material if you’re running low on options. This option is a unique one because unlike the other options on this list, rocks will not decompose (at least not in your lifetime) making them a permanent barrier.
Despite them being nearly impossible to decompose, there are some drawbacks to using stones and rocks as a barrier for your raised bed that many would consider to be not worth it.
The first drawback to using rocks as a barrier is that it takes a lot of them to fully cover the bottom surface of your raised bed. While you will likely be able to find a few stones lying around your property, you probably won’t have enough to create a full barrier for the floor of your raised bed(s). As a result, you may have to reach out to other places to get more stones.
Even if you have enough stones for your raised bed, there are likely plenty of gaps between the stones that are big enough for weeds to grow through. One way you can combat this is to use smaller stones as smaller stones will result in smaller gaps.
Another drawback of using stones as a barrier is that it has poor drainage. Since water can’t really pass through rock, it leaves it with nowhere else to go. As a result, your soil will become soggy which will make it a breeding ground for various plant and fungal diseases.
|-Won’t decompose||-Takes a lot of them to cover the bottom of a raised bed|
-Weeds can still come up through the gaps
It’s always a great idea to lay down some hardware fabric at the bottom of your raised bed. Although hardware fabric isn’t very effective at keeping out weeds, its main function serves to keep out unwanted rodents and animals.
There are plenty of animals that want nothing more than to nibble on the vegetables and plants growing in raised beds. Because of this, gardeners will put up barriers with their raised beds to keep them out. However, once these pesky animals realize they can’t get to the plants from above, they will invade your garden by burrowing underneath the raised bed to get inside.
By placing a sheet of hardware fabric at the bottom of your raised bed, you can prevent animals from getting to your plants by burrowing under. The gaps between the wires of hardware fabric are too small for even the smallest of rodents to fit through and the metal wires the hardware fabric are composed of cannot be chewed through.
The only real drawback to hardware fabric is that it can’t really keep out weeds. This is an easy fix however, as hardware fabric can be used in conjunction with any of the other materials listed in this article.
|-Keeps out rodents and small animals|
-Can be used alongside other materials you put at the bottom of your raised bed
-Won’t keep out weeds
Whether it is wooden planks, logs, tree branches or even just wooden scraps, wood can be an effective barrier for the bottom of your raised garden bed.
Wood is pretty durable compared to many of the materials listed previously, but it does eventually decompose. Depending on the kind of wood you use and the condition that it is in, wood will usually take at least a couple years before it fully decomposes.
When it comes to using wood in raised garden beds, there is some concern about using pressure treated wood as it contains chemicals that could be potentially dangerous to the plants and vegetables. However, research from Pennsylvania State University has determined that the toxicity released from pressure treated wood is so low that it has virtually no effect on the plants.
|-Takes a long time to decompose||-Costs money|
In some cases, putting nothing at the bottom of your raised garden bed may be the best option for you. Although you won’t have a barrier to keep out weeds, putting nothing at the bottom of your raised bed is certainly the cheapest and requires no setup or hassle.
It’s entirely up to you whether you choose to put something or nothing at the bottom of your raised bed, but a good rule of thumb is if your raised bed is 6 inches or less in depth, then you don’t need a barrier. This is because the roots of the plants growing in your raised beds require space to develop and grow. Therefore, having a barrier in a shallow bed can inhibit their growth.
-Requires no setup
-Gives roots more room to grow
|-No barrier to keep out weeds|
By now you should have a few ideas as to what to put at the bottom of your raised garden bed. There are plenty of options to choose from all with their own perks and drawbacks, but it is up to you to determine which one is best for you. Regardless of which one you choose however, there will always be plenty of advantages of gardening in raised beds versus planting directly in ground.