The bottom of a raised garden bed is the foundation of the entire bed, get the foundation wrong and the plants growing in the garden bed will definitely struggle. Ideally, a raised garden bed should contain plenty of organic matter which breaks down over a period of time, but it is also important that it contains at least some brown composting materials that break down slowly and are jam-packed with nutrients.
When planning your raised garden bed you have to think about how long you want the raised garden bed to be productive. If you want a productive garden bed that lasts for several years then you should definitely use wood logs as the bottom layer. On the other hand, if you are planning to make a new raised garden bed in the near future then you should mostly use organic matter that decomposes quickly, like hay, compost, grass clippings, and so on.
In addition to this, you also have to consider what kind of problems you have in your garden and protect your raised garden from them. If you have a serious weed problem then you can use plastic fabric as the bottom layer, if you have gophers in your area then use gopher wire as the base of the raised garden bed. You should also mulch your raised garden bed with wood chips or ground cover plants, for more information check out my recent article Ground Cover Instead Of Mulch ( Top 9 Pros & Cons ).
What To Put On Bottom Of Raised Garden Bed
In my personal experience as a gardener, I have found that adding a layer of materials at the bottom of a raised garden bed can be beneficial. One option is to place a layer of landscape fabric or weed barrier to prevent weeds from growing up into the bed. This helps to minimize competition for nutrients and ensures that the plants in the bed receive optimal resources. Additionally, I like to add a layer of cardboard or newspaper on top of the weed barrier to further suppress weed growth.
The cardboard or newspaper acts as a natural biodegradable barrier, preventing grass and weeds from penetrating the bed while allowing water to pass through. This method not only helps to create a weed-free environment but also promotes healthy root development by allowing proper drainage. It’s important to note that adding drainage materials like rocks or gravel at the bottom of the bed is not necessary and can impede drainage.
Logs
If you want a long-lasting raised garden bed then you should use logs as the bottom layer. This method is also knowns as Hugelkultur and it has been used in Germany and in Eastern Europe for hundreds of years already with extremely good results. Place on the bottom of the raised bed several logs, the bigger the better, these logs will break down and feed your plants. Generally speaking, it takes around 4-8 years until the logs break down completely and the raised garden bed should be remade. One of the main reasons why people use raised garden beds is to protect their plants from snails, although snails are actually beneficial for the garden, for more information check out my recent article Benefits Of Snails In The Garden ( Top 7 Pros ).
Cardboard
Cardboard is an excellent weed suppressor, and this is an extremely good bottom layer for raised garden beds especially if you are building the raised garden bed directly on top of some vegetation. Cardboard decomposes relatively fast, but until it does it will retain moisture in the soil and smother out most weeds. My suggestion is to place down a layer of cardboard and place right on top of it a couple of logs as well, and this way the bottom layer of the raised garden bed will last you for several years. If you want to know how long does mulch lasts then check out my recent article How Long Does Mulch Last ( Months Or Years? ).
Soil
Most people choose to place soil on the bottom of the raised bed, as this is the cheapest alternative and works fairly well. Although you really need to consider what kind of soil you actually use, if you want to use your own soil then make sure that it doesn’t contain a lot of clay. Clay soil as the bottom layer of a raised garden bed will eventually compact and most plants will not be able to push their roots through compacted clay soil.
Landscape Fabric
Landscape fabric can be an excellent bottom layer for raised garden beds, although its main function will be to suppress weeds. If you are building your raised garden bed directly on top of vegetation, then you can use landscape fabric to smother out weeds. Ideally, you should have a relatively tall raised garden bed for using landscape fabric as it doesn’t let water drain out at the bottom which can be problematic for some plants.
Grass Clippings
Grass clippings are not only an excellent mulch but are also an extremely good bottom layer for raised garden beds. Grass clippings tend to break down relatively fast, and the released nutrients will be able to feed your plants. If you have a relatively short raised garden bed then grass clippings should be placed on the bottom, especially as they break down so fast. On the other hand, if you have a relatively tall raised garden bed then you will need to constantly mulch the raised garden bed as the grass clippings decompose they will sink in the topsoil.
Leaves
A bottom layer of leaves can work wonders for your raised garden bed, just make sure to use plenty of leaves. If you are building your raised garden bed in the fall, then place as many leaves in the raised garden. Leaves break down relatively quickly, and once spring comes you can place on top of them, compost, mulch, or soil. This way the soil in the garden bed will be jam-packed with nutrients.
Wood Chips
Wood chips on the bottom of the raised garden bed not only feed your plants but will also help with aerating the soil. The bad news is that you will need a relatively thick layer of wood chips if you want to use them as the base of your raised garden bed. Although wood chips at the bottom of the raised garden bed are good but my personal recommendation is to place wood logs at the bottom and use the wood chips as mulch for the raised bed.
Straw Or Hay
Straw or hay can be used on the bottom of the raised garden bed, they break down relatively fast, retain plenty of moisture and smother weeds out. The main problem with straw or hay as the base of a raised garden bed is that they decompose extremely fast, this means that the bottom layer of the raised garden will simply vanish in a year or two at most. You can get around this problem by mulching the raised garden bed once you see the soil start sinking in.
Stones
In areas where the humidity is relatively high and your plants often rot, you should use stones or rocks as the base of your raised garden beds. Their main purpose will be to help with drainage, although they are also good at smothering weeds out if they are spaced out tightly. Under no circumstances use rocks or stones as mulch for drainage in your raised garden bed, as with time the weight of these will compact the soil and most plants will not be able to push their roots through the compacted soil.
Newspaper
Newspaper works similarly to cardboard when placed into the soil, although with one major difference which is that newspaper is almost waterproof, and this is the same reason why you should not flush it down the toilet. On the other hand, newspaper can be used as a base layer for your raised garden beds and its main function will be to retain water and to smother weeds out. Newspaper does break down after some time in the soil, although cardboard contains more nutrients than newspaper when it comes to feeding your plants.
Gopher Wire
If you have a problem with gophers in your area then you should place on the bottom of your raised beds some gopher wire. Consider this layer as a protection against the gophers, and place organic material or soil on top of the gopher wire. Just keep in mind that gopher wire will eventually rust away, so make sure to get the thickest gopher wire that you can find.
Compost
Compost can be used as the base of a raised garden bed, but only if the raised garden bed is relatively short. If you have a tall raised garden bed then the nutrients from the compost will not be available for the plants until the roots of the plants reach the compost. Ideally, you should make a thick layer of compost if you are using it on the bottom layer of the raised garden bed, as compost will sink in the soil once it has decomposed.
Key Takeaways
- You can put on the bottom of your raised garden bed organic material that smothers weeds, retains water, and feeds your plants. Organic materials like wood logs, grass clippings, hay, leaves, and even cardboard are excellent for the bottom of your raised garden bed. On the other hand, if your main concern is with weeds, and pests then you can use landscaping fabric and gopher wire to protect the bottom of your raised garden bed.
- Placing a layer of landscape fabric or cardboard at the bottom of a raised garden bed can help suppress weed growth. These materials act as a barrier, preventing weeds from growing up through the soil and invading your garden.
- Installing a layer of wire mesh or hardware cloth at the bottom of the raised bed can help deter burrowing pests, such as moles or gophers, from accessing your garden. This provides an additional layer of protection for the plant roots.