What do I put on the bottom of a raised garden bed? This question has been asked several times by gardeners with raised beds, I have decided to write a detailed article about things to put at the bottom of your raised garden bed.
Many gardeners opt for raised garden beds instead of planting directly on the ground, especially if the soil isn’t of the requisite quality. This comes with several advantages including minimizing or even eliminating the growth of weeds and a decrease in the labor required to grow crops.
When laying the groundwork in preparation for a raised vegetable garden bed, a niggling question for many newbies is what to put on the bottom of their raised garden bed. Choosing the right barrier between the ground and garden soil is crucial to the overall success of the raised garden.
The answer to that question is what we would be looking at in this post. By the end of the post, you’d know the right materials to line the bottom of your raised garden bed and the preferred option to use depending on your specific situation.
What Do I Put on the Bottom of a Raised Garden Bed?
While this post is primarily about what to use when lining the bottom of your raised garden bed, a critical yardstick must be in place first – the raised garden bed must be over 6 inches in depth for the plants to thrive.
This is basically because most garden plants need a soil depth (garden bed depth) north of 6 inches for adequate root development. Anything less doesn’t provide enough space for that. If soil depth is less than 6 inches, the expert recommendation is to put nothing.
With that out of the way, we can now look at what to shroud the ground with before laying out the soil the crops would grow on.
7 Great Materials to Put on the Bottom of a Raised Garden Bed
1. Landscape fabric
This is one of the best options for lining the bottom of an elevated garden bed especially if you don’t mind the cost. Made from recycled material, polyester, or linen, it comes with tiny holes over the surface making it permeable. Water drainage won’t be an issue.
The relatively high cost of getting it is usually offset by the fact the material is resistant to decomposition. Expect to use it for about a decade before needing a replacement.
Keep in mind that there is a huge difference between landscape fabric and landscape plastic. While you can also use landscape plastic for weeds control in gardens, the absence of holes makes them very unsuitable for this project. Remember, the holes are essential for drainage.
2. Hardware fabric/mesh
Also known as gopher or rat mesh, this is a very durable material that comes highly recommended to put on the base of a raised garden bed.
While this can’t keep weeds out of your raised garden, it would certainly prevent pesky garden pests like rodents from nibbling at plants after burrowing underneath the beds. This usually occurs when these pests can’t get at protected plants from above. The holes are too tiny for even the smallest pests to pass the wire mesh.
Stainless steel hardware fabrics are even more durable than landscape fabric. But since they are incapable of keeping out weeds, it’s best to use them in collaboration with other materials.
Some folks confuse garden hardware fabric with chicken wire. But they are two different things with chicken wires having bigger holes.
The very eco-friendly burlap is a cheaper alternative to landscape fabric. It comes with similar advantages including the fact that it is cheaper to get. It doesn’t last as long though, but you can squeeze out several years of good use from it.
Made from jute plants, burlaps are also great at letting water pass through them.
Though they take a while to decompose, the decomposition can be accelerated by frayed edges. Unfortunately, it doesn’t take much for the edges to start fraying. Exposure to the elements for some time or even cutting them to lay on the ground can set the decomposition process in motion.
Another issue to deal with is related to how easy the material unravels. When burlap is cut, the edges easily wear out making the material look messy and untidy.
When it comes to wood, you can use any type of wooden planks, wooden scraps, tree branches, logs, etc., to put on the bottom of a raised garden bed.
Wood is fairly durable, but expect it to decompose over time. The time frame for full decomposition is around a couple of years but that varies depending on the type and thickness of wood used.
Concerns have been raised about the effect of chemicals on the plants and soil when using pressure-treated wood. But research shows that the chemicals in pressure-treated woods have little to zero toxic effects on the plants. Certainly, there is no long term soil damage linked to deploying commercial wood underneath raised garden beds.
Laying leaves at the bottom of a raised garden bed is the first of three budget options at your disposal.
Leaves, like all the other options above, would keep weeds out of the garden bed for some time. The leaves would eventually decompose but that should take between 6 to 13 months. But decomposing leaves are generally good for the soil since the process adds lots of essential organic matter to the soil.
That said, you want the leaves to last as long as possible. The best option is to spread as much of the leaves as possible before dumping the garden soil on them. The more leaves packed in the bottom of the garden bed, the longer it would take to decompose fully.
6. Old newspapers/magazines
Old newspapers or magazines provide the cheapest and easiest solution. Installing them is just a matter of spreading the sheets across the ground until the whole surface is covered.
Then simply install the garden soil on the sheets of paper and you are good to go. The sheets of paper are very effective in keeping weeds out of your garden beds. One benefit of using this material relates to the cellulose composition of the papers. The organic cellulose breaks down over time adding more nutrients to the soil.
Concerns have been raised about the chemical impact of the ink on the soil and plants. But this shouldn’t be an issue because the ink is soy-based and have not toxic effect on plants or the soil.
But newspapers or magazine pages take far less time to break down or compost. This opens up the soil to the proliferation of weeds. Using several layers of paper is the best way to mitigate this problem. With more layers, it would take longer for the papers to decompose completely.
Cardboard is also another great, cheap, effective material to put at the bottom of a raised garden bed. Like newspapers, it shouldn’t be hard to source for them.
Cardboard also decomposes over time. But because they are thicker, you’d expect this process to take a bit longer compared to newspapers. The rate of decomposition, though, would depend on the thickness of the cardboard and environmental factors. Generally, decomposition takes between 4 – 6 months which is enough time to cultivate many garden crops to maturity.
If you want the best from cardboards in terms of longevity, look for the multilayered types. These resist decomposition a lot longer than the single-layered cardboards.
However, not all cardboard can be used for this purpose. Steer clear of cardboard with glossy and colorful prints like shoe boxes, beverage and cereal boxes, some electrical appliance boxes, etc. You don’t want the toxic ink on the cardboard getting into the soil after decomposition. This can be very harmful to the plants and the surrounding soil.
There you go! A list of seven (7) appropriate materials to put at the bottom of raised garden beds!