Most gardeners love the idea of raised garden beds, especially since they protect the plants from weeds and pests and can be used to grow a number of different plants. In addition, they add an interesting look to the landscape and generally make gardening easier.
Raised garden beds can be made using materials like fabric, untreated wood or wood composites, and even galvanized metal (with a liner). Avoid using toxic or bulky materials like, stones, recycled wood, metal, and cement. Consider the material’s longevity and price when choosing.
When we talk about raised beds, the image that pops up in most people’s minds is a big planter box made of wood. But is that the only option or are there other better materials you can opt for? And how can you decide which material to opt for? Let’s find out.
What’s the Best Material for Raised Garden Beds?
Some of the most common materials used for raised garden beds include the following:
- Wood, including both softwood and hardwood, is perhaps the best option.
- Concrete or cinder blocks and bricks.
- Poured concrete, felled logs, or straw bales.
- Wine barrels.
- Upcycled wood, including fence boards and pallets.
- Stacked rock walls, cobblestones, and large natural stones.
- Metal like galvanized steel tubs or corrugated metal.
- Miscellaneous materials and containers such as scrap wood, used tires, kiddie pool, etc.
What Factors Should Be Considered When Choosing a Material?
Not all materials are created equal, and not all are suitable for making a raised bed. So if you want to choose the best material, you need to keep the following in mind:
If you want your raised garden bed to last for a while, you need to choose durable and robust materials. You should also remember that garden beds are almost always subjected to moisture and other outdoor elements, pests, and insects.
Wet soil is also very heavy; the greater the soil mass, the higher the pressure on the bed walls. So if you choose thin lumber, it will rot or bow, which is why you need to get higher-quality. However, note that metal or concrete beds will last more than one made with the best lumber.
Cost and durability typically go hand in hand. Better-quality materials cost more and last for quite a while. But if you opt for a cheaper option to cut down your cost, it won’t last very long, and you’ll have to invest in another one pretty soon.
For instance, a planter made of premium lumber will last twice as long as one made of soft pinewood or reclaimed pellets. Similarly, concrete blocks or large stones are more expensive than straw bales, but there’s a massive difference in the lifetime of the two.
Of course, this doesn’t mean you need to splurge on raised beds. With a bit of research, you can find a fantastic deal, and you can forage for materials on places like Facebook Marketplace, Craigslist, and even your local junkyard. So make sure to shop around and always compare prices.
If that doesn’t work out, you can make your own garden bed with felled logs.
You’ll come across many hacks telling you to use treated, salvaged, or painted wood. But you should never do that, especially if you don’t know its origin and age. The piece of wood might be contaminated with arsenic, lead, or other toxic chemicals that can eventually leach into your food.
The same goes for other upcycled materials used for raised beds, such as styrofoam coolers that contain a potential carcinogen and old car tires that contain heavy metals and toxic chemicals.
Common Materials for Raised Beds and Their Pros/Cons
Now that you know how you can choose a material, let’s go over some of the common options along with their pros and cons to make it easier for you to make your choice.
Fabric or cloth-raised garden beds are large pots made with flexible, synthetic materials. Different pieces of fabric are stitched together to make a large bag you can fill with soil. Fabric-raised beds are available in various sizes and shapes and hold soil like other raised beds.
- Since there’s no building involved, they’re easy and fast. You just need to unfold the bag and fill it with soil.
- Fabric is cheaper than other materials used for raised beds.
- Making it level is also easy, which is essential for planting and watering.
- It’s not bottomless, so mice and voles can’t tunnel into the soil.
- Fabric beds are well-draining and good conductors of air, making them great for roots and beneficial microbes.
- Fabric is better than many other materials since there’s less chance of it leaching chemicals. Most pieces are usually BPA-free.
- Fabric garden beds tend to bulge more than other ridged materials, and getting used to them is a little tricky.
- Some people don’t like that it’s not bottomless since it doesn’t allow worms and other beneficial bugs and creatures.
- Watering the edges is difficult, which is why the soil at the edges tends to dry out.
- They have a limited life and usually last for 4 years, although this number may vary.
- It’s impossible to attach season-extending covers or fencing to them.
- Shoveling out the dirt can be tricky, and you can easily damage the bed, like ripping its side when using the shovel.
The most commonly used material for raised beds is untreated wood because of how affordable and easy it is. Some type of joining device like screws and brackets is typically used to form the rectangle.
You can use different kinds of wood to make the bed but remember that the softer the wood, the shorter the lifespan. So wood like pine will only last around four years, but pine might last for up 20 years or even more. However, long-lasting woods are expensive, while softer woods are cheaper.
Suitability of Different Kinds of Wood
- Unfinished pine is an economical choice and is a good option for those trying out raised beds for the very first time. However, its natural rot resistance is limited.
- Cypress is longer-lasting than pine and is better resistant to rot, fungi, and insects. It’s also more attractive and dense, and the fine grain ensures beauty and longevity.
- Cedar is very similar to cypress in terms of longevity and aesthetics. The only difference is that it’s a little lighter than cypress.
- Redwood is characterized by its distinct beauty, but it’s hardly used because of how expensive it is.
- Inexpensive and non-toxic.
- You can adjust the height of the raised bed according to your preference. For instance, if you can’t kneel, then you can make the bed very high.
- Easy to attach the season-extending cover or fence.
- Most options don’t last very long.
- You need simple carpentry skills and some kind of joiner to make the bed.
- Since wood is inflexible, creating round beds is difficult.
- Watering the bed will make the wood wet, which will attract termites.
Composite lumber is a combination of plastic or other synthetic materials like polyethylene and wood fiber held together using a binding agent to make the boards. Most decks are made using composite lumber since it’s more durable than untreated wood and less toxic than pressure-treated wood.
It’s also rot-resistant, which is why beds made with composite lumber last longer than beds with natural wood. Some wood composites have surface patterns and textures that make them as beautiful as natural wood, and they retain that beauty without any oiling or staining.
- Lasts for a long time even if it’s put in the soil directly.
- Since it’s more flexible than untreated wood, you can bend it.
- It looks like stained wood and seems to have a finished look.
- Attaching a season-extending cover or fencing is easy.
- Even though it’s not as vulnerable as untreated wood, termites will still attack it.
- Since wood composites involve both plastic and adhesive, there’s a high chance they’ll leach toxic chemicals into the food.
- Even though it’s not as expensive as cedar, there’s still a high cost.
What Materials Should Be Avoided for Raised Beds?
We’ve discussed all the materials you can use for raised beds above. Let’s also go through the materials you should definitely stay away from:
Reclaimed or Recycled Wood
As mentioned earlier, you should avoid using wood if you don’t know how it has been treated and its age and origin. For example, the wood may be painted, stained, or treated such that it introduces toxins into your plants.
Recycling and upcycling are great options, but it’s best to avoid using things like railroad ties and discarded tires for raised beds. Even though railroad tires look great, they’re treated with creosote, a potential carcinogen. Plus, it can harm crops growing nearby or inhibit their growth.
Old wooden pallets might still be acceptable, but they might contain traces of materials put on top of them, making them a little risky. Some pallets might also be treated with insecticides or preservatives, but there’s no way to know that, so it’s better to stay away from them.
Also, avoid other risky items like used car tires, plastic products, and styrofoam. And if you’re using a plastic raised bed kit, make sure it’s made using BPA-free food-grade plastic.
Pressure-Treated or Treated Lumber
There’s a bit of a debate around this among gardeners. Pressure-treated lumber used to be cured with CCA, an arsenic-based compound. Unfortunately, arsenic is extremely harmful to your health and leaches readily from the lumber into the soil.
Even though CCA has been banned for nearly two decades and replaced by less toxic chemicals, it’s better to avoid using treated lumber. Plus, cedar and redwood last longer than pressure-treated pine, so there’s no need to opt for something that’s been chemically treated.
Plastic is durable, cheap, and sometimes attractive, so you might be tempted to use it for your raised beds. However, even good-quality plastics like HDPE have leaching issues and tend to contaminate the soil.
Bricks and Cement Blocks
Cement blocks and bricks last a long time and don’t cost much. Plus, making raised beds with cement materials is easy, and since they’re individual blocks, you can arrange them how you like and make unique shapes.
However, it’s impossible to determine where the raw material was sourced from or what was used in the first place. Typically, the cheapest possible material is used for cement blocks, which can be hazardous and contaminate the soil. And if that’s not the case, cement will increase the soil pH as it breaks down.
Plus, attaching season-extended covers or fencing securely to bricks and blocks is almost impossible.
Most people find stones to be the least expensive material for raised garden beds, more so if they already have stones present on their property.
However, since they have an irregular shape, they make things quite tricky. Creating a bed will take a lot of time since you’ll have to put together stones like a puzzle.
Metal or Steel
Metal has many advantages—it lasts for a while, is easy to assemble, and is attractive. However, it can be expensive and leach metals and chemicals into the soil, making it unsuitable for growing food.