To build a raised garden bed, the first step is to choose the right building material. There are lots of possibilities – some are cheap and easy to find, while others are more expensive and durable.
So, what material is best for raised garden beds? The best materials for raised garden beds are stone, plastic such as HDPE, and durable wood, such as cypress, cedar, and redwood. These materials will stand up well against damage caused by exposure to water, soil, and insects.
Of course, there are other materials you can use for building a raised garden bed, such as metal. Durability is one consideration, but you also need to think about the cost, safety, and difficulty of working with the material you choose.
In this article, we’ll take a closer look at the materials you can use for raised garden beds. I’ll also give some recommendations on the scenarios where each material works best.
Let’s get started.
Best Material For Raised Garden Beds
The best materials to use for raised garden beds are:
- Stone (I’ll include bricks, pavers, and concrete in this category)
- Plastic (the best plastic option is a durable and safe recycled plastic, such as HDPE)
- Wood (redwood is one of the most durable types of wood, followed by cedar, and then cypress. Oak and pine will not last long when exposed to water, soil, and insects.)
You can also use metal for raised garden beds, but it can be dangerous when there are sharp cut edges. Even worse, untreated iron and steel are prone to rust.
The material you decide to use will depend on where you live, how much you want to spend, and how long you want the raised bed to last.
Let’s start off by looking at the pros and cons of using stone for your raised beds.
Stone For Raised Garden Beds
Stone is one of the most durable materials you can use for building a raised garden bed. Why do you think some castles (which were made of stone and built hundreds of years ago) are still standing?
I’ll include bricks, pavers, cinder blocks, and concrete in this category, along with ordinary rocks you would find in your backyard. There are several benefits to using this material for building raised garden beds.
Pros Of Stone
- Stone is extremely durable. There is no chance of insects chewing through it, and it will take many years for water and wind to damage it enough to wear it down even slightly.
- Stone is widely available and easy to find. You can get rocks for free from your backyard or from a neighbor. You might even be able to pick them up from a construction site (ask the foreman first!) Bricks, pavers, cinder blocks, and concrete are all easy to find at garden centers, including Home Depot and Lowe’s.
- Stone absorbs lots of heat, so it can warm up quickly in the sun. This can be helpful if you need to warm up the soil early in the season when the sun is out, but temperatures are still low.
Although sturdy and widely available, stone does have drawbacks as well.
Cons Of Stone
- Stone is heavy, and much more difficult to work with than wood or plastic. Once you build a raised bed out of stone, it will not be easy to move! Even worse, you can easily injure yourself on a DIY project when moving heavy stones.
- A tall raised garden bed made of stone can be unstable. You may need to use cement (you can also hire a mason) to hold it all together, making the project more expensive or time-consuming.
- Stone can be expensive. If you need to buy it at retail prices from a garden center or a landscaping supply company, expect to pay a lot.
- If you live in a hot climate, stone may absorb too much heat. This will make the soil in your raised bed too hot for some plants.
- Cinder blocks may contain fly ash, a by-product of burning coal. As such, it may contain heavy metals or other environmental hazards. According to the University of Maryland Extension, you can seal cinder blocks with a polymer paint to avoid this hazard.
Of course, if you are worried about toxicity from cinder blocks, you can choose to use another type of stone instead.
When To Use Stone
Stone is a great building material for raised garden beds in the following situations:
Stone is a good choice if you live in a cold climate with a short growing season. A raised bed made of stone will warm up the soil it contains.
The stones will transfer heat to the soil in the raised garden bed, which will heat up faster than the soil in the ground. This will let you plant outside earlier in the season.
It will also let your plants survive later into the fall. Having warmer soil and a longer growing season is especially important for warm-weather crops, such as tomatoes, peppers, and cucumbers.
If you can gain a week at both ends of the growing season, it can make a big difference for frost-sensitive plants.
Stone is also a good alternative to wood in areas with high humidity (such as Florida). In these areas, most untreated wood will rot quickly if exposed to water, soil, and insects.
If you live in Florida or other warm climates, be careful about the heat retained by stone. Plants that are sensitive to heat may not do well on hot days if you put them in a raised bed made of stone.
If there are lots of rocks in your yard (or in a neighbor’s yard), then you have the perfect source of stone for building your raised beds! Just be sure to get help so that you don’t get hurt moving large stones.
Plastic For Raised Garden Beds
If stone is too heavy for your purposes, then consider using plastic instead. Plastic is one of the lightest building materials you can use for a raised garden bed. In fact, there are several additional benefits to using plastic.
Pros Of Plastic
- Plastic is light, compared to stone, wood, and metal. If you ever decide to move your raised bed, it will be much easier if you build it with plastic. You might even be able to disassemble a plastic raised bed and take it with you when you move to a new home!
- Plastic is rot resistant, and will hold up well against water, soil, and insects. This makes it a great alternative to wood if you want long-lasting raised beds that won’t rot.
- Plastic can be found in many colors. You can choose a lighter color (such as white or tan) to absorb less sunlight and heat. On the other hand, you can choose a darker color (such as black or dark grey) to absorb more sunlight and heat to keep the soil warmer.
- Plastic is widely available and easy to find. There are many raised garden bed kits to choose from, such as these from Gardener’s Supply Company. You can also buy plastic “boards”, made of HDPE (high density polyethylene) or other recycled materials. Use these boards, cut them to size, and build your own custom raised bed with any dimensions you want. For example, you can find these plastic boards at Menard’s.
Cons Of Plastic
Although there are many advantages to using plastic for raised beds, there are some disadvantages as well.
- Some plastic will wear down and crack over time due to sun exposure. This is more likely with thinner, cheaper blends of plastic.
- Thin plastic may not hold up well against the weight of wet soil. This can lead to cracking – and it is more likely with taller raised beds, which are holding more soil and thus more weight.
Of course, you can always choose a thick plastic board if you are worried about the weight of the soil.
When To Use Plastic
Plastic is great for building raised beds in the following situations:
Plastic is another good alternative to wood in areas with high humidity. Plastic does not rot in moist, humid environments like wood does.
If temperatures are high, choose a lighter color of plastic. That way, the plastic will not absorb so much heat from sunlight, and the soil will not get hot enough to hurt your plants.
You Move Frequently
If you move your raised beds frequently, it makes sense to build them out of a lighter plastic material. If you move to a new home frequently, then you might be able to take plastic raised beds with you.
Wood For Raised Garden Beds
Wood is a less durable material than stone, and it is susceptible to rot, unlike plastic. So, why use wood at all?
Well, wood is lighter than stone, and easier to work with. You don’t need to use any cement to hold wood together – a few nails or screws will do it.
Some people also prefer the appearance of wood over stone, plastic, or metal, since it looks more natural in a garden.
I include lumber, sticks, and logs in this category. There are several advantages to using wood for your raised bed.
Pros Of Wood
- Wood is sturdy, yet easy to work with. While not as tough as stone, wood will hold up well until it begins to rot (this may not happen for several years with more durable or treated wood). It is also lighter than stone, making it less likely that you will injure yourself working with it.
- Wood is common and widely available. Whether you use sticks, logs, or lumber to build your raised bed, you will be able to find a source of wood easily.
- Wood will eventually rot, meaning it is environmentally friendly (biodegradable). If the wood is untreated, you can just use the old rotted wood as mulch, or add it to your compost pile, whenever you build a new raised bed.
- There are many raised garden bed kits and plans that use wood. You should have no trouble finding one that works for you. For example, here is a wood raised garden bed kit from Etsy.
You can also cut wooden boards to size and create your own custom raised garden bed.
Cons Of Wood
Although there are some redeeming qualities of wood, it also has some serious drawbacks.
- Older wood may contain toxic chemicals. Some types of wood are treated with chemicals that can leach into soil. Your plants (including vegetables!) may later absorb these chemicals from the soil. For example, old railroad ties are treated with creosote, which contains lots of nasty chemicals. Older pressure-treated wood can also contain CCA (chromated copper arsenic), another nasty chemical. This will be less of a problem as time goes on, but you will still need to source your wood carefully to avoid this.
- Wood is susceptible to damage from exposure to soil, rain, and insects. Wood will eventually rot, especially if it comes in direct contact with wet soil. It may also attract insects that want to feed on the wood or live in it (termites or carpenter ants).
When To Use Wood
Wood is a good choice for building a raised bed in the following situations:
You Want A Biodegradable Raised Bed
Rotting wood may not be a problem if you want a temporary structure. When untreated wood rots, you can use the remains as mulch or as part of your compost pile.
You can then build new raised beds out of wood in a new location. This might be helpful if you like to experiment with growing in different locations in your garden (especially if different areas get different amounts of sunlight).
It can be overwhelming to decide what kind of wood you should use for a raised bed. To help you get started, here are some types of wood you can use, in order from least to most rot-resistant:
- Pine – a softer wood that is often used for furniture. It is not as useful for outdoor projects. Pine does not hold up well when exposed to soil, water, and insects. This wood will rot within 5 years of exposure to the elements – and possibly faster in high humidity locations, such as Florida.
- Oak – a hard wood that is more difficult to work with than pine. Oak boards will last longer than pine when used to build a raised bed. However, time will still lead to decay and you will eventually need to replace oak.
- Cypress – a soft wood that nonetheless holds up fairly well against rot when in contact with wet soil. Cypress has naturals oil that acts as preservative. This allows it to resist damage from decay and insects.
- Cedar – a soft wood that holds up very well against rot in outdoor conditions. Like cypress, it contains natural oils that help to preserve it and protect against rot and insects. However, its appearance will naturally fade over time before it eventually rots. Cedar is more expensive than other types of wood, which may make the cost prohibitive for building lots of raised garden beds.
- Redwood – a soft wood that lasts quite a long time, even in outdoor conditions when exposed to wet soil and insects. Redwood is very expensive, but it can last up to 30 years. Use this is you know that you will never move your raised beds!
You might want to use a waterproof finish or stain to preserve the wood and make rot proof raised beds. Just be sure to use a safe, non-toxic wood stain (such as this one from Vermont Natural Coatings, which is made with juniper.)
By treating wood, you will avoid touching nasty chemicals or getting them in your garden (more on this later).
You Have Leftover Wood From Another Project
If you have leftover wood from another project, you can use it to build a raised bed instead of throwing it away. You can also harvest wood from a demolition project if it is still in good shape.
However, you will need to make sure that the wood is safe to use for gardening before you build! Lots of older wood is treated with chemicals that you don’t want anywhere near your vegetable garden.
- Railroad ties are treated with creosote, which can have lots of nasty chemicals in it.
- Old pressure-treated wood may be treated with CCA (chromated copper arsenate), a preservative that uses copper as a fungicide. Sun and rain can cause arsenic to leach out of wood treated with CCA, so avoid using it for raised beds or other outdoor construction projects in your yard!
There are a few ways to treat wood to protect it against the elements and prevent rotting.
One way is to use an oil-based stain on the wood. Go with a newer product – if you have old wood stain from decades ago lying around, it could contain harmful chemicals that are just as bad as creosote or CCA.
You can also use exterior latex paint to seal wood against damage from water, soil, and insects. Use a lighter color if you want the wood (and soil) to absorb less heat. Use a darker color to keep the soil in the raised bed warmer.
Another option to protect a wooden raised bed from the elements is to use a raised bed liner. The most common ones are made of waterproof plastic, which will keep the wood dry and slow down rotting.
You can use these waterproof liners on both the inside and outside of the raised bed to protect both sides of the wood from rotting.
There are pros and cons to using a plastic raised bed liner, but I think they are worth it overall. I wrote an article all about raised bed liners, so you can learn more about them here.
Metal For Raised Garden Beds
Metal is a tough material, and it won’t rot. However, it can be difficult to work with, and it will rust unless treated. Here are some pros of using metal for your raised bed:
Pros Of Metal
- Metal is strong, and will be able to hold lots of wet soil without buckling under the weight. Plastic (and even some types of wood) will not hold up so well against all that weight.
- You can use a metal stock tank (from an animal feed/grain store) as a ready-made raised bed.
- You may be able to source sheets of scrap metal for free or cheap from a junkyard or junk dealer. This will reduce your cost of building your own raised bed.
- You can put a metal sheet against an existing chain link fence to give you one of the sides for a raised bed. The metal sheet will prevent soil from falling through the chain link fence, while the fence will give you one wall for “free”. You can then build the rest of the raised bed out of whatever you want.
Cons Of Metal
Although there are some benefits of using metal for raised beds, there are drawbacks to consider as well.
- Metal will heat up quickly in the sun. This will warm the soil too much on hot, sunny days.
- Iron or steel will eventually rust, unless treated.
- Metal can be a hazard to children or pets, due to sharp edges, rust, or hot metal.
When To Use Metal
If you want something lighter than stone, stronger than plastic, and rot-resistant, then metal is your best option. However, if you need to keep your yard “kid-safe” or “pet-safe”, then building a raised bed out of metal is not a good idea.
Materials To Avoid Using For Raised Garden Beds
When building a raised bed or gardening container, avoid anything that could leach harmful chemicals into your soil. This includes some of the items mentioned earlier, including:
- Railroad ties (due to creosote)
- Old pallets and pressure treated lumber (due to CCA)
- Old tires
Even if you are not growing vegetables, it is still a good idea to avoid these materials for raised beds or gardening. Pollinators, such as bees, will visit the flowers of these plants, and they could be exposed to the harmful chemicals.
Alternatives To Raised Garden Beds
If you don’t want to build a raised garden bed, there are some alternatives to consider:
- Straw Bales – you can set up a long, narrow row of straw bales and use them for growing your vegetables. For example, you can grow potatoes in straw bales.
- Grow Bags – you can also use grow bags for vegetables or flowers. You can even use larger grow bags for dwarf fruit trees. If you put a group of grow bags together in a row, you can create a “raised bed” without going to the trouble of constructing one. You can move them during the season to take advantage of sun or shade in your yard. You can learn more about the pros & cons of grow bags here.
- Soil Mounds – this is the most basic type of raised bed ever! You don’t need to construct anything, use any nails, lay down any straw, or buy any grow bags! All you need do is mound up some soil and grow your plants right on top of the mound! Potatoes, sweet potatoes, and other vegetables are well-suited to mounding, so it’s something to consider.
Now you know the pros and cons of the materials you can use for building raised garden beds. Hopefully, you will have an easier time deciding which material is best for your garden.
You might also want to read my article on how to cover a raised garden bed.
I hope you found this article helpful – if so, please share it with someone who will find the information useful. It’s time to start building your raised bed and make it last!