When installing a raised beds, there’s a few things that need considering. Not only do you need to consider the width, height, soil and layout, you’ll also need to think about the building materials.
There’s a range of different materials you can use to construct a raised bed, each with their own pros and cons. While some are selected for their look or ease of installation, others have certain qualities which help improve the growing conditions of the raised beds.
Not sure where to start? We’ve put together our top 10 garden bed materials.
1. Untreated Lumber
Arguably the most traditional raised bed material, untreated wood is long lasting and suits any style of garden.This style of wood boasts natural rot resistance, although many gardeners choose to treat it with a non-toxic preservative in order to extend its lifespan.
Untreated Douglas fir is one of the more popular choices. This wood can last up to 15 years before needing replacing, and it’s also very affordable. Unlike some other materials, it’s easy to put together and work with.
It’s important that the wood is left untreated. While pressure-treated wood has been used in the past for raised beds, the coating used to treat it contains harmful chemicals which can leach into the soil and damage your plants.
Wood treated with chromated copper arsenate (CCA) is not recommended for raised beds. This treatment can leach into the soil, contaminating both plants and people. In 2003, the sale of this wood for residential use was banned by the Environmental Protection Agency.
Modern pressure treated wood doesn’t contain CCA, and has instead been treated with alkaline copper quaternary (ACQ). While this treatment doesn’t contain arsenic, it’s recommended that you don’t use this wood in a raised bed vegetable garden.
Cedar wood is another top choice for raised beds. This wood is easy to work and naturally rot resistant. With the right care, cedar can last up to 20 years.
Cedar is usually thought of as a stronger wood than untreated pine. If it’s durability you value, this is the best option. It’s resistant to bad weather, and can be used all round the garden. Cedar is often used to make garden furniture and decking, as well as raised beds.
Another advantage of this type of wood is its beauty. This material lends itself brilliantly to most gardens, complementing almost any flower display. Cedar is also biodegradable, and will slowly break down into the earth after use.
No material is perfect, and cedar has a couple of downsides. The first is that untreated cedar will fade after long-term exposure to sunlight. Many people apply a finish to prevent this from happening.
Another concern is that cedar can retain moisture, and may not last as long in very wet climates. If the UK has a particularly wet winter (as it often does!), cedar beds will be more susceptible to deterioration. Treating the wood with a non-toxic stabiliser can help to elongate its lifespan.
3. Recycled Plastic
Durable and easy to work with, recycled plastic is another good choice for raised beds. This material is resistant to cracking and chipping, even when exposed to extreme weather.
Unlike treated products, recycled plastic is stable and won’t leach toxic chemicals, or in fact any chemicals, into the soil. This makes it a great choice if you’re growing edible produce.
Plastic is also easy to maintain. After a long winter being battered by the elements, plastic garden beds can be wiped clean using either a sponge or power washer.
Another benefit is that plastic is available in a range of colours. They can be purchased in a darker finish or light colour to suit your garden.
Although durable, it’s worth noting that recycled plastic does lack the linear strength of wood. If filled with too much soil or placed on a slight slope, plastic panels can bow outwards and eventually weaken. A good solution is to purchase plastic with an aluminium bar through the middle.
Recycled plastic panels can also be costly. While durable, lightweight and easy to work with, good quality plastic raised beds can be more expensive to put together than wooden beds.
4. Galvanised Steel
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With its sleek design and impressive durability, there’s a number of benefits of galvanised steel. Unlike wooden beds, metal raised beds won’t rot or warp even after prolonged exposure to bad weather.
The only thing you need to worry about when it comes to metal beds is rust, and this is why galvanised steel is a good choice. Galvanised steel has been coated with a layer of zinc which makes it rust resistant. Provided your soil isn’t very acidic, galvanised steel raised beds can last for up to 30 years.
Another advantage is that galvanised steel can keep the soil warmer at the outer edges. On sunny days, you should find your raised beds get warmer. If there’s a sunny start to the planting season, you may be able to start planting earlier.
5. Wood Composite
Made from a blend of wood fibre and recycled polypropylene, wood composite strikes the right balance of ease of use and aesthetics. Wood composite offers the attractive appearances of wood, coupled with the easy maintenance of plastic.
Composite wooden beds can usually be put together very easily, simply stacked up to your preferred height. If you are moving house, composite wooden panels can be taken with you and put back together in your new garden.
Another benefit of composite wood is that it’s both weather and rot-resistant. It’s also easy to clean, and can be sponged off at the start of the planting season.
There’s not many downsides to wood composite. While it usually has a protective UV coating, this can weaken over time and lead to the colour fading. As composite boards are very lightweight, overfilling them or installing them on even a gentle gradient can cause the panels to bow outwards.
6. Natural Stone
Evoking a quaint, cottage-style garden feel, stone is a wonderful choice for raised beds. Natural, beautiful and sustainable, what’s not to like?
Aesthetics aside, stone is one of the most durable materials for raised garden beds. Unlike wood, stone raised beds will never rot nor be destroyed by mites. Even general wear and tear is unlikely, and any that does occur will enhance the look.
Stone is also eco-friendly. Even producing uniform stone blocks consumes less water and energy than other building materials. Stone won’t emit chemicals and it doesn’t require any treatment, so it’s a great choice if you’re growing edible produce.
Perhaps the biggest advantage of stone is its versatility. Stone can evoke a country cottage, farmhouse or even an ultra-modern feel. It comes in a range of different sizes, colours and textures.
There’s a couple of downsides. The first is that it can be expensive. While it is a natural material, buying large quantities of stone can still cost a lot of money. Stone can also be heavy, so putting together a raised bed made from this material will require a lot of labour. If you are moving house, you may struggle to take a stone raised bed with you! For this reason, you’ll need to think carefully about the size, shape and location of your raised beds.
7. Concrete or Cement Blocks
Concrete can be used to make an attractive and contemporary raised bed. Smaller blocks are easy to arrange, allowing you to change the layout of your raised bed whenever you like.
Concrete blocks are exceptionally durable. They can last up to 100 years before they start to deteriorate. Compare this to wood, which may last for just 10 years. If you’re after value for money, concrete blocks are up there with the best.
If built correctly, concrete block raised beds can be very sturdy. They won’t bend or warp, even when placed on uneven ground.
Concrete retains heat very well, which does mean that during a heatwave you may need to water more frequently.
An advantage which is unique to concrete blocks is that they can also give you more planting space. The holes inside each block can be filled with soil and used to grow individual plants.
It’s worth noting that concrete blocks are heavy. Weighing around 15 kg each, you may need an extra pair of hands to build a raised bed made from concrete blocks.
8. Upcycled Materials
Eco-conscious gardeners should consider using upcycled materials for their raised beds. Chests of drawers, wooden shelves or even an unwanted barbecue can be used to create a charming and eco-friendly bed.
In fact, raised bed gardens can be made from almost anything, provided the material doesn’t contain toxic chemicals.
If you want to use pressure-treated wood furniture for your raised beds, you shouldn’t grow anything edible. It’s best practice to also use a thick liner to ensure the wood doesn’t touch the soil.
Wood pallets are another good option. These can be picked up very cheaply and used to make simple beds. However, you should avoid second hand stained pallets, as well as old pallets with a MB (methyl bromide) stamp. These can leach chemicals into the surrounding soil and plants. If the plants are consumed, they can affect human health.
9. Cinder Blocks
Affordable, attractive and long lasting, cinder blocks have a lot of benefits when it comes to raised bed gardens. They allow for a more flexible design thanks to their smaller size. You’ll be able to incorporate curves into your raised beds, and it’s easy to build the bed to your preferred height.
Cinder blocks can be picked up cheaply. If one block becomes damaged, it can simply be removed and replaced with another. Wood on the other hand, can’t be easily adjusted once it’s been installed.
Cinder blocks are also very durable. They won’t rot nor break down, even after prolonged exposure to very wet weather.
There’s a couple of disadvantages to think about. The first is that cinder blocks are fairly heavy. This can make installation tricky, particularly if you’re building your raised bed alone.
Cinder blocks can also trap heat within the soil. This can extend your growing season, but it also means you’ll need to water more often. Some plants may get too warm during a very hot summer.
Like cinder blocks, brick is exceptionally sturdy and very long lasting. Brick beds are perfect for both formal and informal garden settings, and have the added advantage of being virtually maintenance-free.
One of the best things about this material is that individual bricks are small enough to give you ample flexibility when it comes to the shape and size of your raised bed. When putting a brick bed together, it’s easy to get creative, incorporative curves or contoured walls.
Another benefit of brick is that it’s a good insulator. Brick can help absorb heat from the sun during the day, keeping the soil warmer for long periods of time. While this may mean you need to water more frequently in the summer, many gardeners find a warmer soil temperature means they can sow their seeds earlier in the year.
Installing a brick raised bed is very easy. Taller raised beds will require mortar or cement to hold the bricks together, but if you’re making a smaller bed, the bricks can simply be stacked on top of each other.
What is the best filling for a raised bed?
This depends on what you are growing. While some plants prefer a nutrient-rich soil, others are happier in poorer quality mixes.
The best all-round mix for raised beds is thought to be 60% topsoil, 30% compost and 10% potting soil such as perlite.
What is the cheapest way to make raised beds?
The cheapest way to make a raised bed is to use materials that are easy and affordable to source. Raw wood, upcycled furniture and untreated pine lumber tend to be the cheapest materials.
Raised beds can be made from almost any material that’ll hold soil. If you’re able to get hold of some leftover bricks, these are a great option.
On the other hand, any container which is stable and deep enough to allow plant roots to spread can be used to make a raised bed.
What wood should not be used for raised beds?
While many different varieties of wood can be used for raised beds, care needs to be taken if the wood is pressure-treated.
This is because pressure-treated lumber contains chemicals which can leach into the soil and affect your plants. While newer pressure treated wood is safer, it still shouldn’t be used if you are growing edible produce, as plants can absorb the preservatives.
Older pressure-treated wood can still be used to make a raised bed, but you should ensure you have a thick liner which will prevent the wood from making contact with the soil.