Whether you are starting a new garden or adding to your existing garden, knowing how to construct your raised bed garden is the first step. A raised bed garden is just what it says—a garden that is raised above the ground level. Most raised beds are built to be able to accommodate amended soil between six and 12 inches deep. While you can have the soil raised up without a method of keeping the soil contained, most raised beds are edged with some type of structure. This holds the shape of the raised bed and prevents erosion during the garden season from rain and use. The soil is rich in organic material and will grow much more in a smaller space than the traditional garden rows grown in a ground level garden. Raised beds are rarely walked on, and because the vegetables or flowers are grown intensively, they minimize the number of weeds. This is a great contrast to the traditional garden that requires frequent hoeing or rototilling to keep the soil from compacting and to keep the weeds under control.
Things to Consider When Choosing Materials for a Raised Garden Bed
The material you use to make the walls of your raised garden beds can vary. Most often when we think of a raised bed garden, the wood boxes come to mind. These are probably the most common. However, there are other options. Your raised bed walls can be made from rocks, paver stones, metal or plastic. Each has advantages and disadvantages.
There are a few concerns that will determine the materials you will use to make your raised bed garden. The first is cost. If you are just starting out on your gardening adventure, cost may be the determining factor. You may need to repurpose materials for your garden or use material that is a lower grade than you would prefer. Your raised beds may not have the longevity that you would wish for, but it will work for a number of years. Remember that soil is heavy and when soaked with rain, even heavier. Whatever material you use must be able to withstand that outward pressure on the walls of your raised beds.
A disabled or elderly gardener may need a tabletop height to their garden so that they can avoid bending or stooping. If wheelchair bound, the raised bed needs to allow the wheelchair to fit under the raised bed so the gardener can easily work in the garden. In this case, the raised bed includes a bottom that needs to be strong enough to support the weight of the soil as well as any outward pressure.
Materials to Choose from When Building a Raised Bed Garden
Here are some materials you may consider for your raised bed garden, along with advantages and disadvantages to each.
1. Wood Raised Garden Beds
Wood is usually the first choice for a raised bed garden. Wood is available and sustainable. Even if you are not a skilled carpenter, most gardeners are capable of forming a frame for a raised bed that is positioned on the ground. If you need a tabletop height raised bed, the structure will need legs and stability, as well as the ability to support the weight. This may be a job you hire a professional to do.
The type of wood you use can also vary. The construction will remain the same; however, the type of wood you use will definitely impact the longevity of your raised beds. Another critical factor in determining the life of your raised bed is the thickness of the wood used. Ideally, the wood boards should be two inches thick. Redwood and cedar are great choices. Both woods contain natural tannins, a substance that repels rot and even termites. Both woods can last 10-20 years or more in your garden. When purchasing either, comparison shop. There can be a significant difference in price between the redwood and cedar based on your geographical location. Also, don’t assume the Big Box store will always be cheaper. Check the local lumber yards as well.
Other woods can also be used. Hardwoods such as oak, teak, maple, walnut and beech are also good choices with good longevity. Softwoods will work well and be less expensive. The disadvantage is they don’t have the same longevity as hardwood. Softwoods include pine, Douglas fir, juniper and spruce. Softwoods have a lifetime of four to seven years, depending on your climate.
The choice of which type of wood to use for your raised beds may very well come down to affordability vs. longevity. But with that in mind, repurposed wood might be the best option for you. There are raised beds made from repurposed wood pallets or other woods that have been reclaimed. The problem is that you may not know if this wood has been treated with any toxic chemicals or paints that would make it inappropriate for edible gardens. Check Craigslist and other similar sites for lumber as well as resale shops like Habitat for Humanity stores.
Some people like to use a sealant on the wood to increase the life of the wood. This could be very helpful if you have opted for a softwood to make your raised beds. Make sure that the sealant you use is a non-toxic sealer. If you choose a hardwood for your construction, using a sealant is more an aesthetic choice. Many people prefer the look of the naturally aging wood. The fresh redwood will have a pinkish color that gradually turns to a soft silver grey that many people find very attractive.
2. Composite Wood Raised Garden Beds
This is the material that many decks and porches are now made with. Composite is made with wood particles along with synthetic substances such as polyethylene. The resulting product looks like wood, but resists rot and therefore has a much longer lifespan. They maintain their original look without needing staining or oiling. This material is used as you would use regular wood boards. Check out this guide for building a composite wood raised bed garden.
3. Metal Raised Garden Beds
Another option is making the sides of the bed out of corrugated metal. The metal can be encased in a wood frame or just attached to wood corner posts. The corrugated metal can be purchased new or use reclaimed material. While a type of corrugated metal roofing is now very popular for replacement roofing or on new builds of homes, it has been used for many years on farm buildings. If you live in a rural area, this may be an opportunity to procure corrugated metal very inexpensively when an older building is being replaced.
Steel Raised Bed Garden
An ideal combination of DIY and DIFM, the Vego raised bed is lightweight but extremely durable, lasting for 20 years or more. It’s easy to assemble (DIFM) and developed and finished with materials that are 100% non-toxic. The components that you easily screw together are interchangeable so you can create your ideal garden configuration (DIY). It has rounded corners and smooth edges so it’s safe for kids, clothing, and hands.
The Vego bed has the environment in mind too. In addition to its 20-year+ longevity, which saves you money, it’s also recyclable. To support your outdoor lifestyle, we also have add-ons – lights and trellises -- that make the garden bed a natural addition to your outdoor décor. There’s even an in-bed composter to make reusing your kitchen waste simple.
4. Raised Garden Bed Containers
Your raised bed garden can be in containers such as old garden pots, an unused wheelbarrow, a child’s plastic swimming pool and wine or whiskey barrels. Really, any container will work as long as it is not chemically treated with toxic or hazardous substances. Grow tomatoes in pots on that often-ignored side yard. Start tomato seeds indoors and transplant outside when the weather allows. Place a row of pots along the side of the house with a single tomato plant in each pot.
Fill the old, unused swimming pool with soil and plant everbearing strawberries in it. Another option is to use the kiddie pool for salad greens. Plant an organic vegetable seed mix of different lettuces, along with some arugula and spinach. You will be enjoying fresh salad all season. It doesn’t matter if the pool was leaking in its original life—now, a few drainage holes in the bottom are an advantage.
Add soil to the leaking wheelbarrow and plant with flowers or organic vegetable seeds of vining crops like cucumbers and allow them to grow over the sides of the wheelbarrow. It will look decorative, and you can harvest a bounty of fresh organic vegetables.
Another container to consider for your raised bed garden is galvanized water troughs for livestock. These can be placed anywhere in your garden and can be moved if needed. They are ready to use when purchased—no construction necessary. Remember the entire container does not have to be filled with soil, only the top six to 12 inches. The bottom can be filled with any organic material, including small logs or brush. If you have material like used Styrofoam shipping peanuts, rather than send that material to a landfill, use it to fill the bottom of your containers.
Today, there are companies who make galvanized raised beds for purchase. These come in many shapes and sizes and have great longevity. If you like the look of galvanized metal, this could be the perfect choice for you.
5. Raised Garden Beds Made of Pavers, Bricks and Cement Blocks
This material will last forever. This can be an advantage as well as a disadvantage. Obviously, the first advantage is the longevity of your raised beds. Pavers, bricks and cement blocks will last you a lifetime. You will not need to replace the material so the expense can be spread over your gardening lifetime. If the stone you choose is just stacked (no adhesive is used), the walls are technically movable. If you change your mind on the design or your gardening needs change, the stone walls can be dismantled and reassembled elsewhere. If, however, the stone requires a masonry adhesive or cement for safety or stability, the wall will be permanent.
Pavers and bricks are very attractive and could be ideal for the high visibility front yard. They also can be used for curved beds where wood boards won’t be usable. However, here’s one caution about pavers, bricks and blocks. Many have the added ingredient of fly ash in these manufactured stones. Fly ash will increase the durability of the pavers and bricks. Fly ash contains arsenic and radium. There are no studies available on whether these elements can leach out of the stone and into the soil. Check with the manufacturer to determine if fly ash is used in the pavers you have chosen.
6. Natural Stone Raised Garden Beds
This is stone like limestone, flagstone or rocks. While some stones can be dry stacked like the walls of homes throughout New England, others will require an adhesive or even cement. Small rocks cemented together make a very attractive fieldstone wall. Your wall can also include tiles, pottery and even glass bottles. It can be as eclectic as you choose.
Products to Avoid When Building a Raised Bed Garden
When building your garden bed, there are a few things to avoid (including looking for fly ash in your pavers and bricks). These products include railroad ties and pressure-treated lumber. Both of these items can be toxic to your soil and the plants around them, particularly over time. In fact, pressure-treated lumber was originally treated with a form of arsenic called CCA (Chromated Copper Arsenate). So if you have old pressure-treated lumber lying around and you burn waste material, it’s important not to let this lumber burn or enter your compost pile. The good news is, they switched from CCA to copper in more recent years. The bad news? It can still leach into your soil and isn’t approved for organically certified growing.
Another frequently used Pinterest repurposing idea is to use old tires filled with soil. Tires are notorious for leaching toxic chemicals into the soil. Avoid those as well.
Add Raised Beds to Your Garden
Building raised bed gardens can be simply functional or an example of your creativity. Remember that they don’t all have to be the same. You may choose to use a more formal paver in the front yard foundation planting, while in the backyard, you have a rainbow of water troughs each painted in a different color for your vegetable garden. The shape of your beds can also be a design feature. Your beds can be triangles if that is what fits in the space you have available. There are no rules when it comes to making your garden reflect you.
