What material should I use for a raised garden bed, you want to know? Well, it depends on your personal preferences, style, budget, climate, and what material works best for you. Let's explore the options!
This article will cover the most common (and less common) materials used to make raised garden beds, including wood, metal, concrete, and more. We'll discuss things to consider when choosing a material, such as durability or safety, and the differences between various types of wood. Finally, don't miss our list of potential raised bed materials we recommend avoiding for organic gardening.
A common material for building raised garden beds is wood
, including hardwood or softwood options
Metal, such as corrugated metal or galvanized steel drums
Brick, cinder block, or concrete block
felled logs pouring
concrete
barrel
Straw bales
Large natural stones, pebbles or stacked rock walls
Pallets, fence boards or other reclaimed wood
Other miscellaneous containers or materials
Choosing the Best Material for Garden Beds
In addition to the ones listed above, you can use just about anything that can hold soil and plants to make raised garden beds! Children's pools, old tires, scrap wood found on the side of the road...the options seem endless. However, there are many factors to consider when deciding on the best material to use. Not all people are created equal!
longevity
Choose strong, durable materials for your raised garden beds if you want them to last. After all, garden beds are subject to near-constant humidity, outdoor elements, and potential insects or pests such as termites. Plus, the soil is heavy - especially when it's wet! The more soil mass that is present (such as in a large or raised garden bed), the greater the pressure on the bed walls. In this case, the veneer can easily warp or rot. Even the best wood, concrete or metal bed will outlast a wooden loft bed. We discuss more about the best wood choices for building a raised bed below.
EDIT: Check out this newer post with 7 ways to make your wooden raised garden beds last as long as possible, with info on sealing, silicone and more!
cost
Most (but not always!) costs are directly related to durability. Higher cost, higher quality materials have the potential to last for decades or more. If you choose to save money up front and choose more affordable materials, you may be sacrificing the life of your loft bed. For example, a planter made from recycled pallets or soft pine may not be half as long as a planter made from quality wood. Also, large rocks or concrete blocks are more expensive than straw bales, but last a lifetime in comparison!
Now, that doesn't mean you have to spend a fortune building a raised garden bed! Depending on your situation, you may be more willing to give up a bit of longevity to reduce upfront costs - especially if you're renting out your current home, or just building a temporary garden space. There are also plenty of ways to be resourceful and find lots of stuff. Visit your local Craigslist, Facebook marketplace, junkyard, etc. to find material. Heck, if you have easy access to large felled logs, you can make a very durable and affordable bed.
Finally, you must shop around and compare prices. For example, we are able to find an abundance of stone, blocks, gravel, bulk soil, and mulch (and many more types of materials) at our locally owned landscape supply company. However, it turns out that lumber can be expensive at local stores and more affordable at big box hardware stores.
Safety
There are tons of creative and budget-friendly raised garden bed "hacks" out there - but I urge you to use some common sense! For example, I would think twice before using painted or treated reclaimed wood to make flower beds for edible crops. Especially when the age and origin are unknown! Wood can be contaminated with toxic chemicals such as lead, arsenic, or other heavy metals that can migrate (leach) into soil and food. Even though modern pressure treated wood is less toxic than the materials they were made in the past, I would still advise against its use.
I've seen people make garden beds out of all sorts of recycled materials: polystyrene coolers (made of polystyrene, suspected carcinogen) or old car ties (contains benzene, polycyclic aromatic hydrocarbons, heavy metals, and many others that are harmful to human health) Substance). While I appreciate efforts to reuse items in the name of sustainability, I personally don't think it's worth the risk. See the following sections for a complete list of materials to avoid.
Types of wood used to make raised garden beds
cedar or mahogany
Cedar and redwood are two of the best wood choices for building raised garden beds. They are all extremely durable, beautiful, and naturally resistant to moisture, corrosion, and even termites. Depending on where you live, the cost per person can vary greatly. We've found that redwood is more affordable on the west coast, while cedar is more readily available in the eastern US, and therefore less expensive.
A raised garden bed made of mahogany or cedar should last a decade or more! After all, the water storage tanks used to be built of mahogany! Cedar and redwood are technically "softwood" woods, but both contain high levels of natural tannins (which protect against rot and termites), which make them more durable than other softwoods. Due to its higher tannin content, rosewood is rumored to have a shelf life of several years longer than cedar—especially if you use heart rosewood.
When you browse the wood department, you should see options for "Common Grade" Rosewood or Heart Rosewood - sometimes called Architectural Heart, "Conheart" or Heart B Rosewood. We make our loft beds from mahogany, which is denser than common grades of wood or sapwood and therefore more durable.
Whenever possible, choose wood with FSC certification. The Forest Stewardship Council certifies wood from "responsibly managed forests that provide environmental, social and economic benefits."
Other Wood Options for Loft Beds
Generally speaking, hardwood lumber is denser, so it has more durability and strength than softwood lumber. Examples of durable hardwoods include teak, maple, beech, hemlock, walnut, locust, and oak. Oak barrels are made from oak wood, which both enhances the flavor of the wine and provides incredible moisture resistance and persistence. We use wine barrels extensively in our garden as raised garden beds! Be sure to drill at least six drainage holes in the bottom using a 1/2" to 3/4" drill bit.
Hardwoods, though strong, grow more slowly and are therefore far less common in construction than softwoods. Popular softwoods include Douglas fir, pine, spruce, and juniper. These options are often more affordable than mahogany or cedar, but are less durable. Raised garden beds made from these softwoods are known to last an average of 4 to 7 years (compared to 10 to 20 years for cedar or redwood), depending on the local climate.
Another thing to consider is the size of the wood. The thickness of the plank also directly affects the lifespan of the garden bed. Raised garden beds made from 2" planks are more durable than beds made from 1" planks or ½" fence planks - so far! We used heart mahogany 2×6" planks to build our loft bed.
Learn how we made our wood frame bed with this step-by-step tutorial (including video)! Or, check out some sturdy, easy-to-assemble loft bed kits here.
For our backyard garden (a few years ago, when we still had grass!), we built mahogany raised beds around the patio, with a trellis attached to the back, which also doubled as a chicken-proof fence. We also use wine barrels to grow tomatoes, turmeric, cannabis, herbs and more.
Should I seal my wooden garden beds?
This is another "it depends" situation! Redwood and cedar have absolutely no need for a protective sealant, but may benefit in climates with high humidity or precipitation. If you choose to seal wood garden beds, choose a non-toxic sealer such as GardenSeal or Hope's NaturalTungOil. Softer wood options will benefit more from the extra protection of the sealer. Follow the manufacturer's recommendations on how often to apply a new coat.
Personally, we don't seal our redwood garden beds, but we do live in a fairly dry climate! Sometimes foggy...but very dry. We also love the way the mahogany ages naturally, untouched. It starts out as a beautiful pink and turns to a slightly amber shade within a year before fading to a beautiful beach barn gray. Cedar also ages gracefully over time, turning from reddish-brown to silver-gray (unless a sealer is used frequently).
EDIT: Since moving to our new homestead and building our forever garden, we did choose to seal the insides of our new redwood raised beds with several layers of garden seal to extend their life.
metal raised garden bed
Metal raised garden beds are becoming more and more popular! They are modern, stylish and extremely durable. Unlike wooden beds, metal beds don't rot over time, swell and shrink with moisture, and don't require a lot of maintenance. That said, galvanized steel raised garden beds are an excellent choice for super humid climates! Some people may be concerned that the metal bed will heat their soil, but that's nothing to worry about. Even if the metal is warm to the touch, moist soil does a good job of cushioning temperature swings. I know many hot climate gardeners who use metal raised garden beds, no problem.
There are many metal garden beds to choose from. You can make your own using corrugated metal sheets inside a wooden frame. Or, turn prefabricated metal containers into raised garden beds, such as adding drainage holes in the bottom of galvanized steel animal feeding or water tanks.
Last but not least, there are tons of really cool metal garden bed kits out there! My friend Kevin just started selling some super durable and stylish Birdies garden bed kits, shown below. They can be made in various shapes and sizes and were previously only available in Australia. (Use code "deannacat3" here to save 5% on Birdies beds!) Gardener's Supply Company also offers a range of premium galvanized steel options, like this modular bed set.
No matter which direction you go, be sure to use galvanized metal so the bed doesn't rust!
Are galvanized steel garden beds safe?
Yes, well-made galvanized steel garden beds are safe for growing food! (Beware of well-made ones, so choose reputable, word-of-mouth products!) Steel is an alloy of iron and carbon. Through the galvanizing process, the steel is coated with a layer of zinc, which effectively seals and prevents corrosion and rust. Large amounts of zinc are unlikely to leach from the coating into the soil. Zinc coatings require very acidic conditions and take many years to break down.
Even so, Zinc is not a bad guy! Instead, Zinc is a mineral that occurs naturally in soil and is an essential micronutrient for plant growth! Plants rely on zinc to promote healthy root development, increase resistance to cold temperatures, and support other phytochemical processes such as chlorophyll formation. However, if the inside of your galvanized steel beds starts to corrode significantly, it's best to play it safe and replace them.
Make raised garden beds from concrete, bricks or cinder blocks
As with garden beds made of metal, raised garden beds constructed of concrete pavers, cinder blocks, or bricks have the potential to be extremely durable and strong. However, this category requires some caution! The installation of concrete block garden beds requires a considerable investment, especially if you use mortar or adhesives to hold them in place. They are heavy and create a more permanent design than other options, limiting your flexibility to make changes.
If you keep them fairly shallow, you can use pavers or blocks without adhesive (such as simple stacked blocks) to make garden beds. However, if you are building a stronger unit in an area prone to heavy rain or flooding, on a slope, or otherwise, you will need to secure them in place. Also find interlocking blocks for use in mortarless wall systems.
We made some elevated garden areas out of concrete blocks and secured them with construction concrete adhesive (the same way we make our concrete block greenhouse foundations). The adhesive might not be completely non-toxic, but we only used a small bead of glue deep between each piece. Also, most of these beds are decorative rather than edible. Just be sure to let the adhesive dry and fully cure before adding soil!
Are concrete blocks or cinder blocks safe for gardening?
Fly ash is a common problem when building raised garden beds using pavers, brick or cinder block materials. Fly ash is a masonry additive that contains heavy metals such as radium and arsenic, and is often used in concrete products to improve durability. However, there is little scientific evidence on whether these heavy metals easily leach into the surrounding soil. If you're concerned about this risk, buy the material from a reputable source where you can ask questions and check fly ash specifications.
natural stone bed
In addition to concrete blocks, you can use natural stone such as pebbles, flagstones, boulders, or other foraged rock materials to create durable planting areas. Unlike concrete, there are no chemical additives to worry about here. Natural stone and rocks can be stacked freely, or mortared/glued in place. Since natural rocks are not as uniform in shape and size as concrete blocks, construction required a bit more imagination and fumbling to piece them together. However, the end result will be more rustic, artistic and beautiful - and blend perfectly with the natural garden setting!
Avoid these materials for raised garden beds:
railway connection. While they may look a little odd, railroad ties are treated with creosote -- a "probable" human carcinogen. Creosote may also inhibit or injure nearby growing plants.
Recycled or reclaimed wood of unknown origin. As we've discussed before, be wary if you're not sure about the source, age, or treatment of your wood. It may have been treated, stained or painted to introduce toxins into your garden.
Treated wood, or pressure-treated wood. This is something to discuss with some gardeners. Historically, pressure-treated wood was cured with an arsenic-based compound called chromated copper arsenate (CCA). The bad news is arsenic, which studies have shown can easily leach from treated wood into the surrounding soil. The goal is to make a fairly cheap wood (i.e. pine) last longer in harsh environments. Even though CCA was banned in 2003 and replaced by various less toxic copper-based chemicals, I still personally avoid treated wood. After all, rosewood and cedar actually outlast modern pressure-treated pine
