What Kind of Wood Should Be Used for Raised Beds?
Any untreated wood of any kind will work just fine for a raised bed box garden. Some wood like Cedar and Redwood will be more rot-resistant and last longer.
Pine is a favorite because its readily available, inexpensive and easy to work with. Because it is soft, it will not last as long as harder woods like Redwood.
*** Untreated lumber is a must for box gardens containing edibles unless you line the bed with a safe plastic.
Rot Resistant and long lasting woods for Raised Bed Gardens
Some of the harder or denser woods are ideal for raised beds because they are rot-resistant which means they will last a lot longer. Frequent watering will soak the wood causing it to start to decompose or rot. The denser the wood the slower the decomposition or rotting process.
Dense wood and wood like Cedar are desirable because the are insect resistant too. Termites will not eat Cedar. The sap from the Cedar tree is toxic to insects. Cedar makes a great looking raised bed and it smells nice. I use Cedar mulch around by house in the backyard. It significant reduced the cricket population.
Redwood is an awesome wood for raised beds, It is beautiful and very dense but it is also expensive. Redwood will most likely last 15-20 years in a raised bed garden.
Cypress is another excellent wood. It’s very similar to Cedar and is very insect and rot resistant.I love the smell of Cypress lumber. It will last a long time in a raised box garden. It’s not as expensive as redwood. It’s a great choice.
Black Walnut is truly one of the most beautiful grained woods. It makes ideal wood for outdoor projects like a raised box garden. It’s dense, easy to work with and will last a long time outdoors…15+ years
Douglas Fir and Pine are very popular and very inexpensive. These 2 are relatively soft and really easy to work with. You can buy pine boards [2×4, 2×6, 2×8] at any home improvement store and it’s cheap. Douglas Fir and Pine, even thought they are soft, will last as long as other woods, about 10+ years. It’s easy to replace the boards when they are rotted beyond use. I just buy untreated 2 x 4’s at Lowes and use them for the sides, stacked 2 high. They will last 10+ years depending on your climate. If you choose Pine, buy something thick like 2 or 3″. Thick side boards will last a lot longer than a 1″ thick board.
Hemlock is another soft wood like Pine and is available in a 2 x 4 configuration at most home improvement stores. It’s pretty inexpensive too.
Spruce is a fantastic wood for raised beds. Spruce is the strongest wood for 2 x 4’s that you can buy. It is typically sawed for outdoor furniture since it is rot-resistant and very strong. You can buy Spruce 2 x 4’s at any home improvement store and they are the straightest 2 x 4 you will see. Spruce is less expensive than Cedar and has the same preferable qualities.
Juniper (rustic-looking) is another fantastic wood for raised beds. It is long lasting, beautiful and chemical free. Juniper is even longer lasting than Cedar and Redwood. Juniper can last last up to 50 years in contact with the ground because it has a high level of oil in it’s sap. Juniper is the best wood for longevity for outdoor projects. It comes in the following sizes at lumber yards; 2×6 and 2×8. Both of these sizes are great for a raised bed.
American Chestnut would be a great wood but it’s availability is limited to reclaimed wood. You never know what you’re getting with reclaimed wood or boards. Go with juniper instead.
Yew is a good choice but I’m not sure about its availability. It’s very good at rot-resistance and also insects attacks.
Catalpa is another wood that is pretty rot resistant even in contact with soil. It is also easy to work with. Catalpa can be a little pricey though. I have seen it priced from $2.50 – $12.40 per board foot.
Dense Woods for Raised Beds
Black Locust is very dense and very durable for outdoor applications. It is the strongest and stiffest domestic lumber. It is primarily used for outside decking. It is very similar to Hickory.
White Oak is a light colored wood that is very durable regarding rot resistance. It is most commonly used for boat building. It is easy to work with using power or hand tools. The cost of White Oak is moderate and comes in common sizes and lengths.
What About Plywood?
Plywood would not be a good choice since it is made from laminating or gluing thin sheets of wood together. The glue that is used to laminate the wood sheets will eventually dissolve after several waterings. Avoid laminated woods.
Wood to Avoid
Reclaimed or recycled wood is not a good choice unless you know the history. If you are not 100% sure of the history, avoid reclaimed or recycled wood. I like to just avoid it since there are much better choices.
CCA Pressure Treated Wood is a NO. I would recommend to NEVER use pressure treated wood for a garden in which you plan on growing edible plants or fruit. It’s just too risky. There are better choices.
Wood Alternatives That Are Safe
There are some good wood alternatives if you are against using wood.
Natural Rocks are a great wood alternative and are very safe. You can get them in brick form to make it easier to stack them. They are relatively inexpensive and will last forever. Granite, sandstone, quartz, slate and clay are good choices. I have read that bricks are fine to use also. Bricks are cheap and very durable and look great.
Concrete Blocks are OK to use but may leach lime into the soil of the raised bed. You’ll need to monitor the PH if you want to use concrete. Concrete blocks are easy to use since they are square and stack-able.
Avoid These Materials For Raised Beds
Cinder Blocks can be made with Fly Ash which is a byproduct from the Coal Industry. Since Coal contains heavy metals and other substances which are toxic, you don’t what any product that comes from Coal in your garden. Some Cinder blocks have Fly Ash and some may not but it’s not worth second guessing. Don’t use Cinder Blocks for a garden.
Railway Ties are not suitable for a garden. They are treated with chemicals to prevent rot. Creosote and CCA have been used to treat Railroad Ties. Both treatments are toxic.
Tires are full of hazardous chemicals. I don’t recommend them for raised bed gardens.
Paints, stains and finishes – beware of these. Most are hazardous. Some may be safe but why risk it when they are much more suitable materials available like bare wood.