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Want to know the best wood for raised garden beds? Raised beds are garden containers, commonly made from wood, and the type of wood we use will determine how long-lasting, safe, and sustainable they are.
If you are looking for designs, I have free plans for building raised garden beds here .
Choosing Wood for Raised Beds
You’ve got perfect soil, a level yard, consistent rainfall,and everything grows beautifully, right?
Ok. No.
Every garden has challenges and raised beds can resolve many of them.
Bad soil, a sloping yard, and tree roots are all reasons to grow in raised garden boxes.
A raised growing space is also better for back and knee problems.
But what kind of wood should you use? Are some types of wood harmful for the garden?
Wood is a popular choice for building plant boxes because it’s fairly inexpensive, readily available, and lasts quite a few years. But you do have to choose carefully to avoid contaminating the soil and ensure your choice is eco-friendly source, affordable, and long-lasting.
So, unless you live in termite territory, it’s time to go wood shopping.
Contents
- What is the Best Wood for Raised Garden Beds?
- What to Consider
- FSC Certified
- Safety
- What to Consider
- Wood Options
- Wood to Avoid
- Wood Alternatives for Building Raised Beds
- Resources
What is the Best Wood for Raised Garden Beds?
Here are the key traits to look for, then we’ll explore the details.
- Locally-sourced & Sustainable
- Safe for soil/food crops
- FSC-certified
- Rot–resistant / Long-Lasting
For me, locally-sourced, FSC-certified, untreated, rot-resistant wood makes the most sense. But it is not always possible to check all these boxes.
I currently use 1-inch untreated pine boards because they are readily available in my area. The wood gets a lovely, rustic barn board patina but lasts for many years in my Canadian climate.
I also use some pressure-treated wood for various garden structures including large raised beds.
The wood that people worry about leaching ‘chemicals’ into the soil is CCA (Chromated copper arsenate) pressure-treated wood or old railway ties. This type of treated wood was banned years ago for household use. You can read more about it below.
Keep in mind that wood selections vary greatly by region.I admit the suggestions(below) are quite idealistic, but why not do what’s best for the health of your garden and the environment if you can?
What to Consider
1Local & Sustainable
The best choice (and often the lowest cost) is locally-sourced wood coming from sustainably-managed tree farms (as opposed to decimating old-growth forest by clear-cutting).
2FSC Certified
If you can, use wood withFSC (Forest Stewardship Council)certification. The FSCis an international,not for-profit organization that promotes the responsible management of forests.
3Safety Considerations
Treated Lumber
If you want to use treated lumber, do your homework first so you’re certain it’s safe for yourfood garden.
Safety standards and regulations vary by region. I notice some manufacturers now specifically mention if they consider their treated wood safe for vegetable gardens, where they used to just mention use for fence posts and decks. It’s up to you to do some research to decide if you trust them.
What goes in your soil goes in the water, plants, and wildlife, so it’s important to be careful.
Some Current Wood Treatment Methods:
- Alkaline Copper Quaternary (ACQ)
- Copper Azole (CA)
- Micronized Copper Quaternary (MCQ)
- Sodium Borate (SBX)
Tip: Consider Using a Liner
To be cautious, some gardeners line their treated wood beds with aprotective layer of plasticto form a barrier between the wood and soil. Again, you will need to research the plastic to ensure it is food safe and consider the effects of condensation forming between the plastic and the wood.
4Durability and Rot-Resistance
How long any wood lastswill depend entirely on the type of wood and local conditions.
My current raised beds are made from 1-inch untreated pine and last approximately 10 years. But I also live somewhere where therain is moderate and drainage is very good.
If your raised beds will be exposed to a lot of moisture, wood like pine may only last a few years. Wood borers like termites are also a possible concern.
Other naturally rot-resistant woods (listed below) will last even longer.
Should raised beds be sealed (water-tight)?
Opinions are mixed on whether wooden raised garden beds should be sealed with caulking or sealant to try and make them water tight. While it may extend the life of the wood, there is always the risk that water sits in the container longer, gradually causing rot.
Wood Options
Check before you buy to be sure the wood meets your criteria. Here’s a few popular ones:
Naturally Rot-Resistant and Long-Lasting
- Cedar
- Juniper (rustic-looking)
- Redwood
- Yew
- Catalpa
- Chestnut
- Cypress
- Douglas fir
- Hemlock
- Pine
- Spruce
Dense Woods
- Black locust
- Black walnut
- White oak
Check your local lumber yard for more ideas.
Wood to Avoid
Do your research first to confirm you are comfortable with the exact product you are using.
Be Cautious
- Recycled or reclaimed wood if you do not know the originor wood that has beenstained or painted. Older paints with lead are a big concern.
- Older (CCA) pressure-treated wood, which is banned in several countries. ACQ (Alkaline Copper Quaternary) lumber is a better alternative.
Do not useCCA (Chromated copper arsenate) pressure-treated wood or old railway ties. This method of preserving wood was voluntarily discontinued in the production of residential woods in the United States (2003) and Canada (2004), but it is still used for industrial purposes. The concern isarsenateleaching into the soil and uptake by plants. As thrifty gardeners, we like to repurpose wood that seems to be in good condition, but this is not an option with old, treated wood.
Read more:
- Staying Safe Around Treated Wood| Government of Canada
Wood Alternatives for Building Raised Beds
As with any building materials, you must do your own research to make sure the choices you make are safe, eco-friendly, sustainable, and right for your situation.
These are ideas to research further, not recommendations.
- Recycled composite plastic lumber
- Composite lumber—made from recycled wood shavings.
- Concrete, concrete blocks or bricks—can get quite hot in the sun, but lot of people use them with good results; do not use cinder blocks (the older version of concrete blocks).
- Rocks
- Metal stock tanks or raised beds, galvanized metal—may heat the soil too much; some research indicates galvanized steel can leach excessive amounts of zinc into the soil; can rust over time.
- Felled logs
- Old doors—cut lengthwise – be cautious with anypaints or stains.
- Shutters—be cautious with any paints or stains.
- Straw bales
Avoid
Cinder Blocks Versus Concrete Blocks
Cinder blocks (popular many years ago) are made from fly ash and contain heavy metals. These are not considered safe for gardens.
Concrete blocks are generally considered fine but always check what the product is made from to be sure.
These all have safety concerns:
- Cinder blocks
- Railway ties | Creosote-soaked ones are not safe.
- Tires | I know this is fairly popular but I am not convinced it is a soil-safe idea.
- Paints, stains, finishes | Check with the manufacturer first.
Resources
Free Tip Sheet
Empress of Dirt
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DIY Raised Bed with Privacy Walls
Also see DIY Raised Garden Bed With Built-In Privacy Wall.
Frugal Building Tip
- Design your raised bed based on available lumber sizes to minimize waste cuts.
I like to use 8-foot lengths to create easy-to-assemble 4×8-foot boxes but also keep in mind what fits your body size for easy reaching.
Free Building Plans
- Free Plans for Building Raised Garden Beds
- Alsocheck your local library.
Save on Soil
- Tall raised beds hold a lot of soil and that can be expensive. Use these tips for alternate ways to fill a raised bed without spending a fortune.
Recommended Book
- The Raised Bed Revolution by Tara Nolan
As always, when making garden decisions, consider the effect on the soil, water, air, and wildlife.
~Melissa the Empress of Dirt ♛
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