I like raised beds. They can take some time to set up, but are pretty, functional, and help you work around bad soil.
The best wood for a raised bed is thick, untreated, solid lumber. 2×10 or 4×4 standard pine lumber from the store is the best choice for the environment, and your garden. It can last 10 years, doesn’t harm soil life, and is cheap to buy.
After years of research and trial and error, that’s my official answer. Basically for me, it comes down to healthy soil life and practicality. There are other options that you may like more. Keep reading.
Super simple plans for a raised bed at the bottom of this article!
What Wood Works for a Raised Bed?
The most common wood used in raised bed gardens is pressure-treated pine 4×4 or 2×6 boards. They certainly work. I mean, it will hold the dirt in and last a long time. Pressure-treated lumber can last 40 or 50 years in a raised bed. But, there are some serious concerns about those long-lasting chemicals.
One of the most commonly recommended options is cedar boards. Cedar is available at any lumber yard and most home improvement stores. It’s naturally rot-resistant, and some cedars will outlast any treated lumber by far.
My grandfather lived on the Torch River in northern Michigan. There used to be big, cedar posts in the water in front of his house where the ferry would tie up 90 years prior. One day he went out in the river, pulled them out, and split them for firewood. Ceder lasts a long time. But, it’s expensive.
There are other woods used, like yew and locust, but those are specialty woods and are both expensive and hard to get. Unless you are cutting your own, I really don’t suggest either of them. They are rot-resistant, just not very common, and not at all practical for most people.
If you are fortunate enough to have an Amish lumber mill nearby (there are several in my area) you have plenty of good options. They buy and mill all kinds of local wood, and usually sell it way cheaper than anyone else can. That’s a great place to get some really stout, thick, hardwood lumber for cheap.
When it comes to lumber, denser wood lasts longer. Oak lasts longer than maple, which lasts longer than pine. The cedars and junipers are lightweight and last forever, but those are the exception. The issue with dense woods like oak, hickory, or walnut is that they are super expensive from a regular lumber yard.
There are a lot of options that look good until we consider price and availability. That’s what sets the winners apart from the losers in my mind. All that brings me back to basic old common lumber, pine.
Cheapest Wood for Raised Beds
Basic pine lumber is the cheapest wood for a raised bed garden. 2-inch pine boards are the affordable option for a sturdy raised bed and will last at least 5-10 years, depending on humidity. 2×10-inch pine boards (regular lumber from the store) will build a decent, chemical-free raised bed.
You can’t get any cheaper wood in the US than pine. It’s farmed and harvested from national land in great mass. It’s also super easy to cut and mill, is lightweight so shipping is less, and it’s plenty strong for building things. No, it’s not rot-resistant but that’s okay.
See, we’re not building a house here. Yes, basic pine lumber will break down when exposed to outside conditions and ground contact. The good thing is that it doesn’t take a lot of strength to hold in 10 or 12 inches of dirt. If you want a shorter bed, up to a foot tall, just use basic pine lumber. It works.
There are 2 things I like about pine. First off, it’s cheap. Second, it’s not leaching chemicals that hurt soil biology like treated woods. Also, you can buy it from any home improvement store or lumber yard. Okay, that’s three things. I guess there’s one more still.
Pine does eventually break down to the point of not working anymore. That’s a natural process that means your soil is working. When it does need replacing, take the old wood and bury it deep (at least 2 feet) under your raised bed so it continues to feed the soil like a Huglekultur bed.
Now that’s a way to build up your soil!
What Wood Lasts the Longest?
Cedar is generally the longest-lasting wood for a raised bed. Juniper and cypress are also long-lasting woods but are harder to find in a store. These woods are naturally rot-resistant but can break and split if you are hard on them. True cedar is quite soft, but juniper and cypress are fairly sturdy.
If you happen to have any of those trees on your property, you can cut logs to line a raised bed. Locust (all varieties) is another tree that’s naturally rot-resistant and will work very well. You can border a bed with logs. Stacking and stacking together several smaller ones together work well too.
Either way, I want you to forget about treated lumber and look at chemical-free options. The additives in treated woods inhibit rot by killing microbes. Microbes are what cause soil to work. Stop destroying the health of living soil and work to build up the soil life beneath your feet.
How Long Will Untreated Wood Last?
Untreated wood should last 10 years in average conditions and a minimum of five years in extreme conditions. Thicker wood will last longer than thinner wood. Hardwood logs will last 2-4 times as long as regular boards.
If you have a dry area, 2-inch pine lumber can last well over 10 years in the garden. In my area, it’s about 5-7 years. We get a lot of rain. Areas with more moisture will break down wood faster than drier areas.
I know a lot of people will balk at the idea of rebuilding a raised bed every 5 years. But it’s once every 5 years, and it only takes a few hours at most. Buy a few boards, cut them, and nail the corners together. you don’t have to level the ground and re-fill it every time, just replace the shell.
Currently, the cost of a 10-inch tall, 3×10-foot raised bed with basic lumber is under a hundred bucks. If you built it from cedar, that’s just over 200 dollars. And that’s 3/4-inch cedar, which will split and crack very easily. The startup cost is much lower with regular old pine. Pine works.
How Thick of Wood Should I Use?
I’m a big fan of 2-inch lumber. Finished 2-inch lumber is actually 1-1/2 inches wide. That’s the stuff I’m talking about. Regular old 2-inch wide lumber from Home Depot. Since we’re using untreated lumber, and cedar is expensive and fragile, 2-inch pine is a good option.
I’ve used 1-inch board and it worked for a couple of years. I also used 1×6-inch cedar, which split in half by the 6th year. Hence, not a fan of cedar. If you want a bed that’s 6-inches or taller (read How Deep Should a Raised Bed Be) I recommend 2-inch thick lumber, at least.
Is Treated Wood Okay for Raised Beds?
Treated wood causes some environmental concern and is not allowed near an organic growing environment. While not as bad as it used to be, it still leaches toxins and heavy metals into the soil, which hurts the soil life.
Wood treated with arsenic is not allowed in the US for “home use” materials. You can still get it, and many wood products from China have been found to have arsenic. But, if you buy treated wood at the store, it doesn’t have arsenic. What does it have then?
Pretty much all treated woods have one or more of various compounds, plus a heavy dose of copper. Copper sulfate is pretty common. Sounds harmless enough. But, copper is actually quite hard on the environment. Copper kills the fungus, bacteria, amoebas, and bugs that make soil work.
So, the natural ability of the soil to regulate itself, improve itself, and break down organic matter will be greatly impacted if you use copper-treated lumber. I used to have a little copper-treated wood here at Cairnstone Farm. I’ve gotten rid of everything except my front porch. I simply won’t hurt the environment anymore.
The safest material for a raised bed is untreated wood. Even brick and concrete can contain chemicals and petroleum compounds that you don’t want in your garden.
Plans for a Simple, 3×10 Raised Bed.
- Buy three 2×10 pine boards.
- Cut two 3-foot pieces off one of them.
- Now, prop up the 10 footers and 3 footers to make a nice rectangle.
- Using 4-inch nails or outdoor screws, secure the corners together. Use 4 nails or screws per corner
- Take the remaining piece and cut it into four 12-inch pieces.
- Nail or screw the 12-inch pieces across the top of each corner as a brace to help hold it together.