Raised Bed Materials
Note: Missed a few days there, this last week has been very hectic. Tis the season after all.
Winter fast approaches here in zone 6b, and with that the garden beds get some well deserved rest. Well, except for the brassica bed which is still going strong. Now my thoughts turn to next year’s garden and all that entails. A new year means new plants, new plants means new and/or replenished dirt, and new dirt means new raised beds since I can’t know for certain how big the fire pit / trash pile buried in the middle of my back yard is.
That was a fun thing to find by the way. There I was, double digging planting holes for my three new apple trees, when I started uncovering broken glass and bits of rusted out dinnerware and cans. And ash, lots and lots of ash. Likely a fire pit then, but for all I know the first structure on this property could have burned down eighty years ago and they simply bulldozed the remains, piled new topsoil over it, and started building anew. Thankfully I prefer raised garden beds so had already built out ten of them for the 2022 garden and everything went fine there from a plant health and nutrient standpoint. Double digging is hard work, coincidentally.
With the removal of our large oak tree in the backyard I now have roughly twice the open space to play with, and that means new garden beds. I am going to try growing a bed of asparagus, and I’d really like some taller beds for planting strawberries in so that I don’t have to crawl around on the ground to harvest them. Right there is three new beds at a minimum. I’d also like to try a bed of sweet potatoes, though that may be a year or so out. We’ll see. Regardless, since I’m thinking of these new beds I thought that now might be a great time to discuss raised bed materials, their uses, pro’s/con’s, and my plans.
Let’s start with what is likely the most common material, if not the trendiest: Wood
Using lumber involves making a few choices, namely whether or not to use cedar and whether or not to go with treated lumber. Cedar is, at least when used as a siding material, more resistant to degradation due to moisture. Some folks swear by it for their garden beds on the basis that the beds themselves last several years longer. Here in Ohio cedar is somewhat hard to come by affordably and I’ve heard mixed reviews from folks who’ve used it, if it makes a difference it may be specifically better in different climates But I can’t verify that because I didn’t go with cedar. Let me know in the comments if you used cedar and if you would use it again.
Treated lumber versus untreated lumber is sort of a similar deal, treated lumber (pressure treated specifically) lasts longer in contact with moisture. Some folks worry about whether or not the treated lumber is safe to use due to the chemicals involved, as long as your pressure treated lumber was manufactured after 2003 it is considered safe by the EPA. Prior to 2003 pressure treated wood was treated with chromated copper arsenate; you may have noticed the common root word in arsenate and arsenic which isn’t a coincidence. On the other hand folks have been building garden beds out of pressure treated wood for decades and there weren’t exactly tons of problems so the threat that the presence of chromated copper arsenate posed is a bit poorly understood. Since we’re discussing wood: never use railroad ties, they are treated with much more dangerous preservatives. With the current wood costs I’m not sure that going with treated makes a whole lot of sense, especially if you don’t mind rebuilding the beds in five to seven years. Pressure treated lumber is supposed to make them last a couple of years longer, and cedar a few more years on top of that.
Wood beds are nice because you can customize the shape and sizing far more than any other material. Wood is one of the cheapest of the materials as well (when buying new) but not by as large of a margin as you might think, this is likely due to the post-covid-lockdown lumber and housing markets. Since the housing market is currently staring down the barrel of a sharp downturn lumber prices may fall, making wood a more attractive option. Wood is the among the best materials to use for a tall raised bed, with tall being more than 12” or so, but expect it to cost more in this application. For my 2022 garden, which was the first year of gardening at the new house, I spent roughly $90 USD / garden bed using untreated lumber, and that was after weeks of shopping for the cheapest prices I could find. While wood is the second cheapest option for constructing a raised bed I wouldn’t say that it’s a cheap option overall. Drawbacks of wood are as follows: deteriorates the quickest, second heaviest material to build with, long board lengths prone to twisting and warping at 12” wide board size, second most difficult material to build with due to weight and tool requirements and twisted/warped boards. I used untreated lumber in 2022, I likely won’t be using it again.
Next up: Concrete Blocks
For a raised bed that is short (12” tall or less) cement blocks are a pretty good way to go provided that you aren’t planning on mortaring them together. For my 2020 and 2021 garden I went with concrete blocks at roughly two feet tall, which required mortaring, and from that experience I can confidently say that I’m no mason and that I will never ever do that again. It worked well, but the construction was such an arduous task that it just isn’t worth it. Besides, mortared concrete blocks aren’t the best material to use in contact with wet dirt which freezes yearly, lots of cracking and spalling. In an application where the block layer is just a single block deep though with no mortar between them I think this can make for an excellent material regardless of the climate that you’re in, if a block cracks in half due to freezing just replace it for less than $2 USD. Concrete blocks are a bit like wood in the sense that you can customize the size and shape of the garden bed fairly easily, and overall concrete blocks tend to be pretty cheap, a 10’x4’x8” bed will run you about $45 USD in total and requires no tools. Concrete blocks in a drier climate will last pretty much indefinitely, so for a long term affordable option cement blocks are a decent choice, just mind your shins because the corners of concrete blocks are rather unforgiving.
While the work involved in constructing raised bed from concrete blocks isn’t intricate and requires no tools (unless you are mortaring, that’s a whole different can of worms) it is the most physical, each 16” long block weighs roughly 27 lbs and the bed mentioned above would require approximately twenty of them as well as two half sized blocks. If you are building more than a couple of raised beds be prepared for quite a bit of heavy lifting and quite a few trips back and forth to the store. Mortaring is both an art form and a science, I can’t recommend using concrete blocks taller than a single block layer in good conscience since a bag of mortar is another 80 lbs, each bed is likely going to take at least two bags, and mixing mortar is a skill that requires mastering to get decent results and requires some tools.
Plastic Beds
I’ve never used plastic raised garden beds, they aren’t exactly great for the environment and aren’t likely as sturdy as some of the other options. What they lack in sturdiness they make up for in being lightweight and easy to assemble. From a cost perspective they’re roughly twice the price of a similar sized bed in wood. They do come in white and will never lose their color, so if you are going for that English garden aesthetic this could be a good choice. Also, the material holds up better to being hit by a weedwhacker than painted metal does so that’s a plus. Plastic in general is pretty durable as a material provided that it’s one of the UV resistant types.
Metal Beds: The currently trendy choice
If you follow any gardening Youtube channels you’ve likely seen them, tall raised beds in an odd mix of seafoam and olive green. While that’s a specific brand (Birdies) there’s a bunch of variations available. I even have one, though it’s not a Birdies bed and it’s only 12” tall. The biggest drawback to a metal bed is the cost, with metal beds falling within a sort of similar price range as plastic. The coating on metal beds don’t hold up particularly well to weedwhackers, which I know from experience. While the coating of a metal bed isn’t as durable to impacts as literally any of the other options metal beds have quite a few good features. They are lightweight. They are somewhat easy to assemble, and assembly generally requires only a screwdriver. They are extremely resistant to the effects of the weather and climate, though not as much as plastic; a metal bed will last upwards of twenty years. Metal beds are the only material that I would go with for a bed taller than 12” as well due to the ease of construction and durability, really thick wood (I’ve seen good results with painted and stacked 4”x4”s) also makes for a good construction material for this sort of bed but won’t be anywhere as easy to assemble, will cost three times more, and good luck adjusting it’s position without quite a lot of help.
My plans for the 2023 garden beds? Well, I don’t want to have to bend over and muck about with strawberry plants, I’d rather stand and muck about with strawberry plants, and asparagus is a fern that is pretty short when harvested. For my purposes I want some tall raised beds, I don’t want to go with concrete blocks, and wood looks nice but is way too much money in this application. That leaves me with metal beds as the obvious choice. I may go with a set of Birdies beds, or maybe Vego, not sure which brand yet as I’m still researching. Vego is available via Amazon, Birdies is available here in the US via Epic Gardening.