Is it OK To Use Treated Lumber? (Part 1)

The price of lumber is increasing, so is it time to start thinking about treated lumber for raised bed construction?

All the beds in my garden are bordered with either wood or rocks. The wooden beds are made of lumber or logs, and due to price and availability where I live, the wood is almost always spruce. I have about 24 raised beds that are made of wood, and I find that untreated spruce last about 7 years (give or take depending on thickness) before becoming so rotten that it falls apart.

The raised bed in this picture, taken in 2016, not longer exists, and is currently turning back into soil in various locations throughout my garden!

Most of the beds made from lumber use untreated spruce 2”x6” boards, and are 4’x8’ in dimension; such that three 2”x6”x8’ boards are required to make a bed. When I bought my first home in 2004, a spruce 2”x6”x8’ was about $2, or even less sometimes if I could find rough cut boards or boards called “seconds” that are slightly damaged, but fine for things like raised beds.

Currently, untreated spruce 2”x6”x8’ go for about $7 each, which is 3.5 times what they used to cost about 20 years ago. Sadly, I do not make 3.5 times what I used to make 20 years ago (nor do most people I would imagine), so the rising price of lumber is a concern, because whereas a single raised bed used to cost about $6 or less to slap together, the cost is now $21. If we extend that cost to the replacement of all 24 of my wooden beds, the cost runs to $504, and that’s not counting the 3” screws I use to assemble them, which are also getting more expensive each year¹.

Being cost-averse by nature, I have been considering alternative materials for beds, one of which is pressure treated lumber. Many gardeners are wary of using this material in a vegetable garden due to the risk is toxic chemicals being leached into the soil and being taking up by plants intended for consumption, so I thought I would explore this option in depth.