Raised Beds

[headfullofbees]

The question arises from time to time, about safe ways to preserve the wood in raised beds, given that they are, when in use, subject to damp and various fungi.

I regret that it's taken so long to come up with what I reckon is a good solution that I haven't previously heard of.

Wiping the boards with a cloth soaked in RAW linseed oil, & allowing them to dry, twice, prior to installation, should harden & preserve them for a number of years.
This is how cricket bats are given their strength; white willow is a softish wood which will dent badly when striking a cricket ball, but a couple of layers of linseed oil, & it's water off a duck's back.
Linseed oil is non toxic, so even if some should leach into the soil, which I doubt would happen, it would be perfectly safe for humans, pets % bees.

 

[lifegardener]

Hemlock, Cedar and Redwood are good woods for raised beds.

 

[DirtMechanic]

Personally I have become enamored with LP smartpanel, a modern engineered osb using boric acid as a preservative. Even then I would line wood. A paint version would work, or a tile under layerment sealer like redgard or even sheet plastic but I think sheet plastic would be the first to oxidize and fail. I have had a piece of smartpanel siding laying on wet leaves outside my shed for since I built the shed at least 5 years ago now. Primed on one side, the piece is remarkable for an osb product. I have zinc studs out there that have rusted in shorter time.

 

[Marck]

Another easy and rot-resilient raised bed method is to build a rectangular bed out of cinderblocks. No need to mortar, just partly mound soil around the outside of the bed to brace the blocks. You should put the cinderblocks with hollow sides facing upwards. This gives you extra spaces to use as cubbyhole planters for herbs and other smaller annuals, perennials, and vegetables. It's a fun idea. I've built several for my succulents and geophytes.

 

[Mr_Yan]

I build my raised beds using a galvanized corrugated roofing panel. I orient the panels such that the corrugations run vertically and sink the bottom of the panels into the soil a few inches. The tops are framed out with a 2x3 and I use a deck stain / sealer on that but it is not in contact with the soil. I plan on building two more tomorrow and will post more pics.

BUT:
There is no evidence that modern ACQ treated lumber will leach into soil or impart anything into veg grown near it. This is not the old arsenic treated stuff but an alkaline copper solution.

 

[LouisFerdinand]

I do yard work in a neighborhood where Alexander across the street has planted some vegetables in cinderblocks.