I have been advised not to use pressure treated lumber to build raised beds, but I just read your idea of lining them with pool plastic. If you did that, could you then use pressure treated lumber, which would at least stop the exterior of the beds disintegrating as quickly?
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Have you considered cedar, and back fill with river rock and landscaping mesh? That would allow the back side of the cedar to breath a bit and (hopefully) give it more longevity.– DA.Mar 28, 2013 at 22:25
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2 Answers
Sure, using pond liner will prevent the copper arsenic from getting in your flowers or food crops right away. However as the wood ages the preservatives will wash into the soil adjacent to your bed. Any plants with spreading roots will take up the preservatives.
The savings in cost for using pressure treated wood are not so great that I would take the chance. Average out the extra cost of using a rot resistant wood over the life of the raised bed and it will not be very much extra.
answered Mar 25, 2013 at 23:12
With or without a plastic lining, pressure treated wood used in garden structures, such as raised beds, poses no significant hazard. This was true even for the old arsenic-containing stuff, which hasn't been available for residential use for over 15 years.
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I've read mixed opinions on this. It would be helpful to see some sources backing this up. May 1, 2020 at 21:52