Appropriate Materials for Building Raised Beds

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You can make raised beds from such common materials as concrete blocks, bricks, railroad ties, pressure treated lumber, etc. Railroad ties need to be completely dry before using, as leaking creosote can affect your plants. Pressure-treated lumber may be unsafe for use in the garden if treated with such chemicals as pentachlorophenol. Be safe and aware of the hazards of using treated wood in the garden.

Kits are available so that you can easily build your own raised bed from beautiful hardwoods like cedar. You can also buy kits that are made from polyethylene blocks that look like natural stone and work pretty well.

You can find a complete selection of raised bed gardening kits at Clean Air Gardening.

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  1. I have been growing in a raised bed constructed from pressure treated 2×6 lumber. Before filling the bed with soil, I lined the inside face of the lumber with 8″ of aluminum flashing (with the extra 2″ going down below the lumber, into the soil), thereby keeping the growing soil from coming into contact with the lumber. Is this sufficient to protect the crops from any chemical that would leach from the pressure treated wood? (the lumber was purchased 2-3 years ago and the bed was constructed from this wood last spring).

    I’m about to add additional beds this spring using the same method and materials – any comments or suggestions?

    Thanks, Jim

    • @jim wight-waltman,

      Yes, I would think what you described would be sufficient.

      These days they don’t pressure treat wood with arsenic based products anymore. And frankly, the amount of leeching that the wood might do is probably not a huge deal.

      My parents used to have a raised bed garden with railroad ties, which is definitely on the AVOID list. The plants still grew, and no one got sick.

      I’m pretty casual about that kind of thing. But if someone is worried about it even slightly, it’s better to just take a few extra steps like you did, so that you can garden without having to worry about it.

      • I did some research on this a while back. The only real danger from arsenic-treated lumber (which, as you correctly stated, is no longer marketed) is from eating poorly-cleaned root crops. Even then, the danger is so minimal as to be non-existent. If I recall correctly, one would need to eat multiple-pounds of contaminated dirt (not vegetables, the dirt itself) to even show an effect from the arsenic.

        • @Rob

          Thanks for your comment.

          I pretty much agree with you. I think it’s something that you should avoid if you can, but it probably isn’t worth worrying about if you already have your raised bed set up that way. It’s sort of like using railroad ties, which have similar issues even though people have used those for years and years as basic raised beds.

  2. I had 16 raised vegetable bed on my farm in southern Indiana—all made of used cross ties. All the veggies grew fine, and nobody got sick. I think the key is OLD, not new. The basic bed used 5 ties (one cut in half for the ends) for 16x 4. That, plus my mighty Mantis tiller, kept me going for more than 10 years.

    • @Lorraine,

      Yes, I agree with you in theory. My parents also grew a vegetable garden with railroad ties for many years with no ill effects.

      But in general, if you are starting your garden and you have a choice of materials, it’s easier to just avoid railroad ties rather than trying to figure out if they are old or new. So that’s why I recommend not using them at all.