Using old pressure treated wood for vegetable garden?

Discussion in 'Fruit and Vegetable Gardening' started by zenshack, Feb 8, 2010.

  1. zenshack

    zenshack Active Member

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    Hi,

    I wanted to get some opinions on this.

    I have a stack of old pressure treated 2x4's that I was thinking of building a raised vegetable garden with. These planks were originally part of my neighbours deck for almost 30 years and have spent the last few months in my garage drying out.

    How much of a threat is there of any remaining chemicals in this old wood leaching into my garden soil. Will lining it with plastic help? What do you suggest?

    Thanks
     
  2. Ron B

    Ron B Paragon of Plants 10 Years

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    Depends on what they were treated with.
     
  3. zenshack

    zenshack Active Member

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    Because of it's age I assume it is the older version of pressure treated wood no longer sold, CCA.

    As for what it was treated with I imagine over the years it has been re-stained/ oiled a few times, but with what exactly I do not know. I'm sure it has been at least 5 years if not longer that anything was applied, the 2x4's are very grey and weathered.

    What about using heavy weed blocking plastic to line the inside of the box (Not the bottom)? Would that make things potentially better or worse?
     
  4. Ron B

    Ron B Paragon of Plants 10 Years

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  5. zenshack

    zenshack Active Member

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    What about using very old (30 years), used(as a deck), and weathered PTW, considering this wood leaches the most in the first rainy season or two?
     
  6. Blue Fox

    Blue Fox Member

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    Pressure treated lumber is toxic! I don't use it at all, under any circumstances, and you can't even safely dispose of it.
     
  7. cowboy

    cowboy Active Member

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    Here's an article about CCA usage. Since you will be putting these with the 1-1/2" edge into the bed, I would think that this part has not been stained but has been subjected to 30 years of leaching.

    The big issue with CCA was the arsenic and children's exposure to it from playground equipment. It cannot be that bad since the CCA playground equipment down the street is less than 20 years old and it's still in use. The city hasn't seen fit to paint it nor replace it. And yes, my grand children are allowed to play there.

    Personally I would have no issue using the wood. You can plant flowers next to the edge of the box and keep the veggies away from any possible contamination. Better to use the wood than put it in the landfill.
     
  8. pgamalo

    pgamalo Member

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    The first garden I started 30 years ago used the old CCA green pressure treated wood.
    At the time,i used 2 by 8 to form a bed(not raised).
    The boards themselves were a couple of years old but still had a greenish tinge.
    I never had any problems with anything I grew in these beds.I am 66 now,and I still use the same method and still no problems.
    I think that the scare of chemicals leaching into the soil was vastly blown up.

    Phil in Buckingham
     
  9. cowboy

    cowboy Active Member

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    We have been subjected for the last 60 years or so to the fraud of the Linear No Threshold (LNT) model for toxic dose exposure and its companion the "precautionary principle." The LNT model says that no level of exposure to toxins is safe. This was a change from the threshold dose model that allowed for exposure to small doses of things. Exposure was tolerable up to a threshold level but in larger doses could be harmful. Dr. Edward Calabrese has a good article on this issue and its history.

    http://www.galileomovement.com.au/docs/Calabrese-Muller-1.pdf

    A third and even more interesting dose response model is the hormetic model. This model indicates that exposure to low levels of some toxins have a positive affect on human health. Low level radiation exposure has shown to reduce cancer rates as opposed to increase cancer rates.

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2477708/

    Dr. Calabrese talks about hormesis and the other models in this video.

    http://www.youtube.com/watch?v=fokmHSukJ1Y


    I would be comfortable to use 30 year old or even new CCA preserved wood in vegetable production. In fact I use old CCA wood as the floor of my compost bins (Rats can't get into a compost bin with a raised floor). The amount of compost in a cubic metre that will have been in contact with the CCA wood is very small. How much arsenic is taken up? Probably not very much. Once that compost is spread and mixed into the soil, not very much arsenic will be taken up by the plants. Let alone what would end up in the edible parts. My body can easily handle that. The problem with the LNT model is that the "precautionary principle" is invoke and common sense goes out the door.
     
  10. Lysichiton

    Lysichiton Active Member

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    All my beds over the years have used pressure treated lumber. My house is covered in the CCA treated siding. I have lived here for 35 years, raised three kids, lots of various pets & never seen ill effects. I don't think there is much migration of the chemicals in a suburban setting, or even a great quantity. Squirrels have chewed on it (My kids didn't, nor do I) - I hoped they would be poisoned, but no such luck. I observed that moss did not grow in the 2-3 inches adjacent to my foundation for 20 years or so. I am on sandy soil, so there is no surface runoff to contaminate.

    I gave up worrying. My present beds are recently built and raised using 2x10 PT cedar. The main effect is that I don't get much trouble with slugs and snails, who don't seem inclined to brave the lumber to get into the beds...Yippee!
     
  11. Durgan

    Durgan Contributor 10 Years

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    I used old railway creosote treated railway ties to line my garden beds. I lined them with plastic bags. Eventually due to being unsightly I removed the bags. Th following Spring upon digging along the ties I discovered many and I mean many very healthy earthworms. They were all lined up along the ties. So much for the caveats.
     

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