Using treated lumber for raised beds?


For square foot gardening, I was thinking it might be cheaper to use landscaping timbers that have two flat sides, drill holes near the ends with two of them stacked, and then drive 1 in. EMT conduit into the holes to fix them into position---- like I have seen done with raised flowerbeds. Untreated wood would probably rot in a short time. But what about growing veggies? What are the chances that toxins could get into the vegetables from the lumber if it's treated? Has someone actually tested to see if arsenic leaches out and gets taken into the plants?
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I did square foot gardening for several years but at my age the weeding and work just got to be a bit much. So, I switched to Earthbox http://www.green-trust.org/freebooks/Earthbox.pdf
I'm in south Texas and the heat is extrordinary this year. As a result, when I went to put in the fall plants, the Walmart storage bins I use just crumbled. I went to Tractor Supply Company and bought 6 40 gallon rubber tubs (used to water livestock) and am going to make earthboxes out of them. I'm tellin ya, once you get them built gardening is an absolute joy. It's the ticket for lazy folks like me. All you do is water and replant for the seasons.
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    My ten-year-old raised beds are constructed of approximataely twenty-year-old CCA-treated "landscaping" timbers of the type you describe and my dain bramage is hardly noticeable! Typically, such timbers are dipped but not pressure treated; treated timbers will bear a tag indicating depth of penetraton. Of course, some portion of the arsenic leaches into the soil and _may_ (under specific circumstances) be taken up by vegetables -- root vegetables and potatoes, in particular. Arsenic also occurs naturally in soil and is taken up by veggies. Outside of an agenda-driven popular press, I have not seen a single study definitively establishing a link to human health at the concentrations commonly found. Moderatly-priced soil testing kits exist for the consumer market. The issue of arsenic in garden vegetables is not at all related to that of transference of arsenic from new, unweathered CCA-pressure-treated wood onto the hands and into the mouths of children from treated wood playground equipment.      Bear in mind that neither reason nor empericism has a place among the agenda of the world-changers who depend on strident and persistent FUD to spread their views and to bludgeon society at large into acquiescing. While they may be useful for studying gardening techniques, skills and old-timey lore, I suggest that you view with skepticism "studies" cited in popular publications with "Organic", "Green" or "Mother" in their names: Their POV is implicit and any "conclusions" not to be trusted. You may find this document from the Penn State College of Agricultural Sciences of some help in making your decision:
http://pubs.cas.psu.edu/freepubs/pdfs/uc173.pdf
I direct your attention to the beneficent effects of high levels of organic matter/compost in garden soil and of simply peeling root crops.
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All that said - and thank you for saying it. I used cedar for my food-raised beds. and for the touchy-parts of the kids play centre. Green-Treated wood for the rest. Calculate the cost difference - in my case - not much. Peace-Of-Mind ... priceless. John T.
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    Seconded. The last "child" is twenty years gone from this household and I am of an age that, compared to the levels of toxins deliberately introduced to my body, the consequences of further debilitation from mere arsenic pale. As it happens my "timbers" (nominal 4-inch posts with two opposing flat sides) were "found" some 10-12 years before their incorporation into the garden beds and had spent those years above-ground and exposed to the elements. My beds are fairly narrow; the ends consist of door shimstock ("cedar shingles" to the uniformed) made from "western red cedar" a U.S.A. euphemism for redwood. Were I doing it again and out-of-pocket, I'd probably follow your course closely.
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They use copper napthenate to treat the lumber now, not the copper arsenate they used until about 5 years ago. Copper arsenate was made with - you guessed it - arsenic. Toxicology reports would suggest that the old style was about 12 times as likely to cause problems as the newer ones.
That said, you can always line the wood with something, like plastic, or even sheet metal.
In my case, I simply built my raised bed using concrete blocks, done two blocks high. I lined it with very thick poly film. In retrospect, I think if I had it to do over again, I would probably just buy a bunch of ge silicone II, and apply it with a paintbrush to the inside of the blocks. The blocks are working out pretty well, though.
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wrote:

My understanding is the treating chemicals prevent insect damage but do little if anything to prevent dry rot from constant exposure to moisture.
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I had 2x8" raised beds which I ended up removing & just leaving the bed sort of humped up a little, Thus it was much easier to hoe between the short rows with a narrow weeder. Also if you ever want to use a tiller again, no borders welcome. I turn over my beds at the end of the year or in spring with a spade & it was harder with the frame in place. And there not natural. Dav Dav
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wrote:

I had 2x8" raised beds which I ended up removing & just leaving the bed sort of humped up a little, Thus it was much easier to hoe between the short rows with a narrow weeder. Also if you ever want to use a tiller again, no borders welcome. I turn over my beds at the end of the year or in spring with a spade & it was harder with the frame in place. And there not natural. Dav Dav
================= Why do you turn your beds over, and how deep?
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I am inth eprocess of building some raised beds for next year. I will be using the plastic lumber or Trex, whichever is cheaper. I used Trex whenever it first came out years ago to use as a border instead of that cheap plastic stuff that comes in a roll. It is still as perfect today as it was all those years ago, albeit a little washed out looking since it has been sitting in the sun for years.
This stuff is made from recycled milk jogs and sawdust. You just need to use a few more posts as this stuff bends quite a bit. Once in place, it needs stiffened. On the plus side, you can use it to make all sorts of shapes and such in the garden.

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geronimo wrote:

It depends on the timber. You can get untreated timber that will last 40 years or more in contact with the soil. Talk to you local timber merchant to what is available in your area and the price. OTOH you can use concrete blocks and other building materials that will last in contact with the soil.

I believe such tests have been done but I don't have a link. This is a hot-button issue and all I can say is you should do your own research and be comfortable with the risks you take (or don't take) based on solid information and expert opinion. Such information and opinion may or may not be available here.
David
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