I was on a gardening forum recently when a women posted that she wanted to grow an organic garden in raised beds built out of cedar. Her husband balked at the cost of cedar and shorter-lifespan of untreated pine. He wanted to use treated lumber. When I said I didn't understand using treated lumber in an organic garden, another poster didn't understand why anyone would pay 8x the price for a garden...why bother gardening at that point.
For decades pressure treated lumber was...well, treated...with chromated copper arsenate as a preservative. Everyone thought this was the answer to all our problems...until research came out that arsenic leached into the soil. Now, some studies said that there wasn't horizontal leaching (meaning, only the contact area near the wood was contaminated...not 20 feet away), others said there was more of an issue. As far as I can tell, both sides agree that the soil is containmented for a very, very long time. There was also some debate over how much arsenic the veggies absorbed and whether or not repeated ingestion of higher (but still small) levels of arsenic was hazardous to human health or not. Regardless, the EPA banned it's consumer use several years ago.
The new pressure-treated-kid-on-the-block is ACQ: Alkaline copper quat. There is no arsenic in this, just more copper, which does leach. I've been to several ACQ lumber-manufacturer websites and they all say in the "safety" information
Do not use pressure-treated wood in circumstances where the preservative may become a component of food, animal feed, or beehives.
I'm having a hard time finding the USDA's official ruling on whether pressure treated lumber can be used in organic farms (maybe for hog pens, for example). I have found that Ohio Ecological Food & Farm Association, a National Organic Program (NOP) certifier,
does not allow pressure treated wood on new construction on organic farms. Because NOP certifiers are the ones that inspect USDA organic farms, I'm suspecting it isn't allowed.
Personally, I don't see the point in building a new raised bed with pressure treated lumber. I can see the argument of just using a barrier if you inherited a pressure treated bed on your property. However, the basic premise of organic gardening is to nourish your soil. Having copper (a fungicide & insecticide) needlessly leach into your soil, in my opinion, isn't nourishing...it's potentially killing beneficials. I don't really care if it's just on point of contact or not. Leaching is leaching and it's the principle of the thing.
I'm not some elitist, though, that says you need to spend thousands on building raised beds instead of a few hundred. Untreated pine is CHEAP and lasts about as long as the average homeowner plans to stay in their house. Freecycle and Craigslist abound with cheap and free options for raised beds like cinder blocks, broken pieces of cement and scraps of cedar/redwood. Then there's also the option of using hay bales.
So, why do I bother gardening with my pricey composite lumber boards? Because *not* gardening isn't an option. Over the past few years, my garden has given me so many precious moments and delicious meals. I remember when my first seeds sprouted-- it gave me the inkling of how a proud mama feels. I remember our precious few strawberries which were the tastiest I've ever had (the chipmunks agreed). Chocolate-dipped ground cherries remind me of being hugely pregnant, with empty cupboards, and needing something chocolate-y *right now*.
I also garden to know where my food comes from...and to teach my child that baby carrots have tampered ends like "big" carrots and are not shaped like chubby thumbs. Nothing tastes better than a home-grown tomato too!
And, finally, I garden to create a better environment around my house and my neighborhood. I suppose this includes my ornamental garden as well. Walking around my block it becomes clear that my neighbors don't have nearly as much wildlife in their yards. I see gold finches (and crazy looking birds I don't know their name!) in addition to the robins and crows and sparrows, a praying mantis climbed up my leg last summer and ladybugs are far more common now than when we first moved in.
These things make gardening worth more than the cost of my raised beds for me. Your mileage may vary.
The garden is looking awesome right now. The cukes and pole beans are filling up their trellises, the lettuce hasn't bolted yet and the tomatoes seem to be growing a foot a week. Oh, and the zucchinis! The zucchinis! I think at least 1 plant is going to need to go. I planted a bunch b/c I didn't label & I was concerned one could have been a winter squash. I'm just one person...that can't eat the output of 5 zucchini plants.
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