Using Pressure Treated Wood

I was doing some research on wood types and came across a relatively new type of PT, MicroPro. It's gone through some tests and seems to be okay to use with veggie gardening(though I tend to take everything like this with a grain of salt: ie: I'm waiting another 5 years before I see about Lasic surgery and I never buy a brand new microsoft operating system.). If I still had young kids, I'd probably skip it, but since I'm moving into the 40+ bracket and my daughter is in college, I might take a good look at using this, with some plastic wrapped on the inside and under the wood.

Below is the jist of things:

MicroPro Treated Wood Used in Agricultural Applications

MicroPro (micronized copper quaternary) and (micronized copper azole) treated wood may be used to construct raised bed gardens. The MicroPro treated wood process is certified by Scientific Certification Systems, Inc. (SCS) as an Environmentally Preferable Product (EPP) based on SCS’ Life-Cycle Assessment.
Recommended preservative retentions for MicroPro treated wood products are:

• For MicroPro (micronized copper quaternary) treated wood, the minimum
preservative retention should be 0.34 pcf for ground contact applications.
• For MicroPro (micronized copper azole) treated wood, the minimum preservative
retention should be 0.15 pcf for ground contact applications.

Very small amounts of copper and either quaternary or azole will migrate out of MicroPro treated wood over time. If it is desirable to avoid migration of any amount of copper, quaternary or azole into the soil of a raised bed garden, we recommend that a suitable thin plastic material be used as a barrier between the MicroPro treated wood and the raised bed garden soil.

The use of a plastic barrier will also help keep the raised bed garden soil within the bed area. For proper drainage, the plastic material should not be used underneath the raised bed garden soil.

For additional information on MicroPro treated wood, visit www.osmosewood.com.
April 2009

This is the reply from an email query I sent(the above was an attachment):

Thank you for your email and for your interest in YellaWood brand products.

Yes, YellaWood® brand products are approved for use in applications such as raised vegetable gardens. We would recommend that you use boards that are treated for “Ground Contact” applications since they will be in contact with the soil. You can find this notation on the end tag on each piece of YellaWood® brand products. I've attached a document that should help explain this usage in greater detail for you as well as a project plan to help you get started.

So, have you decided to go with this product?

I built both of my beds entirely out of PT lumber and plywood. After being "scared off" by an "expert" at Lowes (who told me I'd be putting Arsenic in my food), I went to several sites (including Yellawood) and looked into it to the best of my ability. There seems to be no evidence from a credible source of any trace amounts of copper transferring into vegetables from soil which was in contact with pressure treated wood. Since I wear a copper bracelet (which also has unsubstantiated effects) I figured I could simply quit wearing it and get less copper in my system than I'm deliberately adding now. Then - in a bow to a family member who falls down and twitches when PT wood is mentioned - I lined both boxes with "plant mesh" (that black plastic fabric stuff). Who knows? Your mileage may vary.

I ended up going with cinder blocks for the permanent beds. They're easier to transport in my car than 8 foot pieces of wood. However, from what I understand, there is currently no pressure treated wood on the market(unless you get some from a really old house) that can kill you outright. The old arsenic stuff has been off the market for many years(I've read somewhere that it was around 1980, and other places as recent as 2003) and the ammonium/copper stuff(ACQ), which is most commonly used, won't cause you to ingest arsenic.

Arsenic is formed when you smelt copper, so I wouldn't recommend burning treated wood.

For the record, I really do hate the internet when I'm researching things. It's a boon and a bane for reliable information.

While attending an edible garden symposium given by the LSU AgCenter, someone asked the question about using PT lumber. The speaker(from the AgCenter) said she uses it all the time and that it's fine to use.

If I liked the look of PT lumber, or could find a safe paint that will hold up in the weather, I'd have probably gone with PT lumber in the end.

@Unmutual, you might want to check if this particular brand of pressure treated wood is approved material for use with growing "certified" organic veggies. If it's a rather new product, it may or may not be listed yet by any of the organic regulatory agencies (e.g. NOP).

That would be a good indicator for whether it's safe to use for SFG boxes!!