I sent this link http://www.motherearthnews.com/do-it-yourself/build-a-cold-frame-ze0z11zkon.aspx to my dad last year, thinking he could help me build this for my garden this winter. I promised to bring materials and beer :-) in return for using his tools, space and knowledge to put this together since it’s not a project I’d ever attempted before. Imagine my surprise when he called me last night to tell me he had it almost done and ask if I wanted to pay more for plexi or less for glass.
After I recovered a bit, we started talking about the materials he purchased on my behalf and I learned that he bought pressure-treated plywood for this project thinking it was a better choice. I was concerned as I try to be organic and understood that pressure-treated wood was a no-no in the garden. My beloved father called me today to tell me that he called Mother Earth News and they told him that there should be no issues with using the cold frame in my garden.
I feel terrible about this because my dad was so nice to work on this for me but I’m concerned about any chemicals that might be introduced to my garden. I trust my fellow Folians and am wondering if anyone has some input about this.
You should have ACQ, short for Alkaline Copper Quaternary, treated lumber. The original CCA (Chromated Copper Arsenate) treated lumber was discontinued. The concerns originated with CCA treated lumber. For a clear explanation, see the below link. The new compounds are most hazardous to your metal fasteners by promoting accelerated corrosion via electrolysis. Check to be sure it isn’t old stock of CCA, but wouldn’t think that possible in NY.
EDIT: I should add that if after review of the above information you are still concerned. Prime and paint all surfaces with a good exterior latex paint. This will prevent any leaching.
Arsenic based Pressure Treated Lumber is no longer able to be sold in stores now for several years. There was a 180 day grace period to sell off old inventory but that was a long time ago. If he bought the lumber in the last two years, then you’re ok. There are still people that won’t use it, but it is safe as far as anything harmful bleeding into your produce. If you are concerned them line the inside of the frame with plastic. I did that on my strawberry raised beds covering the wood on top, side, and bottom edge of each plank with heavy plastic with staples. I’m not concerned but a little overkill doesn’t hurt. Also, hopefully he used coated deck screws because regular screws will rust away real quick in pressure treated.