Do you recommend Copper treated wood for raised bed gardens?

Asked May 11, 2013, 9:44 AM EDT

I am interested in building a raised bed garden using Copper treated wood so that the structure does not deterate. I have heard that the pressurized lumber (micronized copper azole) may leach into the soil. Could using 6mm plastic wrapped around the 6in x6inx12ft long boards help in stopping this to occur, or should I look for other wood to build a raised bed?

Colorado fruits and vegetables raised bed gardening horticulture

1 Response

I am sorry but I am unable to find a researched based answer for your question. Research conducted at the University of Minnesota using chromated copper arsenate (CCA) pressure treated lumber showed some plant uptake of arsenic but the amounts accumulated were well within U.S. Public Health Service standards. You can line garden beds made of CCA-treated wood with plastic sheeting on the base and sides of the bed to separate the wood from the soil. For more information, see: Vegetables, and especially root crops, should be planted at least 12 inches from CCA treated lumber. Thoroughly wash all vegetables grown near treated lumber. Plant tissue concentrations of these metals are highest in roots, especially near the root's surface. If you have a wooden structure in your landscape built between 1970 and 2004 it is likely that CCA treated lumber was used. To find out if you have CCA treated wood in your landscape there are kits that can be purchased from several sources (e.g. Pieces of lumber that bear codes like CBA-A or CA-B which indicate they were treated with a Copper Azole-based material. Copper is the primary decay-preventing chemical in all of these treatments. I am unable to find a paper that lined CBA-A or CA-B wood beds with plastic. Micronized copper quat (MCQ) is the only wood preservative certified not to release copper. One drawback to using lumber containing copper is rapid corrosion of fasteners (screws, nails and bolts) and connectors (corner braces). For this reason it is essential to use hot dipped galvanized fasteners and stainless steel or copper corner braces for raised beds. I could not find any papers that lined MCQ products with plastic.‎ Naturally rot-resistant lumber, such as redwood or cedar, may be used