Treated Wood and Your Raised Bed Gardens
Questions have been asked about the use of pressure treated wood in raised bed vegetable gardens. Various universities have studied CCA-treated wood in agricultural applications and found no indication of problems. Most recently, the County Extension of Texas A&M reviewed this matter and concluded, "...that arsenic was not leaching from timbers used in raised bed gardens varying in age from 6 months to 9 years of age." Nevertheless, the Hickson Corporation initiated a test program in 1992 to evaluate this use in more detail.
Three raised bed structures were constructed from 2" x 12" Southern Pine: one was made with Wolmanized® pressure treated wood and one with Womanized® Extra weather resistant lumber. These structures were divided into individual bins, so that the bottom and all sides of a bin were of the same material, i.e., all untreated or all treated. The bins were filled with potting soil (Majestic Professional Growers Mix) and various vegetables then planted. An automatic sprinkler watered the vegetables twice weekly for 15 minute periods. After twelve weeks, portions of the vegetables were harvested and analyzed for CCA components. Several vegetables were also obtained at a local grocery store and analyzed as well.
Vegetable Analysis, Dry Basis, mg/KG (parts per million)
|Vegetable||Untreated Wood||Wolmanized Wood||Wolmanized Extra Wood||Store Purchase|
Testing of Wolmanized pressure-treated wood in raised bed garden applications has shown that there is no uptake of the metal constituents into the vegetables