Treated lumber OK for beds
Q. Is treated lumber safe to use for sides of a raised bed vegetable garden?
Pat from Columbiana
A. Treated lumber is commonly used in raised beds in many gardens and community gardens – nearly every place where raised beds are needed or wanted.
Treated wood is generally used over untreated wood because it is in contact with the ground. Rots (fungi), insects and other natural forces work on the lumber to break it down just like a downed tree is decomposed on the forest floor. When wood is treated, it lasts significantly longer in outdoor settings.
If you are out searching on the internet, you will find an old Penn State University Extension fact sheet that gives many details about CCA, a chemical that is no longer used to preserve wood for use as of 2004. This fact sheet gives details about the 2004 end date for use of CCA products. Thus, this fact sheet is out of date and not applicable to current treated wood available for purchase by consumers.
According to the University of Maryland Extension, the new product used most often to treat wood is Alkaline Cooper Quaternary (ACQ). The EPA considers this to be a low-toxicity product. More information is available about ACQ through the link to the Maryland fact sheet below. In addition, this sheet gives other options for preserving natural wood to be used for a raised bed vegetable garden.
Although raised beds offer many advantages for those who cannot bend to garden at ground level, there are options when raised beds are not required which are beneficial and save money. Many community gardens instantly think of raised beds when designing their space. Personally, I would like to see more money spent on improving soils, such as adding compost or other amendments. Constructing raised beds should be limited to where they are necessary for mobility reasons.
To make a raised bed without sides, simply mound soil and or amendments up to 15inches high and 4 inches wide so you can reach the center from both sides. This allows for improved drainage and warmer soils in spring to get crops planted earlier.
Before planting in any soil, a soil test should be completed to know what improvements are necessary. If you are adding new soil and/or compost, do a soil test after the mix is tilled. Although it is new material, there is no guarantee that the new mix contains the correct pH and nutrient levels which are necessary for vegetable production. Before planting in urban soils where a house was torn down or business site used to exist, the soil should be tested for lead.
To read the details about materials for raised beds and information on the chemicals in treated lumber, go to go.osu.edu/treated.
Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office plant and pest clinic at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.