Using pressure-treated wood for urban planter boxes where you grow food requires careful consideration. Historically, wood treated with chromated copper arsenate (CCA) contained arsenic and was deemed unsafe for edible gardens. However, since 2003, most residential pressure-treated lumber uses safer preservatives like Alkaline Copper Quaternary (ACQ) or Copper Azole, which are considered low-risk for garden use.
For maximum safety, experts recommend lining the interior of the planter box with heavy-duty polyethylene plastic. This barrier prevents soil contact with the wood, minimizing any potential chemical leaching. Ensure the liner has drainage holes.
Alternatively, opt for naturally rot-resistant woods like cedar or redwood, though they are more expensive. Concrete blocks, composite lumber, or untreated pine with a shorter lifespan are other viable options.
Ultimately, modern ACQ-treated wood with a proper liner is generally accepted by many gardeners for growing food. The key is preventing direct soil-to-wood contact and understanding the specific treatment used on your lumber.