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Vegetable Garden

By on March 26, 2014
use redwood or oak for raised gardens

Question

I am planning on using pressure treated landscape timbers for a raised vegetable garden. Others have told me, that I need to be concerned about the chemicals that may leach out and affect the vegetables that I plan to eat. Should I be concerned? What chemicals may leach out? Do you know if these chemicals are likely to be transferred into the food I plan to eat? Thanks for your assistance.

JLB

Answer

JBL, Yes, it is our opinion that there would be a danger using pressure treated wood to surround a garden. Pressure treated lumber is injected with chemicals that resist damage by moisture and pests. In the past, the most common chemical used was copper chrome arsenate, which many consider unsafe. Visit the EPA’s copper chrome arsenate page for more information. Some similar but safer chemicals used now are copper azole and amoniacal copper quat. There are several degrees of concentration of the chemical depending on the intended use of the wood. For example: fence posts that will be underground contain a higher concentration of the poison than fence boards that will not be used underground. However, the degree of concentration is academic when it comes to any possibility of ingesting the chemical. The companies that make pressure treated wood will tell you that it is safe for deck surfaces and furniture. We disagree. Anywhere that a “chewing/chomping” toddler can easily access pressure treated wood, we feel, is cause for concern. We think that pressure treated lumber is superior to any other kind for use outside (deck framing ? not the finished decking) or in contact with the earth or other regularly wet surfaces (retaining walls, foundation mudsill, etc.). If it were our garden we would use plain wood. Cedar and redwood are good choices. And, good luck!

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