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Treated Lumber in Raised BedsNote: CCA treated lumber was taken off the market. For more current information on treated lumber, please see Treated Lumber in the Garden.Gardening in raised beds can be just the answer for would-be gardeners who would love to grow their own vegetables and flowers but lack the space or physical ability for a traditional garden. However, recent controversy regarding chemical wood-preservation treatments has left many gardeners wondering about the safety of treated lumber. Certainly, any discussion of potential toxicity must be prefaced with the knowledge that there can be great variability in sensitivity to pesticides in the environment. Some folks can react to very low levels of a chemical that most other people don't react to at all. Also, keep in mind that toxicity is relative to dose and exposure. But for the bulk of the population, pressure-treated lumber appears to be a reasonably safe choice for gardening structures. Pressure-treated lumber is saturated with a fungicide made from salts of chromium, copper and arsenic (CCA). All three chemicals occur naturally in soil, because they are part of the parent rock material. While some of the chemical components are potentially toxic to humans, the fungicide is applied to the wood under high pressure so that there is little movement of the fungicide out of the wood. However, some leaching is possible. Fortunately, the chemicals become bound to soil particles except in very acid soils (pH 4.0 or lower). So, even when leaching does occur, the chemicals are not likely to be taken up by plants. Treated lumber is not without some risk. The Environmental Protection Agency and the manufacturers of treated lumber advise that: 1. Treated wood should only be used for outdoor structures. 2. A dust mask should be used when cutting treated wood. 3. Scraps of treated wood should not be burned. 4. Sawdust and/or chips of treated wood should not be used in compost or as mulch. While the risks from treated lumber are low if used properly, there are plenty of other materials available for building containers and raised beds. Natural, rot-resistant woods, such as redwood or cedar, make excellent raised beds, but these materials are generally quite expensive. Plastic lumber made from recycled plastic is available in most places where lumber is sold. |
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Writer: B. Rosie Lerner |
Editor: Oliva Maddox, (765) 496-3207 |
Last updated: March 27, 2006
Questions about this page should be sent to homehort@purdue.edu
The URL for this page is http://www.hort.purdue.edu/ext/treatedlumber.html