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Treated Wood Yields Safe, Durable Option
MISSISSIPPI STATE -- Treated wood products used for making picnic tables, decks or lining gardens are safe and durable options for sprucing up Mississippi yards.
Dr. Terry Amburgey, a Mississippi State University professor in the Forest and Wildlife Research Center, said oil-borne preservatives and water-borne solutions both offer excellent durability. However, wood freshly treated with oil-borne preservatives, such a pentachlorophenol or creosote, should not be used on decks or lawn furniture.
"Treated wood used around a garden will often outlive the person creating the bed and is absolutely safe," Amburgey said. "Old creosote-treated crossties used as flower bed borders do not pose a health hazard. If plants will grow around the wood, it's safe."
Research on wood preservatives is ongoing at MSU as companies develop new formulations. For instance, Southern Forest Products Association sponsored research on the durability of decking.
Amburgey said oil-borne preservatives like pentachlorophenol and creosote can function like a herbicide and kill or damage plants. Those preservatives most commonly are used on products such as railroad crossties and telephone poles.
"Generally, by the time that crossties make it into a garden setting, most of the solvent has dissipated. Old crossties often are used as garden or flower bed borders without damaging plants or harming people," Amburgey said. "Woods treated with both water-borne and oil-borne preservatives commonly last 20 to 30 years and sometimes as long as 50 years."
The most common water-borne wood preservative in the United States is chromated copper arsenate, or CCA, which is usually used on wood in smaller dimensions, such as outdoor furniture and decks. Amburgey recommended washing new CCA-treated products with a detergent and treating with a water repellent and reapplying the repellent each year. Washing will remove any possible surface deposits of preservative, and water repellents will retard the development of splits in treated wood. CCA is not harmful for garden use.
"Once treated with CCA and dried, very little of the chemical will leach out of the wood," Amburgey said.
