Wood Preservatives: Treated Lumber (5027)

The recent banning of wood preservatives is causing many gardeners to be concerned about using treated lumber in gardens and landscapes. Many of the old standard products such as creosote and pentachlorophenol are no longer used to preserve lumber due to health and environmental risks.  So what is safe for your landscape and garden?

Use untreated lumber that is naturally long-lasting, and replace it as needed.  Long-lasting lumber such as oak, cedar, and redwood may be more expensive, harder to find and may evoke other environmental concerns.

Some other alternatives include stone, cinder block, brick and other building material.  Select long-lasting materials that don't change the soil's pH, but do complement your landscape design.  Remember, you can mask building materials with vines, ground covers, and creeping perennials and shrubs.

If you do use treated lumber, use lumber that minimizes the potential harm to plants and the environment.  Pressure-treated lumber is the easiest to find.  This green-tinted lumber has been treated with either chromated copper arsenate or ammoniated copper arsenate.

Research indicates that these materials bind tightly to the wood and have a low tendency to leach into the soil.  But remember, research on the uptake of these arsenate preservatives into fruits and vegetables or their appearance in the groundwater is limited.

You can no longer buy creosote-treated lumber because of human health concerns: Creosote also harms plants.  It also leaches into the soil for several years and gives off vapors, in diminishing amounts, for seven to nine years. Limited research is available on the risks to plants and the environment from creosote. The safest alternative is not to use creosote-treated lumber in the garden or landscape.

Pentachlorophenol, also called "penta-treated lumber,” is also off the market.  Penta contains dioxin, which is a carcinogen. Like creosote, it gives off toxic fumes that harm people, plants, and animals.

Over-the-counter preservatives are also available. You can paint copper and zinc napthanate on lumber. Lumber treated with these products won't last as long, but researchers consider it less toxic than previously mentioned products.

If you use treated lumber, reduce the human, plant, and environmental risk of wood preservatives by painting or sealing them into the lumber. This prevents the preservative from leaching into the soil and possibly the groundwater.

Always wear rubber gloves and a dust mask when sawing and handling treated lumber, and avoid extended contact with bare skin. Read and follow all label instructions on the product you use.

Finally, always consider the cost and potential risk to you, your plants and the environment before you buy landscape and garden materials.

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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