Q.   Can treated timber be used in gardening projects?

A.   Treated timber is ideally suited to the long life expected of landscaped gardens, grape or tomato stakes, vineyard supports, retaining walls, trellises, garden furniture, compost bins, walkway steps, flower bed edging, planters, etc. Any assertion that gardeners should not grow edibles in planters or raised beds made with treated timber is without basis. Studies have shown that preservatives such as CCA and creosote are not absorbed into food crops like grapes, tomatoes and cucumbers. Some root crops like carrots and beets have been reported to pick up small amounts of arsenic from CCA, but it is in an organic non-toxic form and in any case is largely removed by peeling the vegetable. In tests of creosote-treated wood, no creosote was detected at a threshold of 660 parts per billion.

Pentavalent arsenate, the kind used in wood preservatives, should not be confused with commercially produced trivalent arsenic, which is not used in any wood preservative. Pentavalent arsenate occurs naturally in the soil, water, air, plants, and in most living creatures, including humans.

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