Raised vegetable beds can be temporary structures made of piled earth or more permanent beds bordered with frames made of stone, wood or synthetic timber. Some materials with an unknown history are effectively treated with oil-based stains.
Materials And Contaminents
Timber from unknown sources may have been pressure-treated with chemicals containing arsenic or copper. Sleepers contain or are coated with creosote, which damages plants. The United States Environmental Protection Agency does not recommend using sleepers in home landscapes.
Some woods, like redwood and cedar, require staining for aesthetic reasons. Other woods require staining to prevent rot and deterioration. Stain wood with an oil based stain in order to prevent the wood from deteriorating. According to Purdue University's Department of Horticulture, applying oil-based stains also seals toxins into the wood and prevents leaching into soil and edible plants.
Landscaping with reclaimed materials -- sleepers, tires and whiskey barrels -- is seen in urban gardens. Many gardeners with this style preference work around the possibility of contamination by lining the container with plastic. The entire surface does not need to be covered. Simply drape the plastic between the area where the container meets soil.