Railroad Tie - Raised beds- For my information purposes only
Construction materials
The choice of framework to use for walls depends on the availability and expense of the construction material, as well as the desired appearance of the final product in the landscape. Treated landscape timbers and used railroad ties are popular materials. Naturally rot-resistant lumber, such as redwood or cedar, may also be used. Other possibilities include concrete blocks, bricks and stones, or synthetic lumber made of recycled plastic. A group of half barrels can make a convenient raised bed for use on a patio (Figure 2). For a consistent look, match materials to those used elsewhere in the landscape.
Generally, wood-based products are less expensive than stone or masonry materials. However, resourceful gardeners may be able to find used bricks, concrete blocks or other materials at little or no cost.
Certain national gardening publications have raised concerns about the safety of using treated lumber in food gardens. Pressure-treated lumber uses CCA (chromated copper arsenate) or ACA (ammoniacal copper arsenate) as a preservative. However, studies done by Texas A&M Agricultural Extension Service showed insignificant movement of these compounds into surrounding soil. Pressure-treated lumber has no proven effect on plant growth or food safety. However, on Feb.12, 2002, the U.S. Environmental Protection Agency (EPA) announced a voluntary decision by the lumber industry to move consumer use of treated lumber products away from a variety of pressure-treated wood that contains arsenic by Dec. 31, 2003, in favor of new, alternative wood preservatives. Alkaline cooper quaternary (ACQ) is a relatively new wood treatment that is available in some areas of the country. This product is higher in copper than CCA but is free of arsenic.
Creosote, which is used to treat railroad ties, may cause injury or death to plants that come into direct contact with it. After a few years the effect diminishes. Old, discarded ties do not injure plants (Figure 3). However, injury may occur if ties are still oozing black, sticky creosote or smell intensely. If you are uncertain about the safety of treated lumber, place a heavy plastic liner between the treated lumber and soil used for growing plants to prevent direct contact of plant roots with the treated lumber. Be careful not to tear the plastic when tilling the bed.
Figure 3
Old railroad ties make a satisfactory raised bed if they are not oozing creosote, which could injure plants.
Pasted from <http://extension.missouri.edu/publications/DisplayPub.aspx?P=g6985>
