Can you use pressure treated wood for raised garden beds

Raised garden beds are popular, practical, and relatively easy to build. Their simple construction can be customized to fit into any landscape, and they are an ideal way to grow vegetables, flowers, or herbs. A cost-saving alternative to Cedar, treated-wood products work very well when constructing raised bed gardens.

Raised beds offer many benefits and advantages for gardeners:

• Improved drainage
• Easier to improve soil quality
• Easier weed control
• Easier to water
• Fewer pests and rodents
• Less physical strain for the gardener
• Improved accessibility for elderly, disabled, or individuals with physical limitations

TIP #1:
If there’s a concern about vegetation coming in contact with treated wood, a liner can be used but is not required.

TIP #2:
Orient embedded support columns so only treated ends are in ground contact.

INSTRUCTIONS FOR BUILDING A RAISED GARDEN BED

Materials List for Raised Garden Bed:

• (6) 2″ x 8″ x 8′ Pressure-treated boards
• (1) 4″ x 4″ x 8′ Pressure-treated post
• (1) Box of 3″ — #8 Galvanized all-purpose screws

Building Steps:

• Use 4 single 8′ 2x8s for the long sides of the bed. Drill pilot holes in both ends of the two side pieces when they will connect to the ends of the other two side pieces.
• Cut four lengths of 2×8 at 48″ for the sides. (You should be able to do with a single 8′ board.) Drill pilot holes in both ends of these pieces as well.
• Connect the sides with 3″ deck screws.
• Attach a piece of landscape fabric to the bottom edges using galvanized staples. Leave some slack in the fabric, allowing that the weight of the soil with stretch the fabric.
• Add soil and start planting!

Download Instructions for Your Raised Garden Bed Here —Raised Bed Instructions

Q:

I am considering using some 2x6 inch material for a small raised bed for strawberries. My first thought was to consider pressure treated lumber, but I have read conflicting articles on the the safety of this product, with the chemicals possibly reaching the plants. Others claim this doesn't happen and the lumber is safe. I would appreciate your opinion on this matter.

A:

The safety of pressure treated lumber for raised bed gardens has been examined by several researchers.

From what I've seen, the consensus is that the chemicals do leach out of the wood into the soil and are uptaken by the plants in very small amounts. However, I haven't seen any research that suggests the level of the chemicals is significant enough to be of concern for human health.

Of course, the primary concern with using pressure treated wood in raised-bed gardens has been with the arsenic in CCA- (chromated copper arsenate) treated wood. This publication from Pennsylvania State University does a good job describing the risks of using both CCA-treated wood as well as ACQ-treated wood: Environmental Soil Issues: Garden Use of Treated Lumber. With regards to CCA, they state, "Although the plant and human health risks from garden uses of CCA-treated lumber appear to be extremely small, there are steps gardeners can take to further reduce any such risks."

One of the steps they recommend is to use wood treated with ACQ - "This is an alternative wood-treatment chemical that contains no arsenic, chromium, or any other chemical considered toxic by the EPA."

If you are shopping for treated lumber nowadays, I don't think you'll find CCA-treated material in the home centers anyway since its use was restricted by the EPA in 2004. It will be more likely be ACQ or some other chemical.

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Sam Angima | Aug 2008 | OSU Extension Catalog Peer reviewed (Orange level)

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