To Use or Not to Use, That is the Question - About Pressure Treated Wood

Karen, of Springdale, had planting boxes of pressure treated wood made for her last year. She planted flowers in the boxes and added a few carrot seeds for visual interest. She also had a vegetable garden in the backyard that didn’t contain any pressure treated wood in which she also planted carrot seeds. When she harvested her vegetables she discovered the carrots in the boxes made of pressure treated wood did much better than the carrots in the backyard garden. However, having heard the concern surrounding the safety of pressure treated wood she opted not to eat the carrots. As the new planting season approaches she wonders if all the fuss about the pressure treated wood is something to worry about or not.

For those of you that may not know what the fuss is let me give you a short run down. Pressure treated wood, known as CCA treated wood, is wood that has been treated with chemicals to give it a longer life span without rotting. Unfortunately the chemicals have been known to leach out of the wood. This brings into question the safety of using it. There has been much debate about the safety of using pressure treated wood, especially in playgrounds. Here I address the question of it’s safety for use in the garden.

After much research, the jury’s still out on this one. I found three possible answers to the question: 1) Don’t even think about it; 2) Go right ahead; and 3) Proceed with caution. I’ll tell you where each answer comes from and you can make up your own mind.

Don’t even think about it

Organic gardeners don’t like the idea of any chemicals coming near the garden and say if you already have pressure treated wood in your garden replace it with natural rot resistant wood such as cedar or redwood.

Go Right Ahead

The producers of the wood say that while there is some leaching of the chemicals there is not enough to cause concern. A study done by Paul Cooper, a wood scientist, of the University of New Brunswick showed that the most leaching happened in the first rainy season after the board was installed and the soil closest to the board showed a higher concentration than the soil further away. The overall amount of leaching, however, is said to be of no concern. Rufus Chaney at the USDA says that “high levels of inorganic arsenic in soil will kill a plant before there's enough arsenic in the plant itself for you to consider not eating it.”

Proceed with caution

Those that acknowledge potential danger suggest that painting a sealer on the wood or covering it with heavy plastic sheeting will provide more protection and thus take away any concern.


So there you have it. Now it’s up to you to decide. If you want to read up on the information and studies for yourself you can check out the links on the online home of the column at http://greenthumbsandgreenhorns.blogspot.com .

I found it interesting that there seems to be more concern about how to safely get rid of the pressure treated wood than there is about the safe use of it. One source I checked out says that "Because of this concern, the wood products industry and EPA have agreed to stop selling CCA-treated wood by the end of 2003." So the question we need to ask ourselves now is not to use or not to use, but to keep or not to keep.

If you have any comments on this or any other gardening related topics I’d love to hear from you. Call me at 673-4825 or email me at greenhorngardener@yahoo.ca .