Garden Boxes

Asked July 8, 2013, 11:14 AM EDT

I have some raised garden boxes, but it appears they are made from treated lumber. I have a concern regarding the toxicity of the plants growing in them. We found a dead rabbit that appeared to have eaten a bean plant. The boxes look new (within the last year).

Berrien County Michigan fruits and vegetables

3 Responses

There should be no problem using your garden boxes if you line the inside of the boxes with a heavy plastic or landscape fabric. If these boxes have holes in the bottom for drainage, you can poke a hole in the plastic to allow for the drainage. If these are raised beds, you only need to cover the treated wood with the plastic. If you already have these boxes planted and these are the plants you are concerned about, I would hesitate eating them. There are different kinds of preservatives used in pressure treated wood including creosote, arsenic (CCA), copper and other fungicides. If an existing bed was built with pressure treated wood, you should try to identify what kind of preservative was used. Most researchers agree that vegetable gardens should not be planted in beds made of coal-tar creosote treated wood, especially newly treated wood. Arsenic (CCA) treated wood is no longer sold at lumber supply stores; it was phased out a few years ago. Currently, treated wood available in lumber supply stores is treated with copper compounds and/or fungicides. Some studies have suggested that this treatment is safe for use in vegetable gardens. Alternatively, there are still concerns that the copper can leach into soil and accumulate. Research is on-going. I continue to recommend lining beds with a barrier to keep the soil away from copper treated wood. The dead rabbit could possibly be caused by the treated lumber. Without being tested, it is hard to tell. For further information, and to report incidents to the EPA, please contact the National Pesticide Information Center at 1-800-858-7378, or e-mail npic@ace.orst.edu.

Hope this was helpful. Please feel free to contact us again if you have further questions.

Thank you for your quick response. You mention I should have it tested. What were you saying was needing testing the soil, the rabbit, or the wood?

It would be interesting to have them all tested, including the plants, since you think the rabbit may have died after eating the bean plant. If you could perhaps first find out what the wood was treated with, you may not have to test the rest if it was a non-toxic material, such as a copper compound as mentioned in my earlier email. They claim that this is a safe preservative. I would double check that, though, because I think the jury is still out. I don’t know if you can find out what killed the rabbit. It could have been something entirely different and not related at all to the bean plant. There are some professional labs that you may be able to have these things tested at, but I’m sure there will be a cost. You can find a number of them by typing “test laboratories-Michigan” into Google. Toxicity from treated lumber can leach into the soil, so if this was a toxic treated wood then the soil is contaminated. There may be a way to cleanse the soil, but that would have to be researched further. It may be easier to remove the soil, cover the wood with landscape material or plastic, and refill the boxes. You did not mention how large these boxes are, so whether that would be feasible or not will depend on that. I don’t know what else to tell you, but if you have more questions, please ask me, and I will see what I can find out! Good luck!