Raised vegetable garden beds

Asked September 21, 2019, 12:03 PM EDT

I read that there are many bad choices for consumable vegetable garden bed framing materials due to the leaching of chemicals into the soil. So far, no one has given me a good option to use for materials that would be safe for consumable food. Do you have a suggestion for a safe material? Not a mound. Not creosote. Not treated lumber. Not concrete. Not cedar. Not redwood. Everyone has a list of "not to use". What SHOULD I use? What is considered safe?

Clatsop County Oregon

2 Responses

It definitely can be difficult to make a decision about what materials to use to frame a raised bed. From your description it sounds like you are growing edible crops (veggies) and are not interested in an unframed/mound type raised bed.

There is minimal research data available on exactly which materials are considered safe but some materials that have been discovered to be more risky choices. This can be frustrating when you want a clear answer. Unfortunately, there just haven't been studies done on long-term raised bed framing materials utilized under all the different growing conditions, soil, fertilizer regimes, & edible plant combinations. Basically proving something "safe" is considerably more difficult than proving that something is a potential risk.

As you have found from your own research, there is data available that has deemed certain materials more risky. This includes older treated lumber and railroad ties, for example, which have been found to leach small amounts of the wood preservative into the surrounding soil. So these materials are no longer recommended for use in edible gardens.

Using untreated wood as a framing material is likely the least risky choice available (compared to treated wood, plastics, etc.) that also offers cost effective and flexible building plans. Plan to rebuild or maintain beds sooner than beds constructed from treated wood or other materials. Using a naturally decay resistant wood (redwood, cedar) is more expensive up front but will last a little longer in our wet winters.

Hope this helps and thanks for using Ask An Expert,

Thank you very much for your answer. I appreciate your honesty and complete explanation. It does seem like the natural woods are the better choice. There are no guarantees. But I like to try to make informed decisions and I sincerely thank you for your response and the thought you put into it.