We apartment dwellers have turned a once grassy area into garden plots. There is a compost pile with redworms, some raised beds, and the decrepid skeleton of a greenhouse. I have recently built three more raised beds, one of which I gifted to a friend who has been using the garden space for many years.
The old 4" thick salvage boards I used to build the new raised beds are from the old bridge here at the apartments; they were pressure treated when manufactured, probably in the 1970’s or 80’s. It has been suggested to me to use a plastic liner to keep the soil separate from the old boards — just in case they might be leaching toxic chemicals even after all this time! On the other hand, I was told by the maintainance guy that it has been at least 30 years since the boards were manufactured, and especially with our wet climate the chemicals have all been substantially leached out, thus the reasoning for replacing the bridge. Although using one raised bed without plastic does present an opportunity to do a scientific study on whether or not arsenic is still leaching out and if so to what degree it is being uptaken by certain plant species. Even so, if it was found to be leaching, then it would also be contaminating the soil we want to use to grow food in. Since I have no place to do an isolated experiment, I will not pursue this experiment. I would like to take the paranoid route, and if people want to share the cost, I will coat the boards with an opaque acrylic or polyurethane oil base and/or wrap all the boards in plastic to prevent possible leaching. Otherwise, my financial situation and the fact that some of the boards are in pretty rough shape (rough surfaces, cracks, and rot pitting) has me leaning towards the opinion that the chemicals have mostly if not totally leached out over the years.
Here are studies that may be of use to anyone considering using treated wood in gardening:
- Arsenic Availability from Chromated Copper Arsenate (CCA) Treated Wood
- Arsenic Uptake Released from CCA Treated Lumber by Florida Vegetable Crops
- Coatings Minimize Leaching From Treated Wood
- Copper, Chromium And Arsenic In Soil And Plants Near Coated And Uncoated CCA Wood
Unfortunately, this garden has had a persistent thief problem… every year some of our plants are taken. I went out one day to harvest broccoli and cauliflower, and a lady was harvesting them; I asked what she was doing and she said that she paid a guy $10 for all she could eat… liars and thieves! Sheesh. About half of the salvage boards that were to be used to make raised beds were stolen… so I was only able to build three. Years earlier, the plastic on the greenhouse was taken down by thieves in the night, and the gardener (he still gardens here) who put it up never replaced it because he anticipates it being stolen again. It is sad that there are a few people who look at a garden as an opportunity to steal, and this might be why more people haven’t even bothered to garden here. I will continue to as long as I live here… keeping my chin up… some people don’t believe in karma… some people do.
September 2012: I have recently moved to a location too far from the apartments to conveniently upkeep the garden… but there are other residents who are continuing the tradition and have expanded the garden by building more raised beds.