Raised Garden Beds from Treated Lumber or Used Crossties?
By Digger & Gina McLean
Since the pandemic started, the good news is that more people are gardening. And with the current high prices of food, people are continuing to grow vegetables in their own back yards. A favorite of gardening enthusiasts is the raised bed. It's contained and compact and easily manageable for most any gardener. This wonderful trend has led to more and more questions about making garden beds out of treated lumber. Is it safe? Will it poison my plants or vegetables? A recent article in Building Products Digest says,"Of interest to the home gardener is whether any of the preservative components in treated wood used to construct a raised bed garden could render the food crop unsafe for consumption. The available evidence says no." The newer treating chemicals for residential lumber purchased at big box stores are primarily made of copper, which is widely used as a fungicide for plants and a disinfectant in swimming pool chemicals. An ongoing study at Oregon State University has found no difference in copper content in veggies grown in untreated wood boxed or treated wood boxes. Humans and plants need copper in small amounts as an essential element for life.
Another question is whether creosote crossties can be used to make raised garden beds. The answer is also yes. There is a lot of fear being raised about using old crossties for raised beds, but I'm not sure that fear is research based. Many people have used old crossties in their gardens for a lot of years with good results and by the time crossties are retired from service by the railroad, most of the creosote has already leached out of the wood. If you are still concerned about creosote leaching into your raised bed soil, you can cover the inside of the ties with plastic and then fill your bed.
Treated wood is a good choice for raised bed gardens and lasts longer than untreated wood. New and ongoing research suggests that wood treating chemicals are not leaching into garden soil and vegetables grown in bed using treated wood are safe for human consumption.