Is It Ok To Use Treated Lumber For Raised Garden Beds?

Raised garden beds are a great way to extend the growing season, improve drainage, and protect plants from pests and diseases. However, one of the most important decisions you’ll need to make when building a raised garden bed is what type of lumber to use.

Treated lumber is often used for raised garden beds because it is resistant to rot and decay. However, there is some concern that the chemicals used to treat the lumber could leach into the soil and harm plants.

What Chemicals Are Used to Treat Lumber?

The most common chemicals used to treat lumber are chromated copper arsenate (CCA), pentachlorophenol, and creosote. These chemicals are effective at preventing rot and decay, but they can also be harmful to humans and the environment.

• CCA is a water-borne preservative that contains arsenic, chromium, and copper. CCA is no longer used to treat lumber for residential use, but it may still be found in older structures.
• Pentachlorophenol is an oil-borne preservative that is used to treat lumber for industrial and commercial use. Pentachlorophenol is a known carcinogen and can cause skin irritation, respiratory problems, and reproductive problems.
• Creosote is a coal tar derivative that is used to treat lumber for railroad ties, utility poles, and other outdoor structures. Creosote is a known carcinogen and can cause skin irritation, respiratory problems, and digestive problems.

Concerns About Treated Lumber in Raised Garden Beds

The main concern about using treated lumber in raised garden beds is that the chemicals used to treat the lumber could leach into the soil and harm plants. Studies have shown that CCA and pentachlorophenol can leach into the soil and contaminate plants. Creosote is not as likely to leach into the soil, but it can still be harmful to plants if it is ingested or absorbed through the skin.

In addition to the potential for leaching, treated lumber can also be harmful to soil organisms. Soil organisms are essential for breaking down organic matter and cycling nutrients. The chemicals used to treat lumber can kill soil organisms and disrupt the soil ecosystem.

Alternatives to Treated Lumber for Raised Garden Beds

If you are concerned about the potential risks of using treated lumber in raised garden beds, there are a number of alternatives available.

• Cedar is a naturally rot-resistant wood that is safe for use in raised garden beds. Cedar is more expensive than treated lumber, but it will last longer and is less likely to leach chemicals into the soil.
• Redwood is another naturally rot-resistant wood that is safe for use in raised garden beds. Redwood is also more expensive than treated lumber, but it is very durable and will last for many years.
• Douglas fir is a less expensive option than cedar or redwood, but it is not as rot-resistant. Douglas fir can be treated with a non-toxic preservative to extend its life.
• Pine is a common choice for raised garden beds because it is inexpensive and easy to work with. However, pine is not very rot-resistant and will need to be replaced more often than other types of wood.

Conclusion

The decision of whether or not to use treated lumber for raised garden beds is a personal one. There are both risks and benefits to consider. If you are concerned about the potential risks, there are a number of safe alternatives available.

Questions and Answers

1. What are the most common chemicals used to treat lumber?

   • CCA, pentachlorophenol, and creosote

2. What are the concerns about using treated lumber in raised garden beds?

   • Chemicals can leach into the soil and harm plants, kill soil organisms, and disrupt the soil ecosystem.

3. What are some alternatives to treated lumber for raised garden beds?

   • Cedar, redwood, Douglas fir, pine

4. Is it safe to use old treated lumber for raised garden beds?

   • No, old treated lumber may still contain CCA, which is a known carcinogen.

5. How can I extend the life of untreated lumber in raised garden beds?

   • Apply a non-toxic preservative to the lumber before use.