As avid gardeners, we often wonder if pressure-treated wood is safe for use in our veggie garden boxes. While it is not considered organic, pressure-treated wood can be safe for both humans and the microbiology in the soil. It is important to note that safety is perceived differently by different individuals.
In this video, we will explore the safety of pressure-treated wood, the impact on soil microbiology, and the use of buffers to prevent leaching. We will also discuss identifying treated lumber for garden use and alternatives to treated wood. Our goal is to provide you with the information you need to make an informed decision about using pressure-treated wood in your garden.
As regenerative gardeners, we understand the importance of ensuring that our gardening practices do not harm the soil's microbial or plant life. While pressure-treated wood is not organic, it can be safe for use in veggie garden boxes.
The lumber industry and the EPA banned the use of arsenic in chromated copper arsenic treatment of wood in the U.S. on January 1st, 2004. Since then, the industry has switched to much safer copper compounds called ACQ CA and MCA. These compounds still cannot be used for certified organic growers, but they are safe for home gardeners who care about the health of the microbes in their soil.
According to the Iowa State University extension program, copper residue found in soils of raised beds from treated lumber is 10 to 100 times lower than what is considered toxic to humans. However, as regenerative gardeners, we want to ensure that it is safe for the microbial life in the soil. Copper, the active ingredient of these compounds, is antimicrobial, and the coronary ammonia also acts as a biocide, which helps preserve the wood.
To further ensure the safety of our soil, we can use buffers between the treated wood and the soil. The American Wood Protection Association suggests placing a plastic sheet between the treated wood and the soil. Another option is to use old, rotting wood as a buffer, a technique called Hugo culture. This rotting wood has already become a host for beneficial fungi and other microbes, and it acts like a sponge to store water and release it in drier times. The wood will slowly release nutrients into the soil as it rots.
Most leaching from treated lumber occurs in the first few months of use, according to the National Pesticide Information Center. By the time the old wood is fully decomposed, any leaching that may occur will be inconsequential.
When selecting pressure-treated wood, it is essential to look for the right tags. Not all treated lumber is the same, and there are different variations of treatments depending on the application. The American Wood Protection Association recommends category 4A or higher for garden boxes. Alternatively, untreated cedar is an ideal option, but it can be costly.
In summary, using pressure-treated wood in garden boxes is safe for humans and the microbiology in the soil, although it cannot be used for certified organic growers. To ensure that preservatives do not leach out into the soil, we can use plastic or old rotting wood as a buffer. When purchasing treated lumber, we should look for the right tags to ensure that we are using the appropriate type. By taking these steps, we can maintain healthy soil and grow healthy plants.