Raised beds are a fantastic way to increase usable gardening space outdoors even when the ground itself isn’t all that forgiving. With the increasing awareness of urban gardening coupled with a tremendous interest in DIY projects, some are taking it upon themselves to build their own raised beds instead of buying a ready-made and while that can be a great time and money saver, there are some things that you should be aware of should you choose to build one yourself.
When using plywood and other pressure treated woods in the construction of raised beds, you should know that treated wood products contain varying levels of arsenic, chromium and copper. Knowing that these elements are at play may be enough to scare you away, but the human body actually requires small amounts of all three of these elements and the levels at which they are released into the soil cannot be broadly stated or even estimated as there are a variety of factors that can impact it. Factors such as the amount of surface area that is in contact with the soil, as well as the acidity of the soil can work together to determine just how much of the elements are released into the soil and how readily they are absorbed.
If you have beds that are made of treated wood, you can reduce the risk by lining the inside of the beds with a heavy gauge plastic. When planting edibles in questionable raised beds, the risk can be further reduced by planting all crops no closer than 12” away from the wood surface. If you have reason to believe that your raised beds may have been constructed from treated wood and want to be certain of the quality of the soil, you can test your soil easily. Maintaining a soil pH as close to neutral as possible. This will help reduce the availability of arsenic, chromium and copper to the plants in the bed.