When you’re ready to construct a raised garden bed, cedar is a great selection for prolonging the life of the bed without needing to take care of it with chemicals. Whether you pick 1- or 2-inch thick wood is dependent upon a few things. No matter which you use, remember that 1-inch thick lumber is actually only 3/4-inch thick, while 2-inch lumber is 1 1/2 inches thick. And several of the cedars we use for building outdoor structures aren’t true cedars (Cedrus spp), however, also are part of the cypress family (Cupressaceae).
When building the sides of the raised bed garden, strength is important. Raised beds are typically 6 inches tall to get blooms and most vegetables, however, the beds to get root vegetables are up to 12 inches tall. Taller beds require more soil and result in more pressure exerted on the sides. When screwed together at the corners, thicker 2-inch wood is stronger than 1-inch, which makes it a better choice for bigger beds. But if you want to keep prices down, you can increase the strength of 1-inch cedar by attaching it into 4-by-4-inch corner articles using 3-inch deck screws.
Whether you pick 1- or 2-inch cedar boards to build your raised beds, then you want them to last as long as you possibly can. Thicker wood lasts years longer than thinner, and boards made of heartwood last longer than ones made from sapwood. Heartwood comes from the center of the tree and contains additional rot-resistant oils. Sapwood is located just under the bark. It’s softer and decays considerably more quickly than heartwood.
Cedar is precious for its ability to resist rot and insects strikes, however, its price keeps some people from using it. You can make it even more affordable by lining the interior of the boards using 6-mil black plastic. This keeps moisture off of the boards, when watering, prolonging the life of the raised bed. Don’t run the plastic across the breadth of the bed or you will create drainage issues. But because of the possibility of toxins leaching from the plastic, some gardeners do not consider growing in plastic-lined beds consistent with organic practice.
Eastern redcedar (Juniperus virginiana) is the most durable of all the cedars. It’s knotty and when left untreated, the heartwood can last 30 years or longer, even when in contact with soil. It resists insect strikes nicely and is the most expensive of the cedar species. It’s native to the eastern United States, where it rises in U.S. Department of Agriculture zones 2 through 9. Western redcedar (Thuja plicata) rises from the Pacific Northwest at USDA zones 6 though 8. It resists rot for 10 to 25 years and is not as immune to pest attacks as eastern red cedar. Northern white cedar (Thuja occidentalis) resists termites and lasts about five to 15 years. It’s often used for making outdoor furniture and rises in USDA zones 2 through 7 at the northeast United States. Cedar sorts are more likely to be available in their native areas and at a more cost-effective price.