Should I use cedar or pressure-treated lumber for raised beds in NB?

Cedar is the recommended choice for raised garden beds in New Brunswick, especially for growing vegetables and herbs, because it is naturally rot-resistant without chemical treatment and does not introduce preservative compounds into the soil where food plants grow. Eastern white cedar, widely available from NB lumber suppliers, contains natural oils (thujaplicins) that resist decay for 10-15 years in ground-contact applications — more than enough lifespan for a raised bed that can be rebuilt when it eventually deteriorates.

The concern with pressure-treated lumber centres on the chemical preservatives used to prevent rot. Modern pressure-treated wood in Canada uses alkaline copper quaternary (ACQ) or copper azole (CA-B) preservatives, which replaced the arsenic-containing CCA treatment phased out for residential use. While ACQ and CA-B are considered safer than CCA, they still leach copper compounds into surrounding soil, particularly during the first few years. Health Canada has not banned pressure-treated wood for garden use, but many NB gardeners prefer to avoid the question entirely by choosing cedar, especially for food production.

From a cost perspective, pressure-treated lumber is significantly cheaper. A 2x10x8 pressure-treated board costs roughly $12-18 at NB building supply stores, while the same size in cedar runs $25-45 depending on grade and availability. For a standard 4x8-foot raised bed, the material difference is approximately $50-100 between the two options. However, cedar's natural beauty — its warm golden colour that ages to an attractive silver-grey — adds aesthetic value to your garden that stained or green-tinted pressure-treated wood cannot match.

If you choose pressure-treated lumber to save money, line the interior walls with heavy-duty plastic sheeting (6-mil poly) to create a barrier between the treated wood and the growing soil. This prevents direct contact between preservative-leaching wood and root zones. Use stainless steel or coated screws rather than standard galvanized fasteners, as the copper in ACQ-treated wood accelerates corrosion of regular galvanized hardware. Pressure-treated wood does offer superior longevity — 20-25 years versus cedar's 10-15 years — so it may be the better choice for permanent ornamental raised beds planted with non-edible flowers and shrubs.

For the best longevity from cedar raised beds in NB's Maritime climate, use 2-inch thick boards (actual 1.5 inches) rather than 1-inch boards, which deteriorate faster. Set the beds on a gravel base rather than directly on soil to improve drainage and reduce wood-to-soil contact rot. Avoid painting or staining cedar — the natural oils provide adequate protection, and sealants can trap moisture inside the wood and actually accelerate decay. A well-built cedar raised bed using 2x10 or 2x12 boards, corner posts, and stainless steel screws will serve a NB garden reliably for a decade or more.

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