Decay Resistance
The natural ability of certain wood species to resist fungal decomposition without chemical treatment, due to extractive compounds in the heartwood.
In-Depth Explanation
Decay resistance is determined by the concentration and type of extractive compounds deposited in heartwood cells as the tree matures. These extractives are toxic or repellent to the decay fungi that break down wood cellulose and lignin. The USDA Forest Products Laboratory classifies species from very resistant (black locust, old-growth redwood) to non-resistant (maple, birch, most sapwood). Only the heartwood of resistant species provides significant decay resistance; the sapwood of even the most durable species is vulnerable. For outdoor applications where natural durability is preferred over chemical treatment, selecting the appropriate species and ensuring heartwood content is critical.
Usage Example
We chose western red cedar heartwood for the raised garden beds because its natural decay resistance means no chemical treatment near vegetables.