Sapwood
The lighter-colored outer layer of wood beneath the bark that actively transports water and nutrients in a living tree, generally softer and less durable than heartwood.
In-Depth Explanation
Sapwood forms the physiologically active outer rings of a tree trunk, serving as the pipeline for water and minerals moving from roots to leaves. It is lighter in color than heartwood because it lacks the extractive compounds that darken and preserve the inner wood. In species like walnut and cherry, the contrast between pale sapwood and dark heartwood is dramatic, affecting both aesthetics and market value. Sapwood is more susceptible to decay and insect attack because it contains starches and sugars that attract organisms. For outdoor applications requiring natural durability, heartwood is preferred, while sapwood is suitable for interior use.
Usage Example
The walnut board had two inches of pale sapwood along one edge, which I trimmed off to keep a consistent dark color.