Sapwood is the younger, living layer of wood in a tree, located just beneath the bark. If you imagine a tree trunk as a series of rings, the sapwood is the outer band of lighter-colored wood that's still actively working. This is where water and nutrients travel up from the roots to the leaves, like plumbing pipes running through the tree.

When you look at a freshly cut log, you can often see two distinct zones: the pale sapwood on the outside and the darker heartwood at the center. The sapwood is softer and lighter because it's still alive and full of moisture, while the heartwood is older, denser, and no longer transports water.

Carpenters and woodworkers pay attention to sapwood because it behaves differently than heartwood. It's more vulnerable to rot and insects since it contains more moisture and nutrients that bugs find appealing. For building projects that need to last, craftspeople often prefer heartwood. But sapwood isn't useless: it's perfectly fine for many purposes, and in some trees, like maple, the sapwood is actually prized for its light, clean appearance in furniture and flooring.

As a tree ages, its inner sapwood gradually transforms into heartwood, becoming part of the tree's strong central core.