Oak is the only tree with naked-eye ray lines in its wood

Evidence

The outer heartwood of the trees of white oak species is especially decay resistant, lasting more than a century, while the center, or inner heartwood, can begin to decay in 50 years. By this time, the outer wood of the stump starts to develop vertical fissures that get bigger as the stump ages. Hollowed-out white oak stumps can be identified by their visible ray lines that run from the outside of the stump toward the center, cutting across the annual growth lines (S.8). These ray lines can also be seen as vertical lines when carving through the bark into the outer wood of an oak trunk (S.9). Oaks are the only trees that have ray lines visible to the naked eye. — Tom Wessels, Forest Forensics, 150

Categorization

• DEFINE: Defines ray lines as a species-distinguishing wood feature.
• SHARE: Oaks-only ray lines is a crisp field detail for a tree/woodworker friend.