Heartwood
/HART-wood/🔬 Anatomy● Basic
Also known as: duramen
Heartwood is the central core of the trunk composed of dead xylem cells that have been chemically transformed with tannins, resins, and other substances that darken the wood and make it resistant to decay. While it no longer conducts water (that role belongs to the outer sapwood), heartwood provides critical structural support. The transition from sapwood to heartwood varies by species — some produce distinct heartwood, others do not.
Etymology
From Old English heorte (heart, core) + Old English wudu (wood)
Example
“The black walnut was prized for its dark heartwood, which is highly valued in fine furniture making.”