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Dead, central wood of trees. Its cells usually contain tannins or other substances that make it dark and sometimes fragrant. Heartwood is mechanically strong, resistant to decay, and less easily penetrated by wood-preservative chemicals than other types of wood. One or more layers of living and functional sapwood cells are periodically converted to heartwood.
This entry comes from Encyclopædia Britannica Concise. For the full entry on heartwood, visit Britannica.com.