Heartwood

[hɑ:twud]

Definition

(noun.) the older inactive central wood of a tree or woody plant; usually darker and denser than the surrounding sapwood.

Edited by Estelle--From WordNet

Definition

(n.) The hard, central part of the trunk of a tree, consisting of the old and matured wood, and usually differing in color from the outer layers. It is technically known as duramen, and distinguished from the softer sapwood or alburnum.

Typed by Ferris