Heartwood 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.
... large in height, spread and trunk diameter. They are attractive and stately in appearance and it is the hardiest member of the walnut genus as its native range extends well into Canada. The bark is gray in color and the wood is soft. Heartwood decay is common in old trees, although they may reach great age. The species has a rather restricted range within the Eastern states, but it occurs naturally as far west as eastern Kansas and Nebraska. In Missouri, its growth is confined largely to ... — Northern Nut Growers Association Report of the Proceedings at the 41st Annual Meeting • Various
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