Examples from the Web for heartwood
Nearly all the larger trees in the Fuegian forests have the heartwood decayed, and are worthless as timber.The Land of Fire|Mayne Reid
Heartwood does undergo changes, but they are gradual and almost entirely independent of the seasons.
A stub left on a trunk or large branch does not heal, but soon begins to rot at the end where the heartwood is exposed.Apple Growing|M. C. Burritt
It is true that sapwood will not resist decay as long as heartwood, if both are untreated with preservatives.
Sapwood, as a rule, shrinks more than heartwood of the same weight, but very heavy heartwood may shrink more than lighter sapwood.Seasoning of Wood|Joseph B. Wagner