This paper reviews recent literature on the formation of heartwood and on the components that affect natural durability. It includes discussion about the function of heartwood in living trees, factors influencing the natural durability of heartwood, the process of heartwood formation, and variations in heartwood quantity and quality. Heartwood formation is a regular occurrence in tree stems, and heartwood may have many different properties from sapwood, including natural decay resistance. A greater understanding of the heartwood formation process could allow control of heartwood production. Recent research involving enzymatic analyses have provided valuable insight into the biochemical processes involved in heartwood formation. Further study of the role natural durability plays in living trees would help to bring together many of the disparate strands of research relating to heartwood
