The wood of each tree species varies with the environmental conditions under which the trees grow. Under certain conditions wood is formed that is distinctly abnormal in its structure and properties. One such type of abnormal wood is the so-called compression wood formed on the lower, or compression, side of branches and of leaning tree trunks of all coniferous species. Other names applied to compression wood are hard grain, timber bind, pressure wood, Rotholz (German), Druckholz (German), bois rogue (French), and tenar (Swedish).

The purpose of this bulletin is to present a discussion of the appearance, occurrence, and certain physical and mechanical properties of compression wood. With such information this type of abnormal wood may be identified and eliminated from those uses in which it is particularly disadvantageous. In addition, information is presented on the growth conditions under which compression wood occurs so that by suitable forest-management practices it may be possible to reduce materially the amounts of compression wood in many stands of timber.