Characteristic of wood is that its behavior is strongly orthotropic due to the internal structure of the material and dependent on moisture and temperature. In addition, the material is characterized by a strong variation of the properties in the radial direction.  Another important property that affects the behavior of wood is spiral grain, causing the direction of the fibers to deviate from the longitudinal direction of the tree. It is hardly possible to assess spiral grain in the woods, no rejection of severe spiraled trees are done before the log arrives into the sawmill. If a method for on site rejection is available, and the severest spiraled trees, 2-10%, could be avoided in the shipment to the sawmill substantial money could be saved in the forest industry. The causes of spiral grain have been thoroughly discussed through the years and the debate about the environmental and genetic impact on the phenomenon is still not settled. We present evidence for a direct effect of wind on the degree of spiral grain. We also present evidence for a putative thinning effect on spiral grain that is probably connected to wind. Additionally we also present evidence for a strong genetic impact on the formation of spiral grain in conifer trees. In another study mechanical properties such as shape stability has been investigated for the same trees. In some of the logs it may therefore be possible to quantify the relation between spiral grain and distortion in sawn timber.