Douglas-fir (Pseudotsuga menziesii L.) is a tree species that could compensate for a possible shortage of spruce in Slovenia in the future, as it has comparable physical and mechanical properties and better natural resistance. In order to make the best use of the properties of this tree species, we determined the influence of juvenile period on selected physical and mechanical properties of solid wood and their variability on samples from the Ravbarkomanda and Pečovnik sites. By measuring annual ring widths and the proportion of latewood, we confirmed the trend that ring widths decrease with distance from the pith. The proportion of latewood increased with distance from the pith and significantly influenced the increase in wood density. Wood density increased most between the 20th and 30th growth rings, i.e., at the age of the cambium, and less at older ages, and variability was also lower. The bending strength and stiffness of Douglas-fir wood, as determined by a standardized static 3-point mechanical test, increased with distance from the pith, as did wood density. Fragile and simple bending fractures were confirmed in juvenile wood and long-fibre fractures mostly in adult wood samples with higher cambium age. With distance from the pith, the compressive and shear strength and Brinell hardness of the wood increased significantly along the grain. When testing properties transverse to the grain, the differences were smaller and characteristic only between the earliest juvenile period (
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