In the European Middle Ages, the most popular tree for building was the oak. There are hundreds of species of oak found all over the world, but mostly in the northern hemisphere. Some are bent, some are straight, and half are evergreen. The wood is tight-grained and very strong and has little tendency to warp or crack. The Common Oak, Quercus Robur, rarely grows straight naturally and so was employed in early bent-cruck style framing and in later curved truss- and wall-bracing. The prized species is the White Oak (Quercus Alba), that can be found tall and straight. Spike Carlsen describes the balanced qualities of the oak tree: “It is not too hard, not too soft, not too stiff, yet not too pliable; the grain falls somewhere between fine and course, it has interesting grain patterns, but the grain is not so interesting as to be distracting “. It was thus admired not only for its utility in construction, but also for its intrinsic beauty.
European lore has it that oak trees are struck by lightning more than any other tree. This explains its connection with the weather gods. In the old Slavic culture, the god of thunder and lightning was known as Parem, in the Norse, Thor, in the Saxon, Donur, and in the Celtic tradition Taranis. Also associated with forests and trees were the gods of the hunt, such as the horned god Hearne and the mystical forest entity known as the Green Man. Besides its beauty and metaphysical qualities, the oak tree was a symbol of strength and even patriotism. It is the official tree of Germany, The United Kingdom, and the United States.