This is an interesting article: http://www.gomemphis.com/mca/home_and_garden/article/0,1426,MCA_523_1818045,00.html A little worried it would disappear from that site as they preserve server space, I've taken the liberty to copy the most important section - which involves some interesting speculation about why oak trees have such a powerful symbolic meaning ni pagan worships: "Scientists have proven that oaks are struck by lightning more often than any other tree species - and they literally explode. No wonder ancient Greeks believed the thunder god Zeus lived in oak trees, and though his temples ruins remain the tree that they honored has long since decomposed. "One reason for the explosion is that old oaks often have water-filled cavities in the central heartwood of their trunks. When the tree is struck with a 50,000-degree bolt of lightning, the water expands instantly and the tree explodes like a bomb. The lightning then travels down the oak and out through its extensive root system. A mature oak can produce a root zone spreading out 60 feet from the trunk. The lightning travels along these roots to strike unsuspecting victims standing well beyond the canopy limits. "Oaks once blanketed much of Europe and Britain with one dominant species, Quercus robur, sometimes called the holm oak. This is a survivor of the last ice age and can be found growing eastward into Russia. Named robur from the Latin for strength, it is sometimes called the English oak despite its far ranging origins. "This tree became the symbol of England at one point and figured largely into the expansion of her empire. The wood was used for keels and ship sheathing for their extensive fleet. These immense timbers were still useful in the 20th century during World War II when the oak ribs of one of Lord Nelson's flagships shored up Winston Churchill's bunker. "This oak also figured into the ancient world of the druids, a priestly class of tribal Celts. They recognized old oak trees as the abodes of powerful nature spirits. They often built their stone circles or "henges" at the darkest part of the forests which have long since been cleared for farming. "Roman authors who came upon these forest henges described them as grizzly places where the trees were decorated with bones, hair, hides and other unsavory tokens. Fires burned day and night creating a fog of smoke. Huts of the priest guardians surrounded the area lest someone accidentally wander in to desecrate this hallowed ground. "Druids also forbade worshiping under roofs which separate one from spirit tree canopies overhead. Some believe that the tall arching ceilings of the early cathedrals bear a striking resemblance to the network of soaring branches of these forest oaks. This similarity may have eased the concerns of former forest worshiping pagans reluctant to enter a religious building. "Druid sanctuaries often were connected to the very oldest oak in the forest. Through the rustling of its leaves and twigs, prophecies were whispered to the priests. These became oracle oaks, considered so sacred that anyone who ventured into these haunts of the druid elite would be executed. Should one snap a twig or cut this tree, he would be flayed and his skin used as a bandage. Naturally the dark dells of the forests became haunted places to be avoided at all costs. "When the old pagan religions died out, the ancient oaks were no longer protected. In England and on the continent the forests were felled as fuel for a swelling population, and to build both houses and ships. The land was turned over to field and pasture and the trees never grew back."