“The groves were God’s first temples”, the saying goes, and in countries as widely separated as Mexico and India, Madagascar and Sweden, tree worship was one of the first religions of the inhabitants. It surrounded the Israelites in Palestine, prompting the patriarchs to issue the command, “Thou shalt not plant thee a grove of any trees.” (Deut. Xvi. 21.) The fig tree was sacred in Egypt, Japan, and India. The Romans, too, held it in high regard, for they believed that with its overhanging branches it had stayed the floating basket that contained the infant twins, Romulus and Remus. Most of the sacred groves that decked the seven hills of the Imperial City were of oak, and in far away Britain the same tree was worshiped by the ancient Druids.
The “knock on wood” superstition is said to date back to the age of pagan woodland gods as well, when oak, ash and rowan were sacred trees whose deities would come to the assistance of the knocker.
It was the common belief that good or bad spirits were shut up in the giants of the forests, where sometimes they talked and moaned and sang, always exerting a benign or evil influence upon man. It became necessary, then, to appease the wrath of the tree spirits if they were evil and praise them if they were good. Many of the customs practiced today are remnants of these widespread prehistoric rites.
As recently as the early 20th Century, there were many reports in Kansas of trees suddenly dying without apparent cause after having been used as gallows for lynchings. Many are said to have never bloomed again after being used for hangings.
Click HERE to read about Oak Tree Superstitions.