Christmas trees originated from the pagan customs of the powers worshiping nature, not necessarily nature itself. Ancient pagans believed that there are spirits around us even within the sacred trees, which they appeal to and sacrifice. They make these trees the center of their religious ceremonies.
It is present in many ancient mythologies, like oak for Celtic druids. They are banyans in Hinduism. They have sycophants in Egypt. Some are more mythological than realistic. In Norse mythology they have the Yagdrashil or World Tree which connects nine places. He also has knowledge of good and evil in Judaism and Christianity.
Evergreen trees which are the most commonly used Christmas tree grow, save life and survival because these are the kind of trees that survive during winter. Decorating the Christmas tree comes from the tradition of hanging written wishes and prayers to win favors for the spirits living within it. The same goes with the superstition to knock on wood, to establish a connection with the soul of the tree.
We now display a Christmas tree in the middle of the living room or in the center of the city, while we celebrate Christmas around it like the ancient pagans did.