Where did the custom of Christmas trees originate?

The idea for the Christmas tree, as well as the other thought-to-be Christmas holiday practices, including exchanging gifts, "nativity" scenes, and even flying reindeer, predate Christianity and the celebration of Christmas itself (which some sources claim was instituted by a pope in the fourth century of the common era in order to draw the early Christians' focus away from the then widely practiced pagan winter celebration of Solstice and Yule and to hopefully substitute new meanings to be assigned to those same pagan rituals.) Pagans then and now celebrate the lowest point in the path of the sun's travel, the darkest and coldest days of the year, by bringing in evergreens to either brighten up their indoor space with signs of new life or to offer a warm space for good spirits to come indoors and warm themselves up. Also, the prickly leaves of evergreens would catch any evil spirits as they tried to enter the home. Other faiths, including those of many Native American tribes also have similar practices that predate Christianity by many centuries.