When did Christmas Trees become part of Christmas celebrations?

Evergreen trees and wreaths have been used as symbols of eternal life since the ancient times of the Egyptians, Chinese, and Hebrews.

After the coming of Christianity, evergreens were still used in Scandinavia, to scare away the devil.

In the Middle Ages, the Christmas tree, decorated with candles and wafers (symbols of Christ and the Host), became popular, as did the gaily decorated wooden Christmas pyramid.

By the sixteenth century, the two objects merged into what we now know as the Christmas tree.

By the nineteenth century, the Christmas tree was popular across Europe and the United States.