The Christmas tree as we know it today grew out of German traditions from the Middle Ages. One tradition which has a clear lineage to our modern Christmas tree is that of the Paradise Play.
Paradise Plays were dramatizations put on by the Church to teach the story of Adam and Eve. Most people would not have been able to read at that time, so performances like these were how people learned about religion. The creation story, the story of original sin, helped people to understand why they needed Christ’s salvation.
The Play would have started with the fall of rebel angels from heaven. I imagine this to have been a very exciting beginning, with a violent battle between good and evil. The creation story follows, with the temptation and fall of Adam and Eve.
There were very few props; the evergreen juniper tree was used to represent both the tree of life and the tree of knowledge from the Garden of Eden. Red apples were hung from the branches as symbols of the fruit which tempted Adam and Eve. As these plays gained in popularity many Germans began bringing their own trees indoors.
The apple bearing tree became an established symbol of Christmas through the Feast of Adam and Eve which was held on December 24. The Old Church chose Christmas Eve for the Feast to show Christ as the second Adam, returning to Earth to heal the sins of the first Adam by sacrificing his life. Paradise Plays, with the evergreen tree at the center of it all, became a large part of the holiday tradition.