The green trees were already in the garden of Eden, and green was symbol of life always.
But the origin of the Christmas tree is perhaps in Germany. It was called "PARADISE TREE"= the people fetched once ay year their little paradise in there houses with a tree, hey they believed in the paradise! It is a christian tradition out and out therefore.
BTW A direct connection between the "Christmas tree" and old Germanic "pagan? "Yul" -festival is not traceable
http://www.history.com/topics/christmas/history-of-christmas-trees
http://www.zeit.de/wissen/geschichte/2012-12/geschichte-weihnachtsbaum
http://www-weihnachten.com/weihnachten-infos/christbaum.htm
More details from these article I will present tomorrow, if the angels want.
1419 - 1st tree deployed at bread shop in Freiburg with nuts and fruits, they could be