There are many symbols of the season, but the Christmas tree is the most iconic.
Most skeptics know that the tradition of taking in a tree for the winter pre-dates Christianity’s arrival in Europe by hundreds of years. Many pre-Christian cultures used to cut boughs of evergreen trees in Winter, move them into the home or temple, and decorate them (see Jeremiah 10:1-5). This was to recognize the winter solstice — the time of the year that had the shortest daylight hours, and longest night of the year. This occurs annually sometime between Dec-20 to 23; most often, it is Dec-21. As the solstice approached, humans noticed that the days were gradually getting shorter; many feared that the sun would eventually disappear forever, and everyone would freeze. But, even though deciduous trees, bushes, and crops died or hibernated for the winter, the evergreen trees remained green. Naturally, they seemed to have magical powers that enabled them to withstand the rigors of winter.
[For a further explanation of the celebration of the solstice and how it relates to the Christmas holiday, please see The Jesus Myth and Christmas Politics]
Trees play important roles in mythology as natural objects rooted in the earth and reaching up to the sky. They become symbols of communication between the world of humans and that of divinity, as in the case of the world tree, Yggdrasill. Trees are also places of sacrifice. Thus Jesus hanging the cross (often referred to as a tree) becomes the new fruit to replace the sinful fruit of the forbidden tree in the Garden of Eden. The effigy of Attis is hung on a tree, symbolizing death and resurrection. Odin hangs willingly on the world tree to learn the mysteries of the runes. The body of the murdered Osiris is discovered in the column that had been a tree. The Buddha finds enlightenment through resisting temptation under a tree. 
“The custom of decorating an evergreen tree goes back to the pre-Christian period of ‘raw nights’ (December 25 to January 6) when people would hang green branches in their houses and light candles to keep evil spirits at bay”. Going back even farther, we discover just why the fir tree, or evergreen tree, was chosen to represent Christ and why the ‘heathen’ held this tree sacred. As an evergreen, the pine symbolizes immortality…It is an attribute of the Greek god, Bacchus, and an emblem of Jupiter, Venus, and Diana”. 
In ancient Rome, the immortal pine was used to celebrate the spring festival of Arbor intrat. Each year on March 22, members of the cult of Cybele cut down a pine tree and carried it to the Palatine temple. There, it was bandaged, wreathed with violets, and mourned as if it were the body of Attis, son of Cybele, who, disturbed by his mother’s attentions, had castrated himself and died beneath a pine tree. His soul was believed to have found refuge in the pine and his blood caused violets to spring up around it. Three days later, he was miraculously restored to life. 
Even the Christian Bible and the Jewish Tanakh record the “heathen” origin of the Christmas tree. Take a look at Jeremiah 10:1-5:
“Hear what the LORD says to you, people of Israel. This is what the LORD says: ‘Do not learn the ways of the nations or be terrified by signs in the heavens, though the nations are terrified by them. For the practices of the peoples are worthless; they cut a tree out of the forest, and a craftsman shapes it with his chisel. They adorn it with silver and gold; they fasten it with hammer and nails so it will not totter. Like a scarecrow in a cucumber field, their idols cannot speak; they must be carried because they cannot walk. Do not fear them; they can do no harm nor can they do any good”
Unbeknownst to most religious observers, “God” is actually against the Christmas tree. But that doesn’t stop millions of people from putting up Christmas trees (“God” is so easy to ignore).
Today, the Christmas tree has become accepted by most Christians, by people of other faiths, and for those who do not follow an organized religion. It has become a popular late-December tradition and part of our present-day culture.
Thanks for reading,
- Leeming, David; “The Oxford Companion to World Mythology”, Oxford University Press, 2005
- Bruce-Mitford, Miranda. “The Illustrated Book of Signs and Symbols”, Montreal: Readers Digest, 1996.
- Tucker, Suzetta. “ChristStory Christmas Tree Page.” ChristStory Christian Bestiary. 1997. http://ww2.netnitco.net/users/legend01/xmastree.htm ( 1 Dec. 2011).