Christmas tree.

An evergreen Christmas Tree, decorated lavishly with ornaments, tinsel, and lights, is one of the most popular and prevailing image of Christmas. There are various legends about how the tree represents the enduring message of Christ, but in actual fact, as with many of the accepted and generally unquestioned traditions of Christianity, this too was lifted from the already existing Pagan customs and conveniently incorporated as an integral religious symbol.

It was customary for the Pagans in the Northern Hemisphere to celebrate the Winter Solstice. This is the shortest day and longest night of the year, generally falling on 21 or 22 December, and the Pagans believed it to be the turning point at which the Sun God began to recover once more from the sickness that had plagued him in the earlier months and which had brought Winter to the land. Such an event, of course, had to be celebrated, and the celebrations were marked with decorations of evergreens like pine, spruce and fir being put up over doors and windows - the evergreens had admirably withstood the onslaught of winter unlike other plants, and so hopefully were capable of withstanding and warding off any attentions from unwanted elements like witches, evil spirits and so on. This was one reason for so honoring them, and, secondly, their greenery symbolized the other plants/crops/means of livelihood that would, thanks to the recovering Sun God, soon spring back to life, and make overall existence easier for everyone.

This was the general philosophy that was followed by the Celts, the Goths, the Vikings, the Early Romans and the Egyptians, amongst others of the Ancient World. The Egyptians, worshippers of the Sun God Ra, of course used the more easily available green Palm leaves instead of pines. The Romans had a really grand celebration known as the Saturnalia, where the entire city turned out to pay homage to their God of Agriculture, Saturn, and have a generally riotious time. All Roman houses and temples were decorated with evergreen boughs during Saturnalia.

Later on, as mentioned, the Christians adopted the custom. From being a pagan symbol of everlasting life, the Christmas tree went on to become the symbol of the Trinity.

But the tradition of a decorated Christmas Tree as we know it now is considered to have been started in the 16th century by the Protestant Reformer Priest, Martin Luther. Apparently, on one of his nightly walks, he had stopped to admire the sight of stars shining brightly through the branches of the towering evergreens between the evergreens and thought his family should share in the wonder of the sight. So, instead of logically summoning them outside, he later had a tree cut and brought indoors, where he attempted to recreate the effect by fixing candles in candle-holders on its branches. This was the start of having indoor Christmas trees.

Much later, when many of the Protestant followers of Martin Luther migrated to Pennsylvania, they brought the tradition of the Christmas tree to America.

It didn't gain wide-spread hold in America right away though. The Puritans, suspicious as always and rightly in this case, wanted to have no truck with 'heathen customs' - this included a strong oposition to singing carols and anything that might remotely smack of enjoyment and 'desecrate' the holy event. Actually the Puritans were opposed to celebrating Christmas on 25th December too and even managed to get the General Court of Massachusetts pass a law that made it a penal offense - people could actually be arrested for singing or decorating their homes!

However as more and more new arrivals from Europe and the rest of the world came to settle in America, bringing with them their own notions of how Christmas ought to be celebrated, the Puritans gradually loosened up, and by the 1840s Christians were going to prisons for reasons that usually had little to do with religious fervor.

Meanwhile, in England, the Christmas Tree received official sanction, again with German influence, when the German-born Prince Albert, the husband of the very popular Queen Victoria, arranged for a family Christmas tree in 1846. With the Royals setting the fashion trend thus, the rest of the country was quick to follow suit.

The Christmas Tree soon became a common sight at Christmas, with the wealthy outdoing each other in setting up lavishly decorated, floor-to-ceiling Christmas trees. It was only a short step from here to start setting up the trees outside in public.

Initially things like apples, candies, nuts, pop corn, berries and home-made decorations were used to adorn the Christmas Tree, but these were later joined by specially made, beautifully crafted crystal ornaments, bells and, with the advent of electricity, with strings of twinkling lights. Even these decorations have by now come to gain a symbolic meaning in the Christian religion - the apples and crystal balls representing the fruit of redemption, the lights signaling the triumph of good over evil, the bells ringing in the joys of life, and the star or dove on top epitomizing the Holy Spirit.

But whatever the significance anyone wants to put on it, one thing is for sure - a Christmas tree certainly adds to the season's aura.

sidenote: also symbolic to shiva, the kundalini and it goes on and on.

Here's another breif summary: The symbolic meaning of Christmas trees originates in pagan culture where the evergreen represents life, rebirth, and stamina needed to endure the winter months. Scandinavian and Norse traditions honored the winter solstice (December 25) by decorating evergreens.  At this time fir trees were also burned to commemorate the life that stirs even in the most frigid grips of winter.  These traditions also marked the end of the old year and the beginning of a new year.
Pagan lore indicates the time between December 25 until about early-mid January are some of the coldest days of the year.  It was believed evil spirits were at their strongest during these months.  To thwart the nasties, evergreens were brought into the home as symbols of protection.  These evergreens were alight with candles, the idea here was to “light up” the darkest, coldest conditions and thereby shoo away naughty spirits.
 It wasn’t until about the nineteenth century that we find Christianity absorbing the bright, cheery symbolism of the Christmas tree.  The Christians had long held the fir as a symbol of the Tree of Life.  Early Christians knew their symbolism well, as they added candles and apples to their Christmas firs.  These candles represented the light of Christ.  The apples symbolized knowledge which spawned man’s original sin according to Christian belief.  Here we see the light of Christ absolving the “fall of man” within the immortal symbol of the Christmas tree.