My recent post makes me wonder what makes a Christmas tree symbolic at Christmastime. And I wish to thank Titov for giving me these great ideas about the significance of Christmas tree to our Christian faith. He wrote this under my comment box and I wish to repost it for everybody to know.
Here are the reasons why we have Christmas tree:
1.More and more frequently families are blessing their Christmas trees. It is good to remind children that "the tree" relates to many aspects of our faith. For example, we are reminded that our first parents were not allowed to eat from one tree, and that Christ paid the great price for our redemption by hanging on a tree (cf. Acts 5:29-32).
2. And it should be noted that Christianity has externally borrowed from pagan customs -- e.g., wedding rings, bouquets, brides wearing white, Christmas trees, and Easter eggs -- but has transformed their interior meaning to conform with Christ. Just as the Church baptizes pagans and makes them into Christians by God's grace, Christians can give old customs good, new, and richer meaning, e.g., Christmas and Easter replaced pagan feasts associated with winter and spring, respectively.
3. Pope Gregory I, who reigned from 590-604, said, "Let the shrines of idols by no means be destroyed. Let water be consecrated and sprinkled in the temples, let altars be erected...so that the people, not seeing their temples destroyed, may displace error and recognize and adore the true God....And because they were wont to sacrifice to devils, some celebration should be given in exchange for this...they should celebrate a religious feast and worship God by their feasting, so that still keeping the outward pleasure, they may more readily receive spiritual joys," quoted in John Greenway's Folklore of the Great West (Palo Alto, California: American West Publishing Company, 1970), p. 384, emphasis added.
4. On the winter solstice (December 21), pagans celebrated the feast of "Sol Invictus," the "inconquerable sun" that waned in winter-shortened days but was not "overcome" by the darkness. Christians chose to keep the natural timing of the holiday and replace its pagan meaning with the Christian message, the inconquerable Son (Jn. 1:5).
5.There are many different stories which attempt to explain why we use a tree at Christmas. For instance, St. Boniface in the eighth century gave the balsam fir tree to the Druids in place of the oak tree, the symbol of their idol. He said, "The fir tree is the wood of peace, the sign of an endless life with its evergreen branches. It points to heaven. It will never shelter deeds of blood, but rather be filled with loving gifts and rites of kindness."
6.The Jesse tree tells about Christ's ancestry through symbols and relates Scripture to salvation history, progressing from creation to the birth of Christ. The tree can be made on a poster board with the symbols glued on, or on an actual tree. For further information read, Advent and Christmas in a Catholic Home. 
7. The Jesse tree reminds us of Jesus' Davidic ancestry (cf. Mt. 1:1). For a greater understanding of the relationship between the house of David, Jesus, and the Catholic Church's divine origin, see CUF's FAITH FACT: "Rock Solid: The Salvation History of the Catholic Church."
God bless us all!:)