My discerning of a Christmas tree is based in the book of Genesis 3, which outlines the fall of man.
The first commandment or legislation of God to man was that pertaining environment as per Genesis 3: 2-3; The woman said to the serpent, “We may eat fruit from the trees in the garden, but God did say, ‘You must not eat fruit from the tree that is in the middle of the garden, and must not touch it, or you will die.'” end of quote.
Now, after being deceived by the serpent, Eve gave in and broke God’s first commandment. Hence verse 22 of Genesis; And the LORD God said, “The man has now become like one of us, knowing good and evil. He must not be allowed to reach out his hand and take also from the tree of life and eat, and live forever.”
So, from above bible quotations, and Christmas being celebration of restoration of relationship between man and God. Then Christmas tree is a reminder of the fall of man from God.