The Christmas Tree
Was originated in Germany when a small offshoot stood between the branches of a fallen oak.  It was a young firtree and a sign of everlasting life was manifested by its evergreen specie.  Candles on it represented the Light of the World.  Gifts under it represented God's gift of his Son to the world.  Later, other decorations were made and put on the tree.

Holly
Used to make wreaths at Xmas, symbolized the crown of thorns, and the berries, drops of blood.

Xmas Greens
Put around to give a festive look.  Evergreen gave thoughts of long life.

Poinsettias
Just a popular flower that can flourish at Christmas time.

Yule Log
A symbol of warming light, and safely.  Its steady fire was sign of good luck.

Mistletoe
A kiss under the mistletoe is a symbol of peace and an assurance that mistletoe can cause no more sorrow as it did in the ancient myths.  Hanging it over a doorway brings romance.