When Northern Europeans converted to Christianity, they kept the custom of the evergreen - because it stayed green and alive in Winter. This practice became part of the Christmas celebration. They also liked to adorn the tree with apples and candles - now our ornaments and lights.
Jeremiah, Chapter 10, verses 2 through 5 read, "This what the Lord says: "Do not learn the ways of the nations or be terrified by signs in the sky, though the nations are terrified by them. For the customers 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 melon patch, their idols cannot speak; they must be carried because they can not walk. Do not fear them; they can do no harm nor can they do any good."
I found that passage quite intersting when I came across it. It immediately reminded me of our Christmas trees. Certainly food for thought.
I forgot to mention - if you want to put candles on your tree for old times sake, make sure your insurance is paid up. I understand that the old European winter festival also mysteriously coincided with a lot of house fires :)