Christmas trees, to be really strict about it, shouldn't be decorated until Christmas Eve, and then left up until 12th Night--but this is now a very commercial activity, we can't expect every one to agree. So let a lot of trees go, bc we, here in Katrina land remember the 2005 Christmas and there were no trees, or very few. It was a sad and yet joyful Christmas in so many ways.
Personally, our guy, Adrian, goes to North Carolina the week before Thanksgiving. He knows what tree we want, 9', narrow, and brings us a great tree every year, sometimes it still has snow in it. It's left up until 12th Night, the first night of Carnival--ending on Mardi Gras--every place else misses that connection except for a very few people. We start the party on the first Sunday of Advent, and progress through the whole season until Easter. It's more European than the rest of our country, but we LOVE it.