Tree pose is a basic balancing posture that can take on new meaning during the holidays. Now, I'm not suggesting that you drape yourself in tinsel and wear a star on your head; however, you might consider the comfort and iconography of trees during the winter season and, of course, within the Christmas tradition.
Moreover, embrace the steadiness of a tree with deep roots; recognize a tree's ability to weather all seasons and adapt to its surroundings, and use the asana as an opportunity to pay homage to all the favorite trees in your lifetime. Perhaps you had a treehouse as a child or sat beneath your own "giving tree," to collect your thoughts and escape the world.
In order to make the holidays more joyful, spend time honoring the season outdoors. I live in one of the coldest climates of them all, Boston, but I am vigilant about getting outside every day. The fresh air and emphasis on natural surroundings- during a time that tends toward commercialism and material possessions- will help keep your spirits up and body active. The fringe benefit, of course, is that a 15-minute walk snuck into your lunch break or walking with your children to the bus stop in the morning helps stave off the extra calories you might be consuming in cookies, candies, and other holiday fare.
Finally, if you do celebrate Christmas and decorate a traditional tree each year, let the symbol of the season also be an inward symbol of your own yoga practice. We don't practice yoga simply for its own sake, on a mat, in a studio, isolated from the world. We practice yoga so that we're better able to embrace, honor, and experience the world. Trees included. All year long.