I've been hearing all about this Christmas tree thing, but I still don't know how to get one. I also heard that today is the last day that you can get one, so I was hoping that I can get one before the Christmas update ends.
Christmas trees are completely random spawn just like any other ground obstacle. (Only spawning when you aren't playing )
From playing on two different accounts: I noticed that my lower level account spawned 4 Christmas trees while my high level account only spawned 2 during this seasonal theme. In addition, the lower level account had much more room free to spawn which may have improved my chances for spawning them.