how to store christmas tree without taking it apart

Well, if you're not taking the tree apart, there's not a lot of options. You could try wrapping it in a big sheet or tarp, or maybe try hanging it from the ceiling by some ropes. But if you're really looking to save some space, I would recommend taking it apart and storing it in the attic or basement. That way it'll be out of the way and you won't have to worry about it taking up too much room.