three files easy to print:

1. Tree/Tree plus: 0% infill is best, 0.2 mm layer height, No supports required. you can add stop and change color command in between for colorful charismas tree.
2. Star: 20% infill, 0.1-0.2 layer height, supports needed. 
3. Joint: 20% infill, 0.2 layer height, No supports needed. used to joint the star to the tree. or you can just use super glue instead.

Stretch down the spirals using your hand force as far as you can. the spiral will restore its position after your release it but it will cover the whole tree now. you might apply more force to get to your perfect shape.

Remove supports from the star, attach star to the tree using the join.