https://teachbesttech.org/the-modern-christmas-tree/

and modern Christmas tree cover it with plastic. Do not remove the burlap and strapping, before planting. After tree has been positioned (top of root ball should be even with original soil grade), fill hole halfway - with saved soil, cut strapping, roll down burlap and complete filling hole. A plastic covered root ball is handled in the same manner, except that before planting, slits should be cut in the plastic's bottom half - this facilitates water drainage and root penetration. Water thoroughly and mulch.

https://teachbesttech.org/the-modern-christmas-tree/