The X-mass tree is also called the Christmas X-mass tree. A wellhead control device for oil and gas testing after oil (gas) well completion, or for oil recovery from wells and machine wells. It consists of a tubing hang and many gates and tees or crosses that are mounted directly on the casing head. Christmas Tree oil and gas. The Christmas tree is a piece of equipment that provides flow control on a producing oil or gas wellChristmas tree (oil and gas). A vertical assembly of mechanical elements used in oil exploration and production in surface and underwater oil and gas wellsOil and gas production.