Thinking ahead is key for transitioning a potted tree from indoors to outdoors during the winter. Before the ground freezes, choose a planting site, dig a hole and cover the opening to ensure no one falls in and it doesn’t fill with snow (or anything else). When Christmas is in the rearview mirror, place the tree in an unheated garage, on a covered porch or in a well-sheltered outdoor area, allowing it to acclimate to the cold without getting damaged or killed by the temperature shock. After a week or so, place it in the hole, still in its pot. In the spring, when the ground thaws, remove the tree from the pot, cover its roots in a mixture of dirt and compost, add a light layer of mulch and water it.

Source link: https://www.washingtonpost.com/home/2023/11/21/potted-trees-christmas-tree-alternative/