Many nurseries offer live, potted Christmas trees including: pinyon, ponderosa, limber, Austrian, bristlecone, and Scotch pines. Other varieties include: blue spruce, dwarf Alberta Spruce, white fir and Douglas fir.
These potted trees are usually sold when they are two to six feet tall. Before purchasing one, decide where the tree will be planted after Christmas. Consider the mature size of the tree, and the weight of the potted tree. Most nurseries will hold the tree until you want to take it home.
The two most important factors for successfully growing a live potted tree are 1) to not allow the rootball to dry out and 2) avoid keeping the tree indoors too long. Seven days indoors is a maximum time recommended, however five days is better. Many families have developed a tradition of bringing the tree indoors for decoration on Christmas Eve and planting it outdoors on New Year’s Day. It can be helpful to pre-dig the planting hole, as the ground may be frozen in late December and early January. Store the soil backfill in the garage or outdoors in a black plastic bag so it is less likely to freeze.
You can keep the potted tree in the garage for a few days before bringing it indoors, but frequently check the rootball to ensure that it stays moist but not soggy. After Christmas, the tree can again be placed in the garage for a few days before planting outdoors. While indoors, decorate the tree with small lights, which generate less heat, and place it away from sources of heat; like fireplaces, heat vents and television sets.
For more information, see the following Colorado State University Extension fact sheet(s).