If you choose and prepare your Christmas tree carefully it should last at least two weeks indoors and often much longer depending upon the kind of tree you purchase, the conditions in your home and the care you give it.
There are several kinds of trees commonly used as Christmas trees. By nature, some hold their needles longer than others. As a group, pines hold their needles the longest. They can be recognized by their longer needles, 3-5 inches, that are attached to the branches in clusters of 2-5 needles. Common pines used for Christmas trees are: Scots or scotch pines, white pine and red pine also called Norway pine.
Next in line are the true firs, these include balsam fir and Fraser fir. They both give off a wonderful fragrance. Balsam fir will not hold its needles as long as Fraser fir but Fraser fir is more expensive. Next is Douglas fir which is not a true fir. It looks somewhat like spruce but has soft needles. Spruces can also be found but the sharp, stiff needles and their tendency to drop needles quickly reduce their desirability.
After purchasing a tree it's up to you to keep it fresh. Transport the tree to your home with care. Trees exposed to wind during the drive home can dry out. If the tree will be exposed to wind, wrap it securely in a blanket or plastic tarp to protect it.
After arriving home, make a clean cut on the base of the trunk. Remove at least 1 inch of the old trunk. This exposes fresh tissue which will absorb water more readily. After cutting, even if the tree will be stored before setting up inside, place the cut end into water. Once the tree is indoors, check daily and keep the water level at least one inch above the base of the trunk at all times. Do not let the stand dry out.
Fact Sheet: Selection and Care of Christmas Trees (PDF)
Plant Finder profiles for common Christmas tree species
Balsam fir (Abies balsamea)
Colorado spruce (Picea pungens)
Douglas fir (Pseudotsuga menziesii)
Eastern white pine (Pinus strobus)
Fraser fir (Abies fraseri)
Scotch pine (Pinus sylvestris)
White spruce (Picea glauca)