Cut Christmas trees can live anywhere from four to six weeks indoors when placed in a stand with a well supplied water bucket or reservoir. Although some of its longevity will depend on the species of tree that you buy and its health when you buy it, there are things you can do to help it to live longer. Make sure that the trunk is freshly cut so that it can easily take in water. Always make sure that it has plenty of water, and keep it way from sources of both heat and cold, which can cause the needles to fall off.
Choosing a Species
Some species of Christmas tree last longer than others. For instance, an Eastern red cedar dries out quickly and lives only two to three weeks after it is cut, whereas Balsam or Fraser firs tend to hold onto their needles and can live up to six weeks. Blue or white spruce trees also hold onto their needles longer. People who are worried about not being able to water the tree daily may wish to get a Scotch pine or a white pine, as they have needles that will stay on even when dry.
Cutting the Trunk
After purchasing a Christmas tree, you or the salesperson should cut a straight disc off about 0.25 to 1 in (0.635 to 2.5 cm) from the end. Within six to eight hours of being cut, submerge the trunk in water. When a tree is cut, it produces sap to cover the wound, but this also prevents it from taking in more water, causing it to die much more quickly. If yours was originally cut down fewer than 12 hours before, you don't need to recut the base.
Storage and Placement
It's best to cover your Christmas tree before placing it on top of a car to protect it on the drive home. You can store it outside for a few days before setting it up, as long as it's in a sheltered area. It's best to place the tree in a bucket of warm water if it's going to be stored for more than a few hours.
When it comes time to place the tree in a stand, some people cut or trim off sides of the trunk to make it fit. This may make it sit more securely in the stand, but also causes it to die quicker, as the outer layers of the trunk take up the most water and without them, the Christmas tree dries out and dies. By measuring the trunk diameter and purchasing a stand that can hold it, you can preserve the outer areas and make your tree last longer.
Water
Cut trees can use up to 1 gallon (3.8 liters) of water within the first 24 hours of being in the home. Some water reservoirs may appear to have enough water in them, but the water level may not be high enough for the trunk to access it. Check the water level daily to make sure it doesn't drop below the end of the trunk. Plain tap water is generally all that a tree needs to stay alive through the holidays. Though some people like to use commercial powdered Christmas tree food, aspirin, sugar, or other water additives, as they believe that it helps it last longer, although most experts say that these do not actually help.
Temperature and Humidity
Another way to lengthen the life of a Christmas tree is to set it in an area of the home that isn't near cold air drafts or heat sources, since these can cause the needles to turn brown and fall off. Cold air drafts may trigger needle drop, which is a natural response that evergreens have when they prepare for winter. Heat from fireplaces, candles, and some types of Christmas lights can be drying as well, and may cause needle loss. Using a humidifier can also keep the needles from drying out.
Safety
Dry Christmas trees can be fire hazards. Their branches and dead needles can easily catch fire when standing near the open flames of candles and fireplaces. You shouldn't use lights with worn or frayed cords, as they can spark when turned on and can start fires.
Using lights that emit low heat, such as Light-Emitting Diode (LED) lights, may reduce the amount of drying that the needles will undergo. Turning off all lights before leaving the house or going to bed can also help keep the branches cool and prevent them from drying out.