One way to make a Christmas tree last longer is to ensure it is well-watered. Christmas trees are living, breathing plants that need water to survive. When a Christmas tree is properly watered, it will maintain its green color and freshness for much longer. To properly water your Christmas tree, fill the base of the tree stand with water and add a Christmas tree preservative to help the tree absorb the water more effectively. Also, keep the tree away from heat sources such as a fireplace or heater as this can cause the tree to dry out faster.