Water is still the best preservative for holiday trees.
Make sure trees have a one-inch fresh cut. If the tree absorbs all the water, the basin is empty and you haven't noticed, a fresh cut needs to be made on the tree, even if that means taking all the decorations off. Aspirins, copper pennies, uncolas, sugar and bleach have not been shown to prolong the life of a tree. The higher the moisture content the less likely it is to dry out and become a fire hazard. Check for freshness by examining the needles.