Many people believe that adding vodka when watering a Christmas tree will help preserve the tree. The basis for this belief is the fact that alcohol thins various types of lacquers. Because many lacquers contain tree resins, adding alcohol when watering Christmas trees should, in theory, prevent the sap in the tree from skinning over where the tree was cut. This skinning over of the cut of the tree slows water absorption and causes the tree to dry out faster, so avoiding this skinning with vodka should prolong tree life.
While alcohol may thin lacquers and tree resins, it also tends to dry things out. Adding vodka and other forms of alcohol to Christmas tree water has, in fact, been shown to turn the tree's needles brown and cause the tree to dry out faster than water alone. Adding vodka when watering a Christmas tree is not only bad for the tree but also potentially dangerous to small children and pets who may drink from the tree stand.
What Does Work?
Home remedies and suggestions for preserving Christmas tree life are as varied as the people who share them. These remedies include vodka, 7-Up, crushed aspirin and more. Many of the chemicals specifically designed to preserve Christmas trees and cut plants do work. Others do not. The advice of the National Christmas Tree Association is to pick a fresh tree and keep it well watered with tap water.