Answer: The standard recipe to help prolong the life of cut flowers is one tablespoon sugar and one teaspoon sugar to a gallon of water. The acid slows bacterial growth and the sugar provides nutrients, keeping the flowers alive longer. There's no reason why it wouldn't work for Christmas trees. The important thing is to keep the vascular system working by keeping water available at all times. (Without a constant supply of moisture the cut end will seal up and no water will circulate throughout the vascular system of the tree. This will result in premature drying of the needles.)
Hope this answers your question!
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