We had heard that putting a little sugar in with the water of the Christmas tree stand would help keep the tree green and the needles from falling off. However, after about two weeks the mixture fermented (or had some other nasty microbial reaction). They could smell our tree all the way up at the North Pole. We wouldn’t have made this mistake thirteen years ago if Mythbusters had been on television back in those days.
Last season Mythbusters investigated all of the various home-remedies for keeping your Christmas tree fresh and green. The tree lost the fewest needles when Viagra or bleach was added to the water. But both of those additives also turned the tree yellow and ugly. Fertilizer, lemon-lime soda, and pain reliever had even worse results. Spraying the tree with hairspray kept the needles on the tree but was a serious fire hazard. It seems that the best way to keep your tree fresh and green is to just make sure that it has plenty of fresh water.
Or, you could just buy an artificial tree.