How long will a cut Christmas tree last in water?

When you get your tree home and before you bring it inside, cut at least 1 inch on a small slant off the bottom. This creates an open "wound" that the tree can take water through. As long as you keep the bottom of the tree and the entire cut area filled with water, you should get a good, solid month out of the tree before it starts to dry out and lose its needles.