The amount of water a Christmas tree needs depends on the type of tree and how long it has been cut. For fresh-cut trees, they should be watered daily. This will help the tree stay fresh and healthy. If you are using an artificial tree, then you don't need to water it at all. However, if the tree is made from natural materials, then it may need to be watered once or twice a week. Just make sure to check the moisture level of the tree and adjust your watering routine accordingly.