A Christmas tree should be watered regularly, but the frequency depends on several factors such as the size of the tree, the type of soil, and the temperature and humidity of the environment. In general, it is recommended to water a Christmas tree every few days. You can tell if your Christmas tree needs water by checking the soil. If it feels dry and crumbly, it's time to water. Just make sure to use a water-absorbent mat underneath the tree to catch any excess water. Happy decorating!