Watering the Christmas tree depends on the tree species, environment, and tree size. For most trees, 20 to 30 days is a good estimate to ensure the tree stays hydrated and healthy. However, certain types like Norway Spruce or Fir may need more frequent watering, while others like Cedar or Redwood can go longer between waterings. Check the soil moisture level regularly with a finger or moisture meter, and water when it's dry to the touch, usually every few days or a week.