Well, since Christmas trees are typically planted outdoors, they're able to get their water from the soil. But if you're bringing a tree inside for the holidays, it's important to keep it hydrated by giving it plenty of water. Place the tree in a bucket or basin that's filled with water, and make sure the bottom of the trunk is submerged. Water the tree every few days, and keep an eye on the water level to make sure it doesn't dry out.