Traditionally, people add a special Christmas tree preservative to the water in the tree stand. This helps to keep the tree hydrated and healthy, preventing it from drying out too quickly. The preservative usually consists of a mixture of water and additives, such as sugar, glycerin, or preservatives. The sugar acts as a food source for the tree, helping it stay vibrant and green, while the preservatives prevent the water from becoming stagnant or bacteria-ridden.