Christmas trees come in all different shapes and sizes, and they vary in age as well. Some are quite young and have only been growing for a few years, while others are much older and have been growing for decades. The age of a Christmas tree is typically measured in terms of how many growing seasons it has experienced. A tree that is 10 years old has been growing for 10 growing seasons, while a tree that is 20 years old has been growing for 20 growing seasons.