One tree will take 20 years to grow, acquire its own fauna, become a full-fledged forest. And other trees need 100-200 years for the same. On average, trees grow from 0.5 to 2 meters per year. Dwarf forms grow 15-20 cm per year. Trees gain their mass even more slowly. If you're wondering how to estimate the age of a tree, follow along How to tell age of a tree: tips you had no idea about.