The term 'WHAT IT TAKES DECADES TO GROW' can be summarized as referring to something that takes a long time to develop, and the crossword solution for this is 'OLD', which is a three letter word. This term is often used to refer to something that has been around for a long time, such as a tradition or a skill that has been passed down through generations. It can also refer to something that has been around for a long time, such as a tree or a building.