I’m looking for a career change from i.t. to growing trees and plants. Rather than heading back to school I love learning so plan to learn from books and the internet. Any suggestions on the path I should take?
I suggest, as a very first step, that you take a local Master Gardeners course. It will hopefully open many doors for you.
The less you know about an endeavor, the simpler and easier it looks. Get a job in the specific business you're interested in and get your education in the School of Hard Knocks. One of two things may happen: you will see more just plain work that makes the field less satisfying, or you'll say to yourself, "I can do this better / serve the customers with a product or service being ignored." That line of thinking is the mother of invention.