I started my kids learning certain trees. At the same time I taught them which animals these trees were important too and why. Now I'm doing this with my grandchildren, just like my dad did with me. I have an advantage because of my chosen profession -- Purdue made me learn this stuff and more (Forestry and Wildlife). We had to learn about 120-130 trees and shrubs, field trip quizzes every class for a year.
I'll never forget my first job in Colorado. I had to know only 5 trees in that job. Diversity in the east is so much greater and challenging.
I can only imagine how much a hunter misses when they don't know various oaks, hickories, persimmon, dogwood, honeysuckle (even the pervasive exotic), etc. At least know the "pointy" end-lobed red oak from the round end-lobed white oaks so you'll know which will produce acorns every year and which will only produce every other year. Know that 3 burr oak acorn will keep a squirrel alive on a winter day while it takes 11-13 red oak or walnuts to do the same (it takes much more energy to get to the meat of a walnut).
My oldest grandson didn't seem super interested in learning this stuff, I think he just took it for granted because he was around it all the time. Then his dad (my son) received his bow-killed Kudu and Impalas from the taxidermist. Now he is a monster! He's bought two wildlife i.d. books (Africa) and is constantly downloading photos on our computers, phones, and his i-pad.
He also went on his first deer hunts this past season (not ready for bow yet). He is hooked!
Of course the comfort and survival skills Rob refers too are critical as well. Especially to give the hunter confidence that they are in safe and much control over what happens in the wild.
I'll be getting my oldest grandson a compass this year. We'll use it and an aerial photo of the farm we hunt to do some orienting. We'll also discuss hunting edges, and predicting from the aerial where good deer sign should be.
I have to be careful though in all this "teaching" too make it practical and fun, almost subliminal. Mom and dad are for teaching and discipline, Papaw and mamaw are for fun'n.