So, while Vinny was staying with his grandparents, my dad was walking with him through a parking lot, where Vinny proceeded to rattle off the make and model of every single car. If he could identify cars, Dad thought, then surely he could learn to identify trees too. So that week, Dad helped Vinny to create a leaf collection and learn all the leaves.
There are a couple dozen different leaves in that book, and Vinny knows them all. He can flip through the book and rattle them all off, but also he can identify them out of order or even outside of the book. He took the leaf collection book to school and showed it during show and tell. His teacher was amazed by his leaf knowledge, and so am I. I think that at this point, he can identify more leaves than I can. The mind of a four-year-old is like a sponge!