Yeah I know what you mean! I feel like it’s mostly experience based.

Woolly croton – I’ll check it out when I’m near the book. I’ve only got the first volume, I believe there are 4. There are also some recordings of lectures that he’s given. I wrote up a translation of a section in which he specifies a certain soil condition, and then lists all the plants that he associates with it. I think the whole thing is really useful as a rough map to guide your observations.