I think the answer is what cosmicvagabond said, without the corpse, and most of the poem is just filler to throw you off course.
Yeah I agree. That seems to be the best answer so far. I'll refer to the actual proposed solution as "A1," so as to avoid giving away the...scent.
I am confused by the structure of the riddle. It reads at turns like one of those where you have to figure out who "I" is, but clearly the narrator is asking us to figure out what this other thing is.
We know stuff about "I," but maybe it's superfluous stuff?
Because I do not hope to know
This mystery at this late hour
Because I do not think
So is this stanza just a throwaway? At least in terms of the info necessary to solve the riddle? Is it just saying, "I'm tired, so this is perplexing to me?" I dunno.
Because I shall not know
Once thought to fuel this power
Was alcohol, which I cannot drink
Again, what is the relevance of the "I" and its lack of knowledge?
But OK, the rest is seemingly straightforward: This mysterious power was once thought to be "fueled" by alcohol. I'm not an authority on the history of human understanding of A1, and a minute or so of Googling didn't enlighten me further, but it sounds reasonable, the idea that people thought alcohol causes A1. And trees and flowers are where alcohol comes from, so to speak.
As to Evan's temperance, that sounds personal.
Because I can not know
Why it doesnt happen to tree or flower
Perhaps this bad habit is the link
But see, the narrator could know (*should* know) why A1 "doesn't happen to tree or flower." Which makes me wonder if the identity of the narrator is somehow part of the riddle.
Because I refuse to know
My impulsive human reaction seem dour
And whatever bits remain, boy, it sure does stink
The narrator doesn't appreciate the finer points of A1, so his low opinion of it isn't really fair? Humans do have consisently impulsive and negative reactions to A1. Despite the fact that it is a critical...well, you know.
"Whatever bits reman?" Oh man, that's gross. lol
I dunno. Now I'm hung up on A1, but it's probably something completely different.