i got you, in the underground tunnel system, in the last room ypu get access to look to the top left of the room and you'll see a leaf you can pull (note: unlike EVERY other version of this, the leaf isn't a different color) simply pull it to reach the golden tree.
I'll say, especially in the sewers, I strait up couldn't find the hidden rooms up in the top left corner until I happened to get a battle in both rooms, which I had to intentionally do after noesbecc told me the location.
