I enjoy the theory [idk if it was proven in the movie but I have to rewatch it] that Simon at least spent some years on Mars as a child. Probably doesn’t remember a lot of it, probably didn’t even look like the American west/southwest if humans colonized it or anything but I was reminded how much some of our landscape resembles Mars.

This, but also even if you don’t think he lived on Mars for a bit, I would imagine actually any trees at least at the beginning, for him, is a little… too much. Even if they’re green and vibrant. Watching the movie a few times made me realize that their trees are not like our trees and if indeed he may have a hand in feeding bodies to the tree then trees in general are not what he’d like to be around. Plus they block the sky.

It occurred to me that poor dude has like… never seen the sun. Or a big ol blue sky.