I agree, the native hornwort doesn't seem to drop leaves nearly as much as what you find in aquarium shops. I guess I didn't really think about it until now, but back when I had the tropical kind, cleaning up the shed leaves was an absolute chore and they always were floating around everywhere and stuck to the filter... Now, the native stuff hardly ever loses ones unless I accidentally snap them by grabbing them too hard or something.
Something even stranger I noticed: the bottom parts poked into the gravel didn't wilt and rot into a nasty mush like the tropical kind did, rather, the leaves sort of blanched white but remained crisp and firm, and helped anchor the plant in the substrate. I'll have to get a pic sometime, I thought it was bizarre...
Besides that, the native one has flowered and gone to seed for me. Finally, it gets a richer rust-orange tint and pink stems when it grows close to the light. Very pretty.
Aaaanyways, make sure you check Wisconsin laws on plant collection and get permission to collect from private lands before you do and whatnot.