So, I just replayed Grim Fandango (solid game by the way) and I just came to this realization about the sproutella gun after seventeen years.
When shot by a sproutella gun, your body is flooded with seeds and chemicals that make you erupt into flowers, destroying you in the process. The reason that this unusual method of "killing" was chosen is because bonemeal is a very potent fertilizer.
Genuine oldfaggery detected; Abandon post!
I never understood the sproutella gun but I guess that makes sense. I thought the game actually kinda sucked when I replayed it because all the puzzles are spelled out for you or end up being trial and error. The art and writing are mostly good though, and definitely hold up against the garbage telltail puts out.