Technically speaking, the Elder Scrolls world is a completely different one from our own, it just happens to look a lot like ours in many places. And even if the fundamental workings differ greatly from our own, many things, on the surface, seem to behave much as we'd expect them on Earth (except where magic is involved, of course.). So while there may be many plants that are based on real life plants, it seems reasonable that they might differ in some ways, whether in appearance, or in other properties. In fact, I'd say it's sort of necessary for the game for them to differ in some ways, since I don't think there are any plants in real life that induce spontaneous combustion when consumed.
I guess it's like how rats are bigger than the ones you'll likely see in real life, and much more aggressive.