Some people mistakenly refer to rhubarb as fruit, because, with the addition of sugar, we get a somewhat sweet (sweet/sour) sauce, pie, or whatever. It's not a fruit, because it has nothing to do with seeding.

So it's a vegetable? you say. No, not a vegetable either.

It's a leaf petiole.

Stick with me, kid; you'll learn all sorts of things you never wanted to know.

Dave Oesterreich