Continuum fallacy. Whether or not something is a potato is ambiguous. When does something stop being the root of the potato plant and become a potato? As others have mentioned, what about french fries or potato chips? They are both potato and not-potato. This is a problem with two-valued logic (instead of continuous-valued logics, such as fuzzy logic) in that it requires a precise predicate to render a valid conclusion. See 'Heap Paradox' on wikipedia.
The word potato may have multiple meanings. A type of root is the most common, but calling something or someone a potato can mean a certain appearance or intellect. This renders that target as concurrently both potato and not potato.
How about a fraction of a potato? If I cut a potato in half, it does not constitute a whole potato and therefore not **a** potato (but rather part of one), but, at the same time, is still made of potato, and is therefore potato. Therefore, it is not black and white.
Assuming the universe is infinite, there are infinite possibilities of "things" existing. Therefore, there is "something" within the universe that is simultaneously a potato and not a potato. "Schrodinger's potato" if you will.