The Goophered Grapevine' was a story published in the book The Conjure Woman by Charles Chesnutt in 1899. It is nominally about a character named Uncle Julius. He tells the story of Henry, a man who would gain and lose strength based on the seasons, due to an accidental eating of some magical grapes.
The slaves, fearful of the goopher, avoid eating the grapes. Soon, though, their fears are confirmed when a visitor's coachman, unaware of the curse, eats some grapes and is killed that same night...