'Edible' in the Bible

He built a hedge around it, removed its stones, and planted a vine. He built a tower in the middle of it, and constructed a winepress. He waited for it to produce edible grapes, but it produced sour ones instead.

What more can I do for my vineyard beyond what I have already done? When I waited for it to produce edible grapes, why did it produce sour ones instead?