Verse Dt32-32 criticizing the behavior of the Jewish people states For their vine is of Sedomite vintage, from the fields of Gomorrah; their grapes are a poor man's grapes [bitter], [only] bitter clusters belong to them. Rashi's contribution is included in the translation of the text. Rashi explains that the Biblical phrase poor man's grapes refers to a particular grape species that is known for its bitterness. In fact since the grapes are bitter, therefore they are cheap and consequently are freqeuent at the tables of poor people.

A follow up on Rashi would be to identify the particular grape species involved. We have explained that explanations of the text that come from external sources - such as algebraic, diagrammatic, logical, or real-world facts including the biological, botanical and psychological sciences - are classified as application of the non-verse method. It is important to realize that such methods are bona fide Biblical methods that equally enrich our knowledge of Biblical texts. I unfortunately do not know the particular species involved. If I did I would know more about its bitterness and this would help me understand and explain the Biblical text.