1
general::
Fail to come to fruition, as in This building project will wither on the vine if they don't agree on a price. This expression alludes to grapes shriveling and drying up because they were not picked when ripe.
American Heritage Idioms
2
general::
Phrase(s): wither on the vine [and] die on the vine
1. Lit. [for fruit] to shrivel on the vine or stem, unharvested. • If we don’t get out there into the field, the grapes will wither on the vine. • The apples will die on the vine if not picked soon. 2. Fig. [for someone or something] to be ignored or neglected and thereby be wasted. • I hope I get a part in the play. I don’t want to just die on the vine. • Fred thinks he is withering on the vine because no one has chosen him.
McGrawhill's American Idioms And Phrasal Verbs