I have a volunteer grape vine that grew up in a garden bed off to one side of the patio. So it could have been people spitting seeds from one end, or it could have been birds contributing from the other end that started it.
This year, the vine bloomed and produced some sparse fruit clusters. I haven't taken care of the vine except to keep it pruned to reasonable size. I haven't fertilized and it grows with rampant peppermints and Japanes parsley, so it's safe to say it is undernourished.
Is there any way to tell at this stage if they look like wild grapes?