These are Concord grapes. I got this variety from a friends' backyard 30 years ago. This variety had been growing in his yard for 75 years. This year I harvested half of the grapes from each plant. They were averaging 15 brix. Within 3 days, the remaining half now averaged 19 brix. When God says to leave the fruit that you missed while picking, for the poor, the stranger and the beasts, He is giving them the best quality fruit. I observed a similar incident one winter in a Florida citrus grove. A freeze was coming. Half of the tangerines were picked from each tree, in part of the grove. The remaining fruits on these trees was not freeze damaged, because the brix level was increased in these fruits. In the section where no tangerines were picked off the trees, the fruit was freeze damaged.