Concord Grapes http://www.durgan.org/URL/?YLZVT 16 September 2009 Concord Grapes. This is the only grape vine out of four varieties that produced reasonably well this year. The clusters should be fully ripe in about two weeks. Concord is probably my favorite table grape, and if I have extra juice is made. It requires a lot of grapes to get any reasonable quantity of juice about 8 pounds per liter- but wonderful juice. This is the four year for this plant.