Concord grapes are not the kind of seedless grape that you buy in the grocery store for eating. Concord grapes are very "seedy" and therefore are used solely for jams, jellies, juice and wine (although a friend once made a concord grape pie - very different).
Harvesting concord grapes is very easy - find a ripe cluster of grapes and simply snap the stem off of the vine. The color should be dark bluey purple or (depending on the variety) a burgundy purplish red (I grow both of these varieties)
On October 1st (2011) I will share with you my super easy, delicious and nutritious grape juice recipe - "stay tuned!"