Hello. The house that we moved into a few years ago has 4 grape vines growing in the backyard on a trellis. Since I am brand new to winemaking I haven't done anything with these vines since I have been here but am looking to see if I can make these vines productive. They do produce grapes (Concord I think) but the clusters are small with some ripening very early and others late. I don't know how old they are but the vines at ground level are about 3-4 inches thick. From there they grow up into a big tangled mess about 12 feet high. My question is, can I prune these back to a few feet from the ground and then train them along the trellises without killing the vines? I would like to be able to get enough grapes from these to be able to make a batch of wine each year. If I do prune them back do I need to leave some leaves? There are very few leaves near the bottom of the vines. Would it be better to just rip them out and plant new vines? Is anyone aware of a good source of info for reclaiming old vines? Thanks.