While clearing brush, sucker black locust trees and weeds for a garden area this spring I discovered an old grape vine. The neighbors say it is a concord, somewhere around 50/60 years old and had the best tasting grapes. So instead of yanking it out I strung the vines out along a chain link fence. Now I have 50 feet of grape vine growing wild and crazy and what looks to be a bumper crop of grapes. The trunk is old and gnarled and instead of going staight up runs along the ground for a couple of feet, bends back over itself for a couple of feet and then heads west for a couple of more feet before splitting into the three huge vines that I strung over the fence. Can I, should I try to prune this back to normal garden sized grapevine and if so, how and when. If not, can I propagate it somehow? Thanks.