I planted a Thompson and Concord grape from 15 gallon containers two months ago, and pruned off all the old growth except a main vine and a few spurs. (I pruned them differently according to their variety, though now I can't remember which one was spur pruned and which was cane pruned.). They are now growing nicely, however since the pruning heads were about 8 inches off the ground, from spending two or three years? at a nursery, the new growth is of course coming out of that low head. Since I want the new growth to come out of a head that is a good 3 feet off the ground, should I prune the whole vines below these previously formed heads in order for them to send a brand-new shoot up to the three-foot mark? In which case, is it now too late for this season, since the vines are growing strong, at about 2 feet tall or so, with a good handful of tiny clusters each, or can I still chop them down and watch them grow back even in this season?

I understand there would be bleeding – but I don't know what that means for the plant.