On my plot, I have pergolas 3m high on which girl’s grapes grow, it is beautiful and creates a shadow on my sunny plot, but over time there were difficulties with pruning the grapes, and it is especially difficult to prune it so as to maintain the shape of the arches. Maybe someone knows how to do this without resorting to additional devices. My husband and I set tall ladders with which he cuts the grapes, and while I am on the ground I tell him where to cut, so that the shape is beautiful. Here is a photograph of the arches, but here the grapes were still young, and this year it was very overgrown, although we cut it well in the fall.
The whole secret to pruning grapes correctly is to prune an older vine relative to other vines (young). But then inevitably observed, as the author of the question correctly noted, the loss of form. In order to preserve the shape of the arch and at the same time give the grapes further growth, it is necessary to observe several rules: it is best to start cutting the grapes in spring and closer to the beginning of summer - this is when its active growth is observed. Secondly, the procedure for pruning vines (I note the old vines) should be carried out regularly. And thirdly, if you really don’t really have to resort to additional means to preserve the shape of the arch, you still have to sacrifice the quality of the plant itself, that is, its potential ability to constantly develop and grow - therefore, young grapevines will also have to be cut to the detriment of the quality of the plant.
Thus, we either partially sacrifice the quality of the plant, but maintain a more or less arch shape, or we lose aesthetics, but we have a healthy, constantly growing grape.
Sincerely, Igor Nikolaev.