This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
The summer pruning of grapevines commences with the first inch of growth, and if then performed, and carefully continued during the entire season, we should hear nothing of the injury attendant on its practice, nor could we find an opponent thereto. It is by rubbing away at once all buds, which, if left, would grow to useless wood - it is by carefully just nipping the end of a shoot and directing its energies into more rapid and perfect development of the wood and leaves already formed, that we can summer prune, guiding the supply of food to the sources we desire expanded; and yet our most strenuous opponent can find no point of attack; for in this course we have never robbed the vine of any amount of expended food, or by the destruction of a single leaf or twig sent a vibrating thrill of disease toward the root.
It is already time to be about the work, and in many sections perhaps long past the time, for the seasons of our Southern Mends are much earlier than ours.
According to the mode of training and winter pruning, seek now to guide the sap -and growth into canes for next year's*fruit-ing, and also into strong and healthy leaves on those already setting with fruit, carefully and severely rubbing out all buds or young shoots that tend to crowd the vine with foliage and at the same time extract supply from the roots. The simplest, and we believe the best method, is that of renewal canes from the ground yearly; and the vine should be now carefully studied, to judge of its capacity to fruit another season on two, three, or more canes, and such should be left and carefully guarded - not even a lateral touched during the season - but all others should be rubbed out and kept out.