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.
125. This is a most important operation. It consists in the suppression of the herbaceous extremities of young shoots. These are taken off by pinching them between the nails of the thumb and fore finger. It is done with the view of diminishing the growth of those shoots which push too vigorously; while at the same time the sap that these would have have otherwise appropriated is turned to the advantage of the weaker shoots. Pinching differs from disbudding, inasmuch as it is only a temporary way of checking the excessive growth of a young shoot; while disbudding is its total extinction.
126. For this reason we pinch nearly all the young shoots, the growth of which we find it necessary to moderate, wherever they may be situated; and this is also frequently done with the view of assisting the development of other shoots. Thus we pinch the terminal shoot of a branch that has reached the desired length, in order to stop the sap, and turn it to the advantage of the lower shoots and eyes, a greater development of which is necessary to the end in view.
127. Pinching requires a great knowledge of the mode of vegetation of the Peach tree. It is indispensable for trees on walls, and it is more especially necessary for the upper parts where the sap flows most strongly. This operation is performed at no fixed period, but is done when the tree requires it. It must be several times repeated from the end of April till August, the particular periods being regulated by the state of vegetation in different trees, and by that of different parts of the same tree. When the balance of the tree is threatened, recourse must be had to pinching. It is well, therefore, to watch the progressive indications of the flow of sap; for in consequence of strong shoots resulting elsewhere from its check by the first pinching, the operation frequently becomes necessary on them. Those young shoots, which, by their appearance or position, promise to become very strong, should be pinched before they reach the same length as the others that are less favorablv situated, and not so well established. The former should be pinched when three or four inches long; the others must be left untouched till they attain the length of from twelve to sixteen inches.
In every case we must bear in mind the necessity of preventing the eyes that form on the young shoots, and especially those on their bases, from becoming blind, which might take place if the shoots were allowed to grow too long. We must also avoid, as much as possible, the pinching of them before they are of sufficient length, as it is likely to make them produce laterals. I usually pinch the young shoots behind a leaf, so that the tree does not appear to have undergone the operation; and many cultivators wonder at the regularity and well-balanced strength of its shoots.
128. Some laterals can not be prevented from forming on the young shoots that are retained, and particularly on those which have been pinched. The laterals which push on the leading shoots should, for the most part, be pinched when six to eight inches in length, above the second, or from that to the sixth leaf, according to their strength. On the leading shoots, pinching should be preferred to disbudding, which entirely destroys the origin of the lateral. Pinching, moreover, is favorable to its good organization, by encouraging the eyes that are formed along its base, and which fit it for becoming a fruit-branch on the prolonging shoot when the latter shall have become a wood-branch.
129. It is by no means uncommon for the terminal shoots of fruit-branches, situated on the upper sides of the principal branches, to grow to an extent likely to prove hurtful to the successional shoot. The former must then be pinched, but leaving it so long as not to make too much sap flow to the latter. If this pinching cause Borne of the eyes to burst into laterals, it must be discontinued, and the shoots must be cut down to the lowest lateral by a Bummer-pruning. If, in its turn, the young successional shoot acquire too much strength in consequence of these operations, we must endeavor to moderate it by pinching. If, occasionally, some of its eyes push laterals, it may be cut down, by summer-pruning, on a dormant eye; or, if none such exist, on its lowest lateral.
130. With respect to the laterals which break out prematurely on the young shoots, pinching is much more important for those situated on the upper side than for those on the lower. The latter, from having a less flow of sap, do not always require to undergo this operation.
131. Pinching being an operation entirely depending on foresight, it should be well considered; for when carried to too great an extent, its effects are disastrous: therefore I recommend great care to be taken in practising it; and I may say, that on my trees only a third, at most, of the young shoots undergo the operation.