This section is from the book "The Gardener V2", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
Perhaps the subject upon which I am about to treat would have been better discussed at an earlier date; but its importance to juniors in the horticultural profession, as well as to others who look for counsel and advice from the columns of the horticultural press, may in all probability render it a welcome subject even at this advanced period of the season.
Many people engaged in horticultural pursuits have but a vague idea of the object of pinching and summer pruning generally. For what purpose do we pinch? and how shall we illustrate the practice? Pinching is performed for two or more purposes. One is to cause a plant consisting of one or more shoots to develop into, say, a bush of twenty or thirty shoots; the second - and not the least important - is to concentrate the growth and vigour of a plant into one or more stems or shoots, in order thereby to produce a greater degree of perfection in the size and shape of the flowers. Let me give a simple practical illustration : I will take the Chrysanthemum as the most suitable subject. We will suppose a plant having three shoots : these shoots are pinched, and presently the plant develops nine shoots, and so on ad libitum, until the little plant of three shoots has grown into a specimen of three feet.
It was asserted early in the present year by a cultivator that the finest Chrysanthemum blooms are invariably produced upon the "terminal bud;" and this expression of opinion was endorsed by the editor of a contemporary, whose eulogy of flowers produced upon lateral growths created not a little consternation in Chrysanthemum circles,and brought the writer of this article at least half-a-dozen letters inquiring if I knew exactly what ballast such authorities could safely carry without foundering. " Flowers produced upon laterals being as handsome as could be desired!" As well might we compare a bunch of Grapes produced from a lateral, with one borne upon the leader of a Grape-Vine. But I have undertaken the task of elucidating the practice of pinching, and the time at which the operation should be performed. You pinch a plant, and you then watch the effect produced by the operation. The cultivator who pinches at random says: pinch as often as you like up to a certain date, and the result will be the extension of the plant, and a proportionate increase in the quantity of flowers. It is true the plant will increase in size, and the flowers in number, but what of quality? The finest flowers, says a learned authority, are produced upon the terminal bud.
Now it would be wisdom on the part of those who think so to remain silent for at least five years upon this subject, and meanwhile to apply themselves more strictly and observantly to the practical details of superior cultivation, and after that time I venture to think they will have altered their opinions, much to their own advantage and that of others. As a matter of fact, the best flowers are "not produced upon the terminal bud," and such random conjecture is very misleading, if not mischievous to many.
But some one may say, Where is your proof? Anticipating a challenge upon the point, I will again revert to the plant having three shoots, each of which is pinched, and which in a short time produces three shoots each, or nine shoots in all. If these shoots are not further stopped, a bud will form itself upon the point of each shoot during the month of July. No notice should be taken of this bud, and in a short time three more shoots will radiate from the base of this bud, two of which should be removed by pressing them in a slanting direction with the forefinger of the right hand, or what is better, by using a small wooden peg, something of the size and form of a lead pencil, made soft at the point by squeezing it between the teeth. By this simple process the vigour that would naturally be equally divided into three shoots is retained in one, and the flower produced upon such a shoot will be perfect in form (globe-like), having fine broad petals, rich in colour, and of fine substance. The plant grows on with increased vigour until the early part of the month of August, when another bud will appear upon the point of each shoot, and these are the buds that produce the fine flowers - not the "terminal buds" of the writer before referred to, whose flowers were so handsome last winter, and who had a crop of lateral flowers into the bargain !
A common error with cultivators is to pinch back into the hard wood, instead of merely "rubbing off the point of the shoot," which is the proper way to do in all cases of pinching. Again, in the case of Vines or other fruit-trees, pinching is a very important operation. Let us look at the result pinching produces upon the Vine. Plant two Vines, and grow both upon the single-rod system until the canes have reached the length of from 9 to 12 feet; then stop one and let the other grow on, and note the result. No. 2 extends in length, while No. 1 increases in thickness; in other words, the result of pinching in this case is to localise or concentrate vigour. I suppose it is hardly necessary to remark that, when a Vine is pinched the extremity of the shoot only should be removed, and the lateral growth should be pinched out from the side of the first bud next to where the Vine has been stopped. In the case of Peach-trees, pinching should be done when the shoot has grown 2 or 3 inches in length. A shoot may be pinched because it is too strong, or because additional shoots are required to fill up vacant spaces in the tree; but in any case the operation must be performed shortly after the tree has started into growth, or the result will be immature wood and scanty crops.
I have seen Peach-trees converted from their natural habit of growth into myriads of fruiting spurs, by judicious pinching and restriction at the root, until in the winter many people mistook them for Plum-trees. Pinching enables the cultivator to turn a plant or fruit-tree into any form or shape, if he only knows how and when to do it. You do not achieve results by pinching because Dick, Tom, or Harry did the same, at the same time the year before, but because you are capable of judging, from the condition of the plant or tree before you, that the operation will produce beneficial results.