"How shall we prune" is a question probably more frequently asked than any other in the whole range of horticulture. To answer it brings forth a second question, viz., "Why do we prune?" Pruning is a means to an end. So then to prune intelligently and therefore successfully, there should be in the mind of the operator some definite purpose. Too often pruning is simply a cutting of the tree without any idea as to the final purpose such cutting is to serve. Such pruning invariably does harm instead of good, and has ruined countless trees. Since the ultimate purpose of a shade tree is different from that of a fruit tree it is evident that it should receive different treatment. A tree grown for wood or timber should be managed still differently from either. Again, a fruit tree bearing on one-year-old wood must not be pruned the same as that bearing on two-year-old wood. Upright-growing varieties require to be trained on a different plan from those of spreading or drooping habit. The nature of the pruning any tree should receive will depend, therefore, on the purpose for which the tree is grown, on its variety, and also on its habit of growth. In short, to prune intelligently we must understand trees.
Hutt, W. N., "Bulletin No. 83 - Pruning of Tree and Bush Fruits" (1903). UAES Bulletins. Paper 34.