This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The planter of Pears has the choice of two stocks upon which they may be budded or grafted, namely, the Pear and the Quince. On the former the many fine specimens of Pear trees seen in old gardens have been grafted. Some of them are of great age, with trunks like forest trees, and still carrying heavy crops of fruit.
The characteristics of trees on the Pear stock are vigour of growth, deep rooting, and slowness of coming into bearing (although to this last there are exceptions). On the Quince stock the tree grows slowly, makes fruit spurs quickly, and bears finer fruit, as the root tendency is to form a mass of fibrous rootlets near to the surface. Pears on the Quince are able to adapt themselves to a slightly wider range of soils than on the Pear. In planting, the tree on the Quince should have the place where scion and stock unite put 2 in. or so beneath the level of the soil; on the Pear stock the tree must not be put in so deep. The difference of stock sometimes gives rise to a wide divergence in the appearance of the fruit. If specimens of "Durondeau" and "Clapp's Favourite " from trees on the Pear and the Quince stock are placed side by side, it will be sometimes difficult to recognize that the fruit from the different stocks are of the same variety.
When on the Pear stock the wood should be shortened back each winter to about one-third the previous summer's growth, always making the cut just above an outside bud. Care must be taken not to leave more shoots than will be necessary to form the main limbs of the tree. Some varieties, like the "Hessle " and "Emile d'Heyst", will fall into line readily; others, like the Jargonelle, will persistently choose the wrong road, and require careful training. After the fourth or fifth year it will only be necessary to take out the "sprew" or spray wood that will come each season along the branches, and to thin out where the growth of wood is likely to produce entanglement.
On the Quince, most Pears lend themselves easily to training in the pyramid shape (fig. 352), although some varieties, like " Conference ", take more readily to the bush form. It really does not matter in a market plantation, and the wisest course is the line of least resistance.
It does not pay to plant the common varieties of Pears, that come to the cheap barrow trade, on the Quince. This stock is only suitable for such as will produce table fruit that will realize a decent price; then the tree will pay for summer pruning. This consists in shortening all the latest growths except leaders, during the latter end of July or beginning of August, to one-third of their length; afterwards, in winter, spurring them back to two or three eyes. Pears that are worth planting on the Quince will pay for thinning in the spring after the fruit has set, and has escaped the attentions of the Pear Midge. All varieties of Pears are liable to over-bloom themselves and waste the energy that should go to producing fruit in making of themselves a spring glory. When on the Quince this tendency can be checked somewhat by taking off superfluous bloom spurs before they open in the spring. In the case of full-grown trees on the Pear stock this would mean so large a contract that most growers will prefer to leave this matter to nature.