In all climates grafting in the top is often an advantage. Usually the gain comes from working a highly developed variety of fruit, rather delicate and tender in tree, on robust, deeply rooted stocks nearer to Nature. Over Europe and a large part of Asia native wild stocks have been largely used, noted for their ability to endure every extreme of given climates. At the Pomo-logical Institute at Proskau in North Silesia the writer asked the venerable and experienced Dr. Stoll to name the most satisfactory stock for top-working in that section. His reply was that no one variety was suitable for the varied soils and altitudes of even that vicinity. He then proceeded to name the best stock for top-working on sandy soils, retentive clays, porous soils and subsoils, and even for lands naturally swampy and boggy. As yet we have not been able to make these fine distinctions in the adaptation of fruit varieties and stocks to varied soils and atmospheric conditions, but we are rapidly gaining ground in this desirable direction.
In the more favored parts of the Union top-grafting as yet has been confined mainly to changing the tops of seedlings and undesirable varieties. In the citrus-growing districts in like manner the work has been mainly confined to changing the tops of seedlings and unprofitable varieties. In the prairie States some progress has been made in selecting stocks noted for their hardiness and inherent vitality, such as the Virginia crab, Gros Pomier, Hibernal, and some of the robust Russian varieties. Some advance has also been made in following the European method of setting the stocks in orchard and top-working them the succeeding spring. This working of young trees permits the insertion of scions in the top and side branches, giving forks of the hardy variety used for working, as shown in Fig. 47. In top-working young trees it is best to use the side-cut method as in crown-grafting plum and cherry (8G). If the waxing is done with the liquid plastic covered by winding with white cotton strips, it answers the purpose of tying. Yet as growth goes on the covering loosens without injury to the graft or stock.
Fig. 47. — Top - grafting the apple.
In the South and the States east of the lakes top-working old trees and undesirable varieties is so common that travelling professional grafters follow the work each spring. In the prairie States this rough cutting-back was also tried by the travelling-grafters. But the dry and hot interior air developed ferment in the stock, blight, and other troubles that soon put a stop to the rough practice. At the present time the top is cut back less severely, or the grafting of one side at a time is practised. Even at the east experienced orchardists now graft more at the extremities, as shown in Fig. 48.
Fig. 48. - Old apple-tree top-grafted. (After Bailey.)
In grafting these larger limbs the scions are inserted by what is known as cleft-grafting, as shown in Fig. 49. With the tool shown at Fig. 50, the cleft is cut rather than split if the tool is made thin, smooth, and sharp. At the top of the tool is a wedge which is driven down in the centre of the cleft while the scions are being inserted. In making the wedge on the scions the cuts should be flat, so the pressure when the wedge is taken out will not crush the bark and cambium layer. In applying the wax (83. Grafting-wax for Varied Uses) it should be crowded into the cleft tightly before the wedge is taken out. In interior climates it is best to cover the wax with white cotton cloth to prevent its melting or cracking.
In top-grafting old seedlings or undesirable varieties of the pear the same plan is adopted. But in mild, relatively moist climates the plan adopted often with seedling orange-trees in California is to cut back one-half the top the first season and to permit vigorous sprouts to grow.
The next spring the other half is cut back and the sprouts of the preceding year on the other half are spring-budded (76. June Budding). The succeeding spring the other half of the tree is budded in the same way. This is really a profitable plan for all top-working of large trees.
Fig. 49. Fig. 50. Cleft-grafting the apple.