In apple production, some new varieties are often selected or introduced from abroad and other provinces. In order to speed up the propagation and understand the adaptability and growth of new varieties to the local environment as soon as possible, grafting and head-changing methods are often used for breeding. Top grafting is a method of observing and breeding by grafting branches and buds of introduced varieties on mature or young trees. Before grafting, the annual or biennial branches of the original variety should be cut off and grafted with the introduced variety. For highly grafted apple trees, the branches should be used for modeling according to the original foundation of the tree body, and there is no need to force the tree shape. For trees with all heads changed at one time, more branches can be grafted at first, but with the growth of branches and the gradual expansion of crown of new varieties, the number of high grafting will gradually decrease. When adult trees are grafted at high altitude, the number of high grafting can reach 300 ~ 400, and it should be kept at 40 ~ 50 after 4 ~ 5 years, and the number of high grafting is about 10 year. High grafting is easy to spread viral diseases. Therefore, the selected mother tree cannot carry the virus, and the grafting tools must be strictly disinfected to prevent the virus from spreading, especially the decline of apples.

It has been widely used for a long time to cultivate new varieties by high grafting, but with the development of science and technology, the new tissue culture technology has been popularized and applied in production because of its slow speed, small quantity and easy spread of virus diseases.

In order to promote early flowering and early fruiting of grafted trees, in addition to strengthening comprehensive management and pest control, summer pruning should also be coordinated, such as pinching, twisting, pruning, girdling or spraying regulators. The suitable girdling time of high grafting trees is in the middle and late June. The girth of girdling branches should be more than 30 mm, and the girdling width is about110 of the branch thickness, which can heal in that year. The branches are too thin, the accumulation is insufficient, and the effect of promoting flowers is not obvious. If the girdling is too wide, it is not easy to heal, which may lead to the death of branches in severe cases. In order to promote the growth of branches, when the new shoots grow to about 15 cm, they can be cored; In order to alleviate the growth of erect branches, pruning can be carried out in the growing season to make them grow horizontally and promote the formation of flower buds. You can also twist the tip, but you should master the twist when twisting the tip, so that the cortex and phloem are injured and the xylem is not broken, which is what the masses say.