What are the improved methods for pear tree cultivation?

For pear trees with poor quality and low yield, the usual method is to cut down the original plants. Planting improved, vigorous seedlings for renewal means it takes five years before they come into production. If the top-grafting and variety-change technique is used, however, the original tree framework can be utilised to rapidly form a canopy, achieving a per-tree yield of about 60 kg the following year, about 170 kg in the 3rd year, and further increases in subsequent years. The key points of this top-grafting technique are introduced below for reference.

1. Grafting time Young and young-mature low-yield, low-quality trees can be top-grafted for variety change; senescent trees and severely pest- or disease-affected low-yield, inferior-quality trees are not suitable for top-grafting and variety change and should be felled and replanted with new seedlings. Top-grafting for variety change can be carried out in spring and autumn, with grafting in March-April and August-September being better; because at this time the scion buds are plump and full, and sap flow is vigorous; meristematic tissue is active, callus tissue forms quickly, the survival rate is high, and the scion grows fast. The suitable temperature for grafting is 20-26°C, so grafting should be done in the early morning and late afternoon of sunny days and on cloudy days.

2. Scion collection Select plants that are suited to the local climate and site conditions, grow vigorously, are free of pests and diseases, bear abundantly, and have excellent quality as mother trees for scion collection. The scions should be grafted immediately after collection. Cut one-year-old vegetative branches or fruiting branches with plump buds facing the sun from the middle and outer part of the mother tree canopy as scions. The collected scions should have their leaves removed while retaining the petioles, be tied into small bundles, and have their bases wrapped in damp toilet paper to retain moisture; during transport and grafting they must be protected from wind and sun.

3. Selection and retention of rootstock branches Requirements should be adapted to the tree, making full use of the original framework and main branches and shoots; for the selected rootstock branches, main branches should be left long and side branches should be left short, generally cutting into rootstock heads at a point where the branch diameter is about 5 cm. For young small trees, 15-30 rootstock branches can be selected; for young to medium trees, 30-60 rootstock branches can be selected; for vigorous mature large trees, 60-80 rootstock branches can be selected. The cut surface of the rootstock branches should not be too large, so as to facilitate healing of the cut and early formation of the canopy.

4. Grafting operation There are many methods for top-grafting pear trees, among which bark grafting is mostly used in spring; budding is mostly used in autumn. For bark grafting, cut a long slant about 8 cm long at the lower end of the scion, then cut two short slants each about 0.6 cm long at the rear end (making it arrow-shaped), and cut off the upper end after leaving 3-5 buds; then cut off the rootstock branch and smooth its cut surface, make a cut equal in length to the scion cut surface on its smooth side, deep to the cambium; pry open the bark at the cut on the rootstock head, insert the long cut surface of the scion inward between the xylem and phloem of the rootstock head; finally bind the union tightly with plastic film tape. For the budding operation, the conventional “T”-shaped budding method can be used, and the bud patch is best 2-3 cm long.

5. Post-grafting management After grafting, promptly remove sprouts on the rootstock; to promote growth of the grafted plant. After the union has healed firmly, remove the binding tape; to avoid affecting growth of the grafted branch. For budded ones, after sprouting, cut off the rootstock shoot from 0.5-1.0 cm above the bud. When the scion grows to 50 cm, it should be pinched and tied with a small stick for support, to avoid wind breakage. Cultivation and weeding, tree management, pest and disease control, and fertilisation and irrigation should be strengthened, to promote formation of a high-yielding canopy, thereby achieving early fruiting and high yield.