Detailed Explanation of the Cleft Grafting Method and Top Grafting (Topworking) Technique for Plum Trees

1. Preparation before grafting:

Generally in February, cut healthy, pest-free 1-year-old branches as scions. It is best to use fully mature, plump-leaf-budded, well-developed branches from the upper outer canopy of trees that have already fruited. Cut them into 15-20 cm segments (with 3-5 buds), heat paraffin in a water bath to 90-100°C, quickly dip the upper ends of the segments in melted wax, and after cooling, bundle them into groups of 50-100 per variety, attach labels, and store them in containers at 3-5°C with 70%-80% humidity.

2. Grafting period and method:

Grafting is carried out when the rootstock buds begin to swell but have not yet leafed out. Generally, strong vigorous branches within 3 years of branch age are selected for top grafting, and the top-graft branches are cut to leave 20-30 cm. First, use a sharp knife to cut one side of the scion into a large cut surface 2-3 cm long, and the other side into a small cut surface 1-1.5 cm long. The cut surfaces must be smooth; the long cut surface should be cut down to the pith line, and the short cut surface should be determined according to the rootstock incision. At a smooth spot near the base of the branch to be top-grafted, choose a position with a suitable angle, and use a sharp knife to make an oblique downward cut, reaching 1/3-1/2 deep into the rootstock, making the cut longer than 2 cm. Then quickly insert the scion with its long cut surface facing inward, align the cambium on the outer side, and at the same time cut off the part of the rootstock above the incision, then wrap the wound tightly and securely with elastic plastic film strips. The rootstock incision should not be cut to or past the pith line, otherwise it is not conducive to growth and development.

3. Management after grafting:

After top grafting, promptly remove sprouts on the rootstock. About 15 days after grafting, check whether the grafts have survived, and promptly re-graft those that have not. When new shoots on the top-grafted branches grow to 20-30 cm, set up wooden stakes, tie the stakes tightly to the rootstock, then secure the new shoots to the stakes with rope to prevent wind damage, and loosen the plastic film ties to prevent constriction marks. Promptly adjust the angle and direction of the main branch extension shoots. For auxiliary branches, when new shoots grow to 40-50 cm, leave 20-30 cm and pinch off the tips; generally pinch 2-3 times, with the last pinching in mid-September. Strengthen fertilizer and water management and pest and disease control.