Detailed Explanation of the Key Techniques for Top-Grafting and Cultivar Conversion of Chinese Bayberry

1. Technical essentials (1) Timing: In Zhejiang, mid-March to early April is suitable.

(2) Scion selection: National regulations stipulate that any variety that has passed appraisal and recognition may be used as a top-grafting variety, but the most widely used one in various regions is: Dongkui Chinese bayberry; because in addition to its exceptionally large fruit, high quality, tolerance to storage and transport, and the attractive high market price, it also has good compatibility. The scions used for top-grafting should be selected from 2-year-old mature branches in the middle and upper part of the canopy; the branches should have already faded from green to gray, with a thickness of 0.8-1.2 cm. Note: the tree must not have been treated with excessive paclobutrazol, otherwise growth will stall after grafting.

(3) Rootstock selection: Suitable rootstocks for Chinese bayberry include: Shuimei, Cimei, Hongmei, and various seedling Chinese bayberry trees; the tree age is best within 15 years, with a good root system, smooth bark, and few injuries. Note: in recent years, trees that have been treated with excessive paclobutrazol cannot be top-grafted.

(4) Specific method: Use the cut-grafting method with a horseshoe shape, long scions, and full film wrapping. Scion length: 7-10 cm; scion cut surface: 2-3 cm on the front side and 0.5-1 cm on the back side, and it is required to be smooth. On the canopy, select side branches within 2 m in height and 3-4 cm in thickness for top-grafting, and leave about 5% nurse branches at the lower part of the canopy (also called “water-guiding branches” and “water-retaining branches”). Generally, for bearing trees over 10 years old, 20-25 scions can be top-grafted per tree; for young trees under 10 years old, 10-15 scions can be top-grafted per tree; the distance between graft unions should be more than 50 cm, so as to avoid excessive branches causing canopy shading. After grafting, wrap all wounds with plastic film; after survival, the scions emerge from the gaps in the film.