How to Achieve High Yields After Top-Grafting Pear Trees? Master These Six Techniques
As the fruit market gradually becomes saturated, some old varieties face being phased out, and replacing the old with the new and introducing and top-grafting superior varieties is imperative. The top-grafting and its key technical points are as follows:
Master the best grafting time. Late February to early March each year is the best grafting window; too early makes survival difficult, while too late means the scions bud late and the branches grow slowly, so they cannot become flower-bearing branches in the same year.
Get the ratio of yield to graft unions right. Practice has proven that grafting with many unions significantly increases trunk circumference, crown diameter and total branch volume, basically maintaining the balance between the aboveground and belowground parts of the tree and the root system's absorption and supply capacity, bringing the grafting survival rate to above 99%. The number of graft unions is determined by the tree's original yield; generally, for a large tree with an original yield of more than 200 kg, use one scion per 500 g of fruit; for trees under 200 kg, top-graft at a ratio of one scion per 1000 g of fruit.
Use horizontal-branch grafting. Before top-grafting, first clean up the branches of the tree, thinning out some large branches and overly dense branch groups according to the tree's shaping requirements. Cut off all the branches and trunks to be grafted according to their branching, smooth the cuts and then graft; do not cut one and graft one, to avoid inconvenience in movement or damaging already grafted scions. The grafting methods use cleft grafting and cut grafting; according to the thickness of the rootstock branch, use short scions with 2 to 3 buds and long scions with 3 to 5 buds. When grafting, change the traditional upright-branch grafting and choose horizontal branches as rootstocks, inserting the prepared scions onto horizontal or drooping branches to facilitate the accumulation of organic nutrients, and try to avoid grafting directly on upward-growing branches. Wrap the graft union with film, and seal the top of the scion with wax to prevent water loss.
Do not pinch off the growing tips; untie at the right time. That is, the new shoots that grow out after grafting in the same year must not have their tips pinched off, as this helps the branches terminate growth and readily form flower buds. Only twist the tips of vigorous branches or competing branches. In early July, after the graft union has healed, untie it; those whose unions have not yet healed should continue to be wrapped, and untie them only after they have fully healed.
Set yield by the tree, set fruit by the flowers. For fruit trees grafted in the same year, during winter pruning focus on light pruning, delayed pruning and keeping more branches. In the flowering period of the second year, according to the tree age, the size of the crown and the load borne by each branch, achieve “set yield by the tree, set fruit by the flowers”.