Detailed Explanation of Key Techniques for Autumn Top Grafting and Variety Change in Pear Trees
Grafting time
In production, large-scale top grafting of pear trees to switch to improved varieties is generally carried out from early August to late September in autumn, that is, during the period after summer shoots stop growing and before autumn shoots stop growing. During this period, the grafting survival rate is high, the cost is low, and the effect is good; usually only one year is needed.
Varieties are adjusted properly, and the canopy recovers quickly and the orchard appearance is neat and standardized.
Grafting method
Autumn top grafting of pear trees mostly uses the method of bud grafting with wood. This method is simple to operate and easy to promote. Specific steps:
1. Selection and retention of grafting framework: according to the original tree structure or in combination with adjusting the tree shape, select main branches and the central leader extension head that have good growing orientation, layer spacing, and opening angle and are robust as grafting objects. Choose 3-5, 6-9, or 12-15 branches according to the situation.
2. Grafting position: the grafting position on main branches is selected 20-30 cm from the central leader, smooth and flat, on the upper side and easy to operate; the grafting position on the central leader is selected at the place where the top should be cut back.
3. Cutting the grafting position: in order from top to bottom, at the selected position, cut smoothly with a knife from top to bottom (central leader extension head) or from outside to inside, with a cut surface about 2.5-3 cm long, deep to the xylem but preferably without damaging the xylem.
4. Cutting the scion bud: hold the upper part of the scion bud tightly with the left hand, cut smoothly inward with a knife from 0.5 cm above the bud eye, with a cut surface about 2-2.5 cm long; the cut surface on the back of the bud eye should carry a little wood, about 1-2 mm thick, then make a horizontal cut 2 cm below the bud eye down to the vertical cut surface.
5. Grafting method: quickly remove the scion bud with the left hand, and at the same time use the right hand to cut off 0.5 cm of the upper part of the bark lifted open at the grafting position; with both hands working together, insert the bud piece, paying attention that the edge of the grafting incision slightly shows white and matches the upper arc surface of the bud piece. If the grafting incision is much wider than the bud piece, align and match on one side. When cutting off the upper part of the bark lifted open at the grafting position, depending on the size of the bud piece, use two cuts to remove part of the upper bark. After inserting the bud, press tightly with the hand and then tie it tightly, exposing the bud eye.
Management after grafting
Management after top grafting of pear trees aims to protect the grafted buds so as to produce strong shoots the following year. In autumn, the main practices should be preserving leaves, controlling fertilizer, and draining waterlogging. In winter pruning, remove excess branches and shoots, and cut back two-thirds of the branches above the grafted buds on main branches. In the second year, half a month before spring sprouting, leave one lateral small branch above the grafting position and then cut back to expose the grafted bud, so as to promote strong shoots. When cutting back and thinning large branches, attention should be paid to using chemicals to protect the wounds. During the growing season, carry out shaping by bud rubbing, pinching, branch thinning, branch bending, and branch pulling, strengthen fertilizer and water management and pest and disease control, expand the nutritional area as soon as possible, maintain the balance between roots and canopy, and ensure that the canopy and tree vigor recover strongly.