What are the latest grafting methods for fruit trees?

Fruit tree grafting is one of the methods of asexual propagation of fruit trees, that is, taking a branch or bud from a plant of a superior variety and joining it to a suitable part of another plant so that the two combine to form a new plant. The new plant propagated by grafting can not only maintain the superior traits of its mother plant but also make use of the favorable characteristics of the rootstock (stress resistance, adaptability, early fruiting, etc.). Now let us take a look at what grafting methods there are for fruit trees!

Bark-removed side grafting

1. Technical characteristics: Bark-removed side grafting is to cut away 1 strip of bark from the rootstock and attach the scion at the bark-removed spot. It is usually used when the rootstock interface is large and 2 or more scions are grafted at the same time. This grafting method is slower, but the fit is tight and the survival rate is high. The grafting period also needs to be arranged when the rootstock bark can be slipped.

2. Rootstock cutting: Saw off the rootstock at a straight place without knots, then use a knife to smooth the wound. Then cut away a piece of bark on the rootstock equal in size to the scion wound, about 4 cm long, exposing the xylem and cambium. The number of cuts on the rootstock can be determined by the thickness of the rootstock. A medium rootstock can have 2 cuts, and a larger rootstock can have 3 to 4 or more than 4. Each cut takes 1 scion.

3. Scion cutting: Keep 2 to 3 buds on the scion, cut a slanted surface at the lower end, about 4 cm long. When starting the cut, go deep into the xylem, then cut straight down flat and remove about 1/2. The front end does not need to be sharpened.

4. Rootstock-scion joining: Press the cut surface of the scion tightly against the bark-removed cut on the rootstock and leave 0.5 cm of the upper part of the scion wound exposed.

5. Wrapping and management: First tie tightly with a plastic strip, then smear mud at the cut (or not), then cover with a plastic bag to keep warm and moist. After sprouting, first cut a small hole in the bag for ventilation, and later remove the plastic bag to allow the new shoot to grow.

Cleft grafting

1. Technical characteristics: Cleft grafting means making a small split in the rootstock and inserting the scion into the split. It is an ancient and main method of branch grafting carried out in spring. Because it is not necessary to graft when the rootstock bark is slipping, the grafting period can be earlier. In cleft grafting, the rootstock interface tightly grips the scion, so after the graft survives, the scion is not easily broken by wind. A medium-thick rootstock is suitable. If the rootstock is too thick, it is not easy to split, and the clamping force of the split is too great, which easily damages the scion. If the rootstock is too thin, the interface does not clamp tightly, and the scion is also not conducive to survival. However, cleft grafting is more complicated to operate than bark grafting, requires more tools, and for some old trees such as jujube trees, whose xylem grain is not straight, it is not easy to make a straight split, so this method is not suitable.

2. Rootstock cutting: Saw off the rootstock at a place where the bark is straight and without knots, and smooth the wound with force. Then in the middle of the rootstock, use a wooden mallet or wooden stick to slowly tap the splitting knife downward to form a split. For young branch cleft grafting, only a budding knife is needed to make the split from the middle of the branch.

3. Scion cutting: The scion should first be wax-sealed, leaving 2 to 3 buds, and one cut should be made on each of the opposite lower sides to form a wedge shape. If the rootstock is relatively thin, when cutting the scion, its outer side should be slightly thicker than the inner side. The outer side of the wedge-shaped wound of the scion connects with the rootstock cambium, while the inner side does not. If the rootstock is relatively thick, the left and right sides of the wedge should be equally thick to avoid damaging the outer joining surface due to excessive clamping force. Young branch cleft grafting requires the scion and rootstock to be equal in thickness so that both the left and right sides connect. The cut surface length of the scion is generally 4 to 5 cm. The cut surface should be long and flat, and the angle should be appropriate so that both the upper and lower parts of the rootstock at the interface can connect with the scion.

4. Rootstock-scion joining: Pry open the split of the rootstock, then insert the scion into one side of the split. The key at this time is to align the cambium of both parties. It is best to align the cambium on both the left and right outer sides of the scion with the cambium on both sides of the rootstock split. If alignment on both sides is impossible, then aligning one side and placing the other side outward against the rootstock phloem is also acceptable. Young branch cleft grafting requires the scion and rootstock to be equally thick so that the cambium on the front, back, left, and right sides of the scion and rootstock basically connect. When joining, do not insert all of the scion wound into the split; instead leave more than 0.5 cm exposed, which is beneficial for healing. If the entire scion wound is inserted into the split, then on one hand the upper and lower cambium cannot align accurately, and on the other hand the healing surface forms a lump below the saw cut, causing poor healing later and affecting lifespan.

5. Wrapping and management: For medium or relatively thin rootstocks, insert 1 scion into the split and wrap it with a plastic strip 1.5 times the diameter of the rootstock and 40 to 50 cm long. The split, wound, and exposed area must all be wrapped tightly and tied firmly. If the rootstock cut is relatively thick, then 2 scions can be inserted on both sides of the split. After insertion, first smear mud to seal the split, then cover with a plastic bag and tie it tightly. After the scion buds sprout, first cut a small opening in the bag for ventilation, and after the buds grow, remove the plastic bag. For young branch cleft grafting, such as grape grafting, after cleft grafting use a 1.5 cm wide plastic strip to tie the interface tightly and firmly, then seal the scion, leaving only the petiole and buds exposed to reduce scion water evaporation.

Cut-and-side grafting

1. Technical characteristics: Cut-and-side grafting is a grafting method with the characteristics of both cut grafting and side grafting. It is suitable for spring branch grafting of small rootstocks in nurseries and has the characteristics of fast grafting speed and high survival rate.

2. Rootstock cutting: Cut off the rootstock at about 5 cm above the ground, then use a knife to make a deep inward and downward cut about 3 cm from the cut, about 1 cm long. Then cut vertically downward at the cut. The width of the two cuts is basically equal to the diameter of the scion so that the two cuts meet, and remove the two pieces of rootstock to expose the cut surface.

3. Scion cutting: The scion is wax-sealed in advance. When cutting, leave 2 to 3 buds on the upper part, cut a large slanted surface at the lower end, 4 to 5 cm long, then cut two small slanted surfaces on the back side, about 1 cm long.

4. Rootstock-scion joining: Place the large cut surface of the scion against the cut surface of the rootstock, insert the lower end tightly, and make the cambium of the rootstock and scion connect on the left, right, upper, and lower sides. If the two sides cannot be aligned, then one side must be aligned.

5. Wrapping and management: First use a plastic strip to tie the rootstock and scion tightly, then smear mud at the saw cut, then use a plastic bag to cover the saw cut and scion, and tie it tightly.

Approach grafting

1. Technical characteristics: Approach grafting means that during grafting the rootstock and scion are placed together and joined. In nature, naturally joined branches and two trees growing together are also a kind of approach grafting. Approach grafting can be carried out during the dormant period or during the growing period. Because both the rootstock and scion are grafted without being detached from the plant and both have their own root systems, the survival rate of grafting is high. Although grafting is relatively simple, placing the rootstock and scion together is quite difficult, so it is often used in some special situations, such as saving dying trees and potted fruit trees.

2. Key operating points: For the cutting and joining of rootstock and scion, according to differences in the thickness of the rootstock and scion, approach grafting can be divided into 3 types: simple approach grafting, tongue approach grafting, and inlay approach grafting.

① Simple approach grafting: Simple approach grafting is also called splice approach grafting. Make one wound each on the rootstock and scion at corresponding positions, 3 to 4 cm long. The widest part of the wound is about equal to the diameter of the scion, and the wounds on both sides are equal in size. The cutting knife must be sharp. Bend the branch with the left hand and cut the wound with the right hand so that the wound is flat and straight. If the branch is not bent, it cannot be cut. Then join the wounds of both sides together, and tie the joined part tightly with a plastic strip about 1 cm wide.

② Tongue approach grafting: The rootstock and scion are equal in thickness. Make one tongue-shaped cut on each at suitable positions, one from top to bottom and the other from bottom to top, about 3 cm deep, reaching nearly 1/2 of the diameter, and peel off part of the bark outside the small tongue (not cut when grafting cucurbits). When cutting the small tongue, bend the branch with the left hand and cut with the right hand, which makes operation easier. When joining, as with tongue grafting, the tongue-shaped parts are inserted into each other, and then the joined part is tied tightly with a plastic strip about 1 cm wide.

③ Inlay approach grafting: This method is used for grafting under conditions where the rootstock is thick and the scion is thin. First cut a groove in the rootstock, with width the same as the scion diameter and length 4 to 5 cm, and dig out the bark. The scion, as in approach grafting, has one wound cut, about 4 cm long. When joining, place the scion wound into the rootstock groove so that they inlay each other. Then, use a plastic strip about 1 cm wide to tie the joined part tightly.