How to Graft New Varieties of Landscape Plants? Master These Five Key Techniques

Grafting of landscape trees is a common artificial plant propagation method in horticulture. It uses the ability of two different plants to unite, joining the branch or bud of one plant onto the stem or root of another plant so that they heal together and form an independent new individual. It can maintain the excellent characteristics of a variety, enhance the resistance and adaptability of the scion variety, change the plant shape, and advance the age at which flowering begins.

During grafting, the following five points should mainly be noted:

1. Compatibility between rootstock and scion

So-called compatibility refers to the healing ability of the rootstock and scion after grafting. The degree of compatibility is determined by the plants' genetic relationship, physiology, morphological structure, hereditary characteristics, and the influence of their internal contents. For example, when grafting fruit peach, if wild peach is used as the rootstock, the two belong to the same genus, so compatibility is relatively strong and survival after grafting is easy; but if Sophora japonica, which belongs to a different family, is chosen as the rootstock, they are incompatible and the graft will not survive.

2. Selection of rootstock and scion

When selecting the rootstock, the following conditions should be noted:

(1) Good adaptability to the climate, soil, and other environmental conditions of the cultivation area, with a well-developed root system and strong growth, using a middle-aged or young tree;

(2) Free of pests and diseases, with good resistance to drought and waterlogging, low temperature, air pollution, and so on;

(3) Sufficient sources and easy propagation, able to meet special needs in application, such as standard vigor, dwarfing, and thornlessness. In addition, the scion should also be selected from vigorous, pest- and disease-free growth, and one-year-old or current-year semi-lignified branches are best. If the scion is too old, healing and survival will be poor or survival will be difficult.

3. The scion should be grafted as soon as it is cut

The scion must not be left for too long after cutting, to prevent water loss and drying out, which affect the survival rate. For example, if five-needle pine scions are cut in winter from a distant place, they should be temporarily placed indoors, but attention should be paid to moisture-retaining storage. For peach budding, because the leaf buds are relatively small, even more attention should be paid to grafting as soon as the scions are cut. Grafting should be done in a windless, shaded place to prevent sun and rain from causing the scion to lose water and dry out, which affects survival.

4. Grafting time:

In general, the grafting time should be chosen when both the scion and rootstock are in the bud-swelling or growth period; too early or too late is poor for healing. For fruit peach and five-needle pine, grafting can also be carried out in July, when the plants are in a slow-growth period.

5. Alignment of the cambium:

A plant stem is composed of the surface layer, cortex, phloem, xylem, and pith. Among these, the cambium is the key to graft healing. If the cambium between the rootstock and scion is aligned and closely joined, the graft is likely to survive. Especially when the rootstock is thick and the scion is thin, even more attention should be paid to aligning the cambium.

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Complete Guide to Learning Plant Grafting Knowledge

Complete Guide to Learning Plant Grafting Knowledge

1. The significance and role of grafting:
In production practice, various grafting methods for economic crops such as fruit trees, vegetables, and flowers have already been widely applied.
In recent years, newly developed techniques such as shoot-tip grafting, detached stem-segment grafting, test-tube seedling grafting, callus grafting, cell grafting, and grafting of the model plant Arabidopsis thaliana have also been receiving increasing attention;
Botanists' research on the cytology, physiology and biochemistry of the graft union development process, the interaction mechanisms between scion and rootstock, and the mechanisms of graft compatibility will certainly bring new scientific research results to our lives.

01. The significance of grafting:
Grafting refers to the purposeful use of the ability of two plants to unite, joining the branch or bud of one plantontothe stem (branch) or root of another plant, so that they heal and grow together and form an independent plant, as a propagation method.
In production practice, grafting also has very many examples of increasing economic value, such as:
Ordinary dawn redwood is worth one yuan; but through grafting, after being cultivated into golden-leaf dawn redwood, its economic value increases by more than 20 times;
An ordinary large-leaf privet tree is worth a few tenths of a yuan; but through grafting, after being cultivated into colored-leaf zhen tree, its economic value is as much as nearly a hundred times higher.
It can thus be seen that grafting is of very important significance for variety improvement and the increase of economic value.
Grafting is of great significance for the propagation of some fruit trees that do not produce seeds (such as persimmon and some citrus varieties).
Grafting can not only maintain the excellent traits of the scion variety, but also make use of the favorable characteristics of the rootstock, achieving earlier fruiting, enhancing cold resistance, drought resistance, and pest and disease resistance, and can also economically use propagation materials and increase the number of nursery stock.
It is commonly used in the propagation of fruit trees, forest trees, and flowers; it is also used in the seedling cultivation of melon-family vegetables.
Grafting is divided into two major categories: branch grafting and bud grafting. The former is preferably carried out in spring and autumn, with a higher survival rate especially in spring; the latter is preferably carried out in summer.
The branches and buds used for grafting are called scions or scion buds; the plant (rootstock plant, root segment, or branch segment) that bears the scion or scion bud is called the rootstock.
Using a branch as the scion is called branch grafting; using a bud as the scion is called bud grafting.
The nursery stock obtained through graft propagation is called grafted nursery stock.
The difference between grafted nursery stock and other vegetative propagation nursery stockisthat it relies on the root of another plant; therefore, grafted nursery stock is "stock-rooted nursery stock."
02. The history of grafting:
Grafting originated in nature. In nature, we can often see the phenomenon of natural grafting, that is, when tree branches grow interlaced, due to wind and rain, the branches rub against each other and are injured, and their injured surfaces naturally heal together, forming what people often call "union trees" or "union branches"; when the roots of two trees grow close together, over time "union roots" also form.
This union phenomenon is natural approach grafting, and it was further discovered that plants forming union branches or union roots generally grow vigorously.
People were inspired by "union branches" and artificially cut the bark of two tree branches and pressed them together, which produced grafting.
From this it can be seen that grafting first involved approach grafting, and only later developed into many other grafting methods.
China was the first country in the world to apply grafting (branch grafting) technology. The earliest record related to grafting is seen in:
The Book of Documents, Tribute of Yu: "Oranges crossing north of the Huai River become trifoliate orange." It is inferred that the orange was grafted onto trifoliate orange; when moved north of the Huai River, the orange developed from trifoliate orange could not tolerate cold and froze to death, while the cold-tolerant trifoliate orange sprouted again, and the orange turned back into trifoliate orange. It is generally said that China's grafting technology has a history of 3000 years, and this is inferred on that basis.
China's clear record of grafting technology is found in the Fan Shengzhi Shu written by Fan Shengzhi in the 1st century BC, which contains a detailed account of using approach grafting to produce large gourds.
By the 5th century AD, China's grafting technology had developed to a considerable level. During the Northern Wei Dynasty, Jia Sixie's Qimin Yaoshu already contained grafting methods for pear and persimmon; in the Southern Song Dynasty's Chen Fu Nong Shu, there was mulberry grafting; Ouyang Xiu's Luoyang Peony Record contained peony grafting;
Later, the grafting methods in Wang Zhen Nong Shu, Qunfang Pu, and Hua Jing were already very detailed, and many techniques are still in use today.
03. The role of grafting:
Graft propagation is a very important method in the production of landscape plant nursery stock.
In addition to the advantages of general vegetative propagation, it also has roles that other vegetative propagation methods cannot perform:
01) Maintaining the excellent characteristics of plant quality and improving ornamental value:
The scions used in landscape plant graft propagation all come from mother plants with excellent quality;
Their heredity is stable, and in landscaping and beautification, the ornamental effect is superior to that of seed-propagated plants.
Grafting can preserve the excellent traits of plants, and this has long been widely applied in fruit tree production.
For a long time, most fruit trees have been propagated by grafting.
Although after grafting they are affected by the rootstock to varying degrees, they can basically maintain the excellent traits of the mother plant.

02) Increasing resistance and adaptability:
The rootstocks used in grafting mostly adopt wild species, semi-wild species, and locally native types.
Such rootstocks have strong adaptability and can grow and develop normally under very poor natural conditions.
Once they are used as rootstocks, they can enable the grafted variety to adapt to unfavorable environments. Through the physiological influence of the rootstock on the scion, they improve the resistance of the grafted nursery stock, expand the cultivation range, and can enhance cold resistance, drought resistance, saline-alkali resistance, and pest and disease resistance. For example:
Wild jujube is tolerant of drought and barren conditions; using it as a rootstock to graft jujube increases jujube's ability to adapt to barren mountainous land;
Chinese wingnut is tolerant of water and moisture; grafting walnut onto it expands the cultivation range of walnut on wet land;
White poplar is prone to cold damage in the Hohhot area of Inner Mongolia and is difficult to plant locally; using the local small-leaf poplar as a rootstock for grafting allows it to overwinter safely;
Grafting persimmon onto Diospyros lotus can improve cold resistance;
Grafting apple onto crabapple can resist cotton aphid;
Grafting ornamental peach onto mountain peach gives vigorous growth and easily forms tall plants; grafting it onto Shouxing peach forms short plants;
Grafting virus-free citrus shoot tips onto virus-free, seedling rootstocks cultivated aseptically can produce virus-free citrus clones.
03) Advancing flowering and fruiting:
Grafting can make flower-viewing, fruit-viewing, and fruit trees flower and fruit earlier, and make timber tree species mature earlier.
The reason grafting promotes earlier flowering and fruiting in ornamental trees and fruit trees is mainly that the scions are collected from mature trees that have already entered the flowering and fruiting stage. After such scions are grafted, once they heal and resume growth, they will soon flower and fruit. For example:
Using seeds to propagate Chinese chestnut, it takes 15 years before it can bear fruit, with an average yield of 1-1.5 kg of chestnuts per plant.
But grafted Chinese chestnut can flower and fruit in the second year, and after 4 years the yield per plant can reach more than 5 kg;
Citrus seedlings require 10-15 years before they can bear fruit; grafted nursery stock can bear fruit in 4-6 years;
Apple seedlings take 6-8 years to bear fruit; grafted nursery stock takes only 4-5 years.
In terms of timber tree species, grafting improves the vitality of trees and accelerates growth speed, thereby making the trees mature earlier.
"Graft green poplar onto white poplar, and in the same year it grows as long as a hoe handle" refers to trees growing faster and maturing earlier after grafting.
04) Overcoming difficulty in propagation:
Some plant varieties in landscapes, because of breeding purposes, have no seeds or very few seeds for propagation, and cutting propagation is difficult or develops poorly after cutting; using graft propagation can better complete the work of propagation and seedling raising. For example, double-petal varieties among landscape trees, and seedless grapes, seedless citrus, and persimmon among fruit trees.
05) Expanding the propagation coefficient:
By using seed propagation for the rootstock, a large number of rootstocks can be obtained. In this way, a small amount of scion can be used to obtain a large number of nursery stock in a short time, especially for new varieties from bud sports; using grafting can rapidly expand the number of the variety.
06) Breeding new varieties: Grafting to breed new varieties is shown in the following three aspects:
A. Using "bud sports" to breed new varieties:
A bud sport usually refers to variation occurring in one bud and the branch produced by one bud.
This variation is a mutation occurring in the somatic cells of the plant bud's meristem.
Bud sports often show new excellent traits, such as high yield, improved quality, and enhanced pest and disease resistance.
People graft the branches after bud sport, and then carefully manage them, and can breed new varieties. For example:
"Dragon-claw pagoda tree" was selected and bred by grafting using a bud sport of Sophora japonica, and has drooping branches;
The "Red Star" apple variety was selected and bred by grafting using a bud sport of the "Delicious" variety. Compared with the original variety, it has the advantages of earlier coloring and rich, bright red color.
B. Carrying out graft breeding:
Although both graft breeding and graft propagation require grafting, the two are two different concepts.
Graft propagation: it is a propagation process. It uses the grafting method to maintain the original excellent traits and enhance adaptability and earlier flowering, fruiting, or maturation.
Therefore, graft propagation basically does not produce variation or new traits.
Graft breeding: it is a process of asexual hybridization. It also uses the grafting method, but it is intended, through the mutual influence between scion and rootstock, to cause the scion or rootstock to vary, thereby producing new excellent traits.
To carry out graft breeding, it is necessary to determine the cross combination and select the scion and rootstock. For example:
Choose as the scion a plant with a short phylogenetic history, young individual development, traits not yet fully developed, and heredity not yet fixed,
and choose as the rootstock a plant with a long phylogenetic history, individual development in its prime, traits already fully developed, and heredity already fixed.
After grafting, keep the rootstock branches and leaves and reduce the scion branches and leaves.
In this way, it is possible for the rootstock to influence the scion and cause the scion to produce some kind of variation.
After the variation appears, through further cultivation, it is possible to breed a new variety.
C. Carrying out asexual approaching to create conditions for sexual distant hybridization:
Sexual distant hybridization often has the situation of cross incompatibility or hybrid sterility. If the two parents are grafted beforehand so that the two sides physiologically approach each other, and then pollination and hybridization are carried out, success can often be achieved. For example:
Apple branches are grafted onto the crown of a pear; after flowering, they are pollinated with pear pollen, obtaining an intergeneric hybrid of apple and pear. Without grafting, fertilization would not be possible.
07) Restoring tree vigor, treating and rescuing wounds, supplementing missing branches, and renewing varieties:
For aging trees, the advantages of a strong rootstock can be used through methods such as bridge grafting and root grafting to promote growth and restore tree vigor.
If the crown becomes lopsided or hollow in the middle, grafting can adjust the development direction of the branches, making the crown fuller and the tree shape more beautiful.
For plants with poor varieties, grafting can be used to replace the variety.
For dioecious plants, grafting can be used to change the sex of the plant.
Grafting can also make one tree have multiple species, multiple heads, and multiple flowers, improving its ornamental value.
04. Influencing factors:
The main factor affecting graft survival is the compatibility between the scion and rootstock, followed by grafting technique and post-grafting management. So-called compatibility means that the scion and rootstock are the same or similar to each other in internal tissue structure, physiology, and heredity, and thus are able to unite with each other. High compatibility means a high graft survival rate. Conversely, the survival rate is low. Generally speaking, the closer the genetic relationship between plants, the stronger the compatibility. For example, apple grafted onto sand pear; pear grafted onto Pyrus betulifolia and Pyrus ussuriensis; persimmon grafted onto black date; walnut grafted onto Manchurian walnut all have very good compatibility.
05. Limitations of grafting:
The above grafting can improve or restore the greening and beautification effects of some trees.
However, graft propagation also has certain limitations and shortcomings. For example:
Graft propagation is generally limited by genetic relationship and requires strong compatibility between rootstock and scion; therefore,
some plants cannot be propagated by grafting;
Monocotyledonous plants are difficult to graft successfully due to the structure of their stems.
In addition, grafted plants have a shorter lifespan; and grafting propagation is also relatively complicated in terms of operational technique and requires a high level of skill;
Some also require the prior cultivation of rootstock, which involves a relatively large input of manpower and material resources.

II. The principle and process of successful grafting:
After the scion and rootstock are grafted, the key to whether they can survive lies in whether the tissues of the two heal together, and the main sign of healing is the connection of the vascular tissue system.
The success of grafting mainly depends on the compatibility between the rootstock and the scion, as well as the cell growth, division, and cambium regeneration capacity around the wound at the union site.
The cambium is a thin-walled cell layer with strong regenerative capacity located between the xylem and the phloem (see the figure below for details).

Longitudinal and cross sections of a branch: 1. Xylem; 2. Pith; 3. Phloem; 4. Epidermis; 5. Cambium

Under normal circumstances, the thin-walled cell layer undergoes cell division, forming xylem inward and phloem outward, causing the tree to grow thicker; after the tree is wounded, the thin-walled cell layer also has the function of forming callus tissue to protect the wound. Therefore, after grafting, the cambium thin-walled cells of the rootstock and scion at the union site each divide to form callus tissue, gradually filling the gap at the union, so that the new cells of the scion and rootstock come into close contact, forming a common cambium that produces phloem outward and xylem inward, and the two heterogeneous parts are thereby united into one. In this way, --
The root system of the rootstock absorbs water and inorganic nutrients from the soil to supply the scion;
The branches and leaves of the scion produce organic nutrients that are transported to the rootstock, and the two combine to form a new individual capable of independent growth and development.
It can thus be seen that in terms of technical measures, besides considering compatibility based on the genetic characteristics of the tree species;
The key to successful grafting is the close union of the cambium of both the scion and the rootstock, and the larger the union surface, the easier it is to survive.
Practice has shown that to make the cambium of the two come into close union, --
When grafting, the contact surfaces between them must be made smooth; the cambium must be aligned, clamped tightly, and bound firmly. See the figure below for details:

III. Factors affecting grafting success:
The main factors affecting grafting success include the compatibility between the rootstock and scion; the quality of the rootstock and scion; external conditions and grafting technique, among the following aspects:
01. Internal factors affecting grafting success: These internal factors include the compatibility between the rootstock and scion; the vitality of the rootstock and scion and the biological characteristics of the tree species, etc.
01) Compatibility between rootstock and scion: Grafting compatibility is the ability of the scion and rootstock to heal and grow after grafting. Specifically, it refers to the ability of the scion and rootstock to be mutually compatible and unite because they are identical or similar to each other in morphology, structure, physiology, and heredity.
① The degree of grafting compatibility is manifested in --
A. In morphology and structure, it is the degree of similarity in the volume and structure of each other's cambium and thin-walled cells;
B. In physiology and heredity, it is the degree of similarity in the growth rate of cambium or other tissue cells and in the raw materials and products required for each other's metabolic activities.
Grafting compatibility is the most basic condition for successful grafting.
No matter which plant is used, and no matter which grafting method is used, a certain degree of compatibility must exist between the rootstock and the scion.
The higher the compatibility, the higher the grafting survival rate; conversely, the smaller the possibility of successful grafting.
② The strength of grafting compatibility is related to the closeness of the kinship relationship between the trees. The general rule is that the closer the kinship relationship, the stronger the compatibility. Therefore, --
Grafting between varieties is the easiest to succeed; between species it is next; between different genera it is next again. Between different families, it is more difficult.
02) The vitality of the rootstock and scion and the biological characteristics of the tree species: The formation of callus tissue is related to the plant species and the vitality of the rootstock and scion.
Generally speaking, if the rootstock and scion grow robustly, their vegetative organs are well developed and substantial, their internal nutrients are abundant, their growth is vigorous, and their cambium cells divide most actively, grafting is more likely to succeed. Therefore, the rootstock should be selected from robustly growing, well-developed plants; the scion should also be selected from well-developed branches on the outer periphery of the canopy of a robust mother tree.
A. If the rootstock sprouts slightly earlier than the scion, it can promptly supply the nutrients and water needed by the scion, and grafting is likely to succeed;
B. If the scion sprouts slightly earlier than the rootstock, it may die of "starvation" because it cannot obtain water and nutrients supplied by the rootstock;
C. If the scion sprouts too late, the rootstock may exude too much liquid, which may also "drown" the scion.
Some species, such as persimmon and walnut, are rich in tannins, and the cut surface easily forms a tannin oxidation isolation layer that hinders healing;
Pines are rich in resin, and improper handling can also affect healing.
D. The water content of the scion will also affect the success of grafting.
E. If the water content of the scion is too low, the cambium will stop activity and may even die.
Generally, the water content of the scion should be around 50%. Therefore, during transportation and storage, the scion should not be too dry or too wet.
After grafting, attention should also be paid to moisture retention. For example -- when grafting low, soil should be mounded up; when grafting high, moisture-retaining materials should be bound on to prevent water evaporation.
F. In addition, if the cell structure and growth and development speed of the rootstock and scion differ, grafting may produce a "large foot" or "small foot" phenomenon. For example --
Grafting five-needle pine onto black pine; grafting osmanthus onto privet, both will show the "small foot" phenomenon.
Apart from affecting appearance, growth still appears normal.
Therefore, when there is no more ideal rootstock, the above rootstocks can still continue to be used in the cultivation of garden nursery stock.
02. External factors affecting grafting success: These are mainly the effects of temperature and humidity.
Grafting carried out under suitable temperature, humidity, and good aeration conditions is beneficial to healing, survival, and the growth and development of the nursery stock.
01) Temperature: It has a great relationship with the speed of callus tissue formation and grafting survival.
At suitable temperatures, callus tissue forms fastest and survival is easy;
If the temperature is too high or too low, it is not suitable for callus tissue formation.
Generally speaking, grafting is most suitable for plants at around 25°C; but plants at different phenological stages also have different temperature requirements.
Those with earlier phenological stages require lower suitable temperatures than those with later phenological stages. For example, peach and apricot are most suitable at 20-25°C; while camellia is most suitable at 26-30°C.
When carrying out branch grafting in spring, the order of grafting for each tree species is mainly determined by this.
02) Humidity: It has a great influence on grafting survival.
On the one hand, the formation of grafted callus tissue requires certain humidity conditions;
On the other hand, maintaining the vitality of the scion also requires a certain amount of air humidity.
If the atmosphere is dry, it will affect the formation of callus tissue and cause the scion to lose water and dry up.
Soil moisture and groundwater supply are also very important. When grafting, if the soil is dry, irrigation should be carried out first to increase soil moisture.
03) Light: It has a clear inhibitory effect on the formation and growth of callus tissue.
Under dark conditions, callus tissue formation is facilitated. Therefore, after grafting, shading must be provided -- for low grafting, covering with soil both retains moisture and blocks light.
In addition, aeration also has a certain influence on healing and survival. --
Providing certain aeration conditions can satisfy the oxygen needed for respiration by the cambium cells at the union site of the rootstock and scion.
03. Grafting quality: In all grafting operations, the technique and speed of using the knife are the most important.
① Whether the cut surface of the scion is smooth: The key factor for grafting survival is the close union of the cambium of both the scion and the rootstock. This requires that --
The cut surface of the scion must be smooth so that it can fit tightly against the rootstock. If the cut surface of the scion is not smooth, the gap between the scion and rootstock after grafting will be large, more callus tissue will be needed to fill it, and healing will be less likely. Therefore, the knife used to cut the scion must be sharp, and the cut must be made smooth.
② Whether the slope and length of the scion cut surface are appropriate: During grafting, the larger the union surface of the same type of tissue between the scion and rootstock, the easier it is for the conductive tissues of the two to connect, and the higher the survival rate; conversely, the lower the survival rate.
③ Whether the cambium of the scion and rootstock is aligned: In most plants, successful grafting is the result of active division of the cambium of the scion and rootstock. Therefore,
The more accurately the cambium of the two is aligned during grafting, the higher the survival rate.
Fast and skilled grafting can avoid air-drying or oxidative discoloration of the cut surface, thereby increasing the survival rate.
Skilled grafting technique and a sharp grafting knife are the basic conditions for successful grafting.
04. The interrelationships among factors affecting grafting survival: Whether grafting survives is the result of the interaction among various factors. The interrelationships are shown in the figure below:

IV. The mutual influence between rootstock and scion and the selection of rootstock and scion.
01. The mutual influence between rootstock and scion:
01) The influence of the rootstock on the scion: Generally, rootstocks have relatively strong and broad adaptability, such as drought resistance, cold resistance, waterlogging resistance, saline-alkali resistance, and pest and disease resistance, and therefore can increase the resistance of grafted plants. For example:
Using crabapple as the rootstock for apple can increase the apple's drought and waterlogging resistance, and also increase its resistance to chlorosis;
Using Chinese wingnut as the rootstock for walnut can increase the walnut's waterlogging tolerance and barren tolerance.
Some rootstocks can control the size of the plant grown from the scion, making it standard-sized or dwarf.
Rootstocks that can make grafted plants grow vigorously and tall are called "standard rootstocks," such as --
Mountain peach and mountain apricot are "standard rootstocks" for plum blossom and ornamental peach;
On the contrary, some rootstocks can weaken the growth vigor of grafted plants and make the plants short, and are called "dwarfing rootstocks," such as --
Shouxing peach is a dwarfing rootstock for peach and ornamental peach.
Generally, standard rootstocks can delay the flowering and fruiting period of grafted plants and prolong the lifespan of the plant;
Dwarfing rootstocks, on the other hand, can promote earlier flowering and fruiting of grafted plants and shorten the lifespan of the plant.
02) The influence of the scion on the rootstock: After grafting, the growth of the root system of the rootstock depends on the nutrients produced by the scion. Therefore, the scion also has a certain influence on the rootstock. For example -- after birchleaf pear is grafted to become pear, its root system is distributed relatively shallowly and is prone to root suckers.
02. Selection of rootstock and scion:
01) Selection of rootstock: A rootstock with excellent traits is an important part of cultivating fine garden trees. The conditions for selecting a rootstock --
① Strong compatibility with the scion; ② Good influence on the growth and flowering of the scion, and robust growth, high yield, brilliant flowers, and long lifespan;
③ Strong adaptability to the environmental conditions of the cultivation area; ④ Easy to propagate; ⑤ Strong resistance to pests and diseases.
02) Selection of scion: The scion should be selected from adult trees with excellent traits, robust growth; high ornamental value or economic value; and no pests or diseases.

V. Preparatory work for grafting:
Before carrying out grafting activities, preparatory work should be done well in three aspects: tools and supplies, rootstock, and scion.
01. Tools and supplies:
01) Cleaving knife: Used to split the rootstock incision. Its blade is used to split the rootstock, and its wedge part is used to pry open the split opening of the rootstock.
02) Hand saw: Used to saw thicker rootstocks.
03) Pruning shears: Used to cut scions and thinner rootstocks.
04) Budding knife: Used during budding to cut the bud and pry open the budding incision.
The handle of the budding knife has a horn plate, so when using it to pry open the incision, it will not undergo chemical changes with the tannins in the bark.
05) Pencil knife or blade: Used to cut the rootstock and scion of herbaceous plants.
06) Water can and wet cloth: Used to hold and wrap scions.
07) Binding materials: Used to bind the grafting site to prevent water evaporation and to keep the rootstock and scion closely attached. Commonly used binding materials include plastic strips, Chinese iris, cattail, cotton thread, rubber bands, etc.
08) Grafting wax: Used to coat and cover the budding interface to prevent water evaporation and rainwater from entering the interface. Grafting wax comes in solid and liquid forms.
① Solid grafting wax: Its raw materials are 4 parts rosin, 2 parts yellow wax, and 1 part animal oil (or vegetable oil). When preparing, first heat the animal oil until melted, then pour in the rosin and yellow wax, and stir until fully melted. Solid grafting wax usually forms a hard block when cool and needs to be heated and melted when used.
② Liquid grafting wax: Its raw materials are 8 parts rosin, 1 part animal oil, 3 parts alcohol, and 0.5 part turpentine. When preparing, first put the rosin and animal oil into a pot and heat until completely melted, then let it cool slightly, slowly pour in the alcohol and turpentine, and stir to complete. When using, dip a brush to apply it to the interface, and it dries upon exposure to air. Among the above tools and supplies, all kinds of knives and scissors should be ground before useto be very sharp. This has a major relationship with the grafting survival rate and must be taken very seriously.
02. Preparation of the rootstock: When carrying out grafting in general cultivation, the rootstock must be sown 1 year or 2-3 years in advance.
If the rootstock is intended to influence the scion, it must be sown 4-5 years or even 5-6 years in advance, and the specific number of years varies according to the first flowering age of each tree species.
If the scion is intended to influence the rootstock, then the rootstock needs to be young, and sowing 1-2 years in advance is sufficient.
When grafting, if it is planned to cover with soil after grafting, the soil on both sides of the rootstock must be dug open to a depth of 7-10CM in advance.
When budding woody plants, if the soil is dry, irrigation should be carried out the day before to increase the moisture in the tree tissues, making it easier to tear open the bark at the rootstock interface during grafting.

03. Preparation of the scion: Generally, new shoots or one-year-old vegetative branches that are substantial in growth and have plump buds are selected from the middle and upper parts of the outer periphery of the canopy as the scion.
Then the selected scions are gathered into small bundles and marked with variety names.
New shoots collected in summer should immediately have their leaves and the tips of new shoots that are not substantial in growth removed, retaining only the petioles, and should be promptly wrapped in wet cloth to reduce water evaporation from the branches.
If the collected scions cannot be used promptly, the lower part of the branches can be immersed in water, placed in a shady and cool place, and the water changed 1-2 times a day, allowing short-term storage for 4-5 days.
For collecting scion branches for spring branch grafting and budding, it is best to combine this with winter pruning, or they can be collected 1-2 weeks before the trees sprout in spring.
After the collected branches are wrapped, hang them in a well or place them in a cold cellar for sand storage; if they can be stored in a refrigerator or cold storage at a low temperature of about 5°C, that is even better.

VI. Grafting methods:
According to the different materials used, they can be divided into three major categories: branch grafting, bud grafting, and root grafting.
01. Branch grafting method: Mostly used for grafting relatively thick rootstocks, or for changing varieties on large trees.
Branch grafting time: Generally carried out during the dormant period of the tree, especially when the rootstock sap begins to flow in spring and the scion has not yet sprouted.
Advantages of branch grafting: The grafted plants grow quickly, robustly and uniformly, and can become nursery stock in the same year, but a large number of scions is required, and the available grafting time is relatively short.
Branch grafting methods: Commonly used are cut grafting, side grafting, cleft grafting, and bark grafting, etc.
01) Cut grafting method: Generally used for small rootstocks with a diameter of about 2CM, and is one of the most commonly used methods in branch grafting (Figure 5-9).
When grafting, first cut the rootstock at about 5 cm above the ground, then trim the cut surface flat;
Choose the smoother side and use a grafting knife to make a vertical downward cut on one side of the rootstock (slightly into the wood, about 1/5 to 1/4 of the diameter on the cross-section) to a depth of about 2 to 3 cm.
When cutting the scion, keep 2 to 3 complete, plump buds on the scion. Starting from the back side of the bud nearest to the lower cut, use a grafting knife to cut inward to the wood (do not go past the pith), then cut straight down parallel to the bottom. The cut surface should be 2 to 3 cm long, then cut a small bevel of 0.8 to 1 cm at the end on the back side.
Insert the prepared scion into the rootstock cut with the long cut surface facing inward, so that the cambium layers of both sides align and fit closely.
The scion should be inserted to a depth where the upper end of the scion's cut surface is exposed by 0.2 to 0.3 cm, commonly called "white exposure", which favors healing and survival.
If the rootstock cut is too wide, align the cambium on one side, then bind tightly with plastic strips from bottom to top, so that the cambium layers fit closely and the wound retains moisture.
After grafting, to maintain humidity at the joint and prevent water loss and drying, measures such as bagging, soil covering and applying grafting wax can be used. Figure 5-9 Cut grafting

01, Cutting the scion; 02, Making a vertical cut slightly into the wood of the rootstock; 03, Combining rootstock and scion.

02) Cleft grafting: suitable for most deciduous tree species. Usually used when the rootstock is relatively thick and the scion is relatively small (Figure 5-10).
Saw off the rootstock at 5 to 10 cm above the ground, use a cleft grafting knife to split straight down from the center of its cross-section, with the cut about 3 cm long. Cut the scion into a wedge shape, with the cut surface about 3 cm long, and the outer side of the scion slightly thicker than the inner side.
After the scion is cut, pry open the cleft in the rootstock, insert the scion into the cleft with the thick side facing outward and the narrow side facing inward, so that the cambium layers of both align. The upper end of the scion's cut surface should be 0.2 to 0.3 cm above the rootstock cut.
When the rootstock is relatively thick, 2 or 4 scions can be inserted at the same time.
Generally the joint does not need to be tied, but if the rootstock is too thin and the clamping force is insufficient, plastic film strips or hemp rope can be used for binding.
To prevent water loss from the cleft affecting graft survival, after grafting, soil can be mounded over it or grafting wax can be used to seal the opening. Figure 5-10 Cleft grafting images

01, Cutting the scion; 02, Splitting the rootstock; 03, Inserting the scion.

The "cannon twist" graft is a type of cleft grafting. It takes advantage of the fact that Chinese white poplar (Populus tomentosa) does not root easily, while black poplar section species such as Canadian poplar (Populus x canadensis), which have strong compatibility with Chinese white poplar, root easily. Annual branches of Chinese white poplar are used as scions, and annual branches of black poplar section species such as Canadian poplar are used as rootstocks for cleft grafting.
The scion is 8 to 10 cm long with 2 to 3 plump buds, and the rootstock is about 10 cm long. During the idle winter period, cleft grafting is done indoors. After grafting, no binding is done; 50 to 100 pieces are tied into a bundle, stood upright in a pit and stored in sand, and in the following spring they are used for cutting propagation.
03) Bark grafting: this is the easiest to master among branch grafting methods and has the highest survival rate. It is required to be used when the rootstock is relatively thick and the bark peels easily.
Generally, cut off the rootstock at 5 to 8 cm above the ground, trim the cut surface flat, choose a smooth spot, and make a vertical cut in the bark of the rootstock, with a length of 1/2 to 2/3 of the scion length.
Cut the scion into a single bevel 3 to 4 cm long. The cut surface should be flat and straight and extend past the pith, with a thickness of 0.3 to 0.5 cm. At the end on the back side, cut a small bevel of 0.5 to 0.8 cm, or make a slight cut on each of the two sides of the back.
When grafting, insert the scion into the rootstock cut between the wood and the phloem, with the long cut surface facing the wood, and align the back of the scion with the center of the rootstock cut. Pay attention to the upper end of the scion "leaving a white gap”。
If the rootstock is relatively thick or the bark is fairly flexible, the rootstock may also be left uncut, and the prepared scion can be inserted directly into the bark.
Finally, bind with plastic film strips (about 1 cm wide).
This method is also often used for high grafting, such as the grafting of Sophora japonica 'Pendula' and the top grafting and variety conversion of flowering and fruiting trees.
If the rootstock is relatively thick, 3 to 4 scions can be grafted at the same time, evenly distributed, and after survival they can serve as the framework of the new plant (see the figure below) Bark grafting

01, Cutting the scion; 02, Cutting the rootstock; 03, Inserting the scion; 04, Binding.

04) Tongue grafting: tongue grafting is suitable for grafting when the rootstock and scion are 1 to 2 cm thick and are similar in size and thickness.
In tongue grafting, the contact area between rootstock and scion is large, the union is firm, and the survival rate is high. In ornamental nursery stock production, this method is used for both high grafting and low grafting.
Cut the upper end of the rootstock into a 3 cm long cut surface, then at 1/3 from the top of the cut surface downward, cut a vertical slit about 1 cm deep along the rootstock trunk, forming a tongue shape.
On the smooth part of the scion, cut a 3 cm long slanted cut surface accordingly, then at 1/3 from the bottom of the slant upward, likewise cut a vertical slit about 1 cm, corresponding to the vertical slit on the slanted part of the rootstock. Insert the inner tongue (short tongue) of the scion into the vertical slit of the rootstock so that the tongues interlock and are inserted tightly together, then bind (see the figure below).

1, Cutting rootstock and scion; 2, Combining rootstock and scion

05) Bark-tongue grafting: mostly used for tree species in which sap flows and the bark peels easily, but which are not suitable for cleft grafting.
Saw off the rootstock at 5 to 10 cm above the ground, choose a straight, flat part of the rootstock, and shave off the rough old bark to expose the tender bark (phloem).
Cut the scion into a 5 to 7 cm long single-sided horse-ear shape, pinch open the bark layer of the cut surface, gently insert the wood of the scion between the wood and phloem of the rootstock, insert until the scion's cut surface is slightly exposed, then bind (see the figure below).

1, Cutting the rootstock; 2, Cutting the scion; 3, Inserting the scion

06) Side grafting: it is further divided into ordinary side grafting and bark side grafting, and is branch grafting carried out on the side of the rootstock.
It is often used for the propagation of conifers. The rootstock is not headed back, or only the top shoot is cut off, and after survival the rootstock branches above the joint are cut off. Ordinary side grafting: the scion is cut into an offset wedge shape, with the long cut surface about 3 cm long; the cut surface should be flat and gradually slanted, and the back is cut into a short cut surface about 2.5 cm long. The rootstock cut should be made at an appropriate height, choosing a smooth side, with a deep cut from top to bottom; the cut goes into the wood, but the lower end of the cut should not go past the pith, and the cut length should match the long cut surface of the scion. Insert the scion into the cut with the long cut surface facing inward, taking care that the cambium layers align, and bind after grafting to retain moisture. Bark side grafting: in bark side grafting, the rootstock cut does not injure the wood. Make a horizontal cut and then a vertical cut on the rootstock, forming a "T"-shaped cut, with the cut not injuring or only slightly injuring the wood. The long cut surface of the scion is cut flat and slanted, and the two sides of the lower part on the back are each cut once toward the tip, to the extent of exposing white. Pry open the bark and insert the scion, then bind (see the figure below).

1, Cutting the scion (ordinary side grafting); 2, Ordinary side grafting; 3, Cutting the scion (bark side grafting); 4, Bark side grafting

07) Approach grafting: it is a special form of branch grafting.
Approach grafting has a high survival rate and can be carried out during the growing season. However, it requires that both the scion and the rootstock retain root systems, and after healing they are cut apart, making the operation cumbersome.
It is mostly used for ornamental trees and citrus trees in which the compatibility between scion and rootstock is poor and grafting does not easily survive.

Before grafting, bring the scion and rootstock close together. When grafting, bring the two together according to the grafting requirements.
Choose scion and rootstock of comparable thickness, and choose the parts where the two will be approached.
Then bend the scion and rootstock respectively toward the direction of union, each forming a "bow-back" shape.
Use a sharp knife to cut one long oval flat surface on each bow-back, with the cut surface 3 to 5 cm long, and the cutting depth 1/3 of its diameter.
The cut surfaces of the two should be of comparable size, so as to facilitate cambium matching.
After the cut surfaces are made, bring the scion and rootstock tightly together so that the cambium layers of the two cut surfaces align, and bind with plastic strips (see the figure below).
After healing, cut off the lower section of the scion and the upper section of the rootstock respectively, thus forming 1 new plant capable of living independently.

1, Cut surfaces of rootstock and scion; 2, Bound tightly after joining

08) Other branch grafting methods:
A. Bridge grafting:

1, Trimming the wound; 2, Cutting the scion; 3, Binding; 4, Bridge grafting with small seedlings

B. Pith-cambium splice grafting:

1, Cutting the scion; 2, Cutting the rootstock; 3, Condition after grafting; 4, Binding

02, Bud grafting: it is the most widely used grafting method in nursery stock propagation.
It uses plump buds on fully developed current-year vegetative branches as budwood, and is grafted in spring, summer and autumn when the bark peels easily, with autumn being the best.
According to the shape of the bud taken and the way of joining, the specific bud grafting methods include: chip bud grafting, T-shaped bud grafting, square bud grafting, ring bud grafting, etc.
The bud grafting methods more commonly used in nurseries are mainly chip bud grafting and T-shaped bud grafting.
01) Chip bud grafting: also called bud grafting with wood. This method is not limited by the season of whether the tree bark peels, and after grafting the union is firm, which favors survival, and it has already been widely applied in production practice. Chip bud grafting is suitable for large-scale seedling propagation. Its specific method is shown in the figure below.
When cutting the bud plate, cut from top to bottom. At 1 to 1.5 cm above the bud, make a downward cut slightly into the wood, then at 1.5 cm below the bud make a transverse slanted cut, and the bud plate can be removed. Generally the bud plate is 2 to 3 cm long, with variable width depending on the thickness of the scion. The cutting method for the rootstock:
At the selected spot, cut a surface from top to bottom slightly into the wood that is equal in length and width to the bud plate.
Cut away the upper part of this opened bark that slightly includes wood, leaving about 0.5 cm at the lower part.
Then insert the bud plate into the cut so that the cambium layers of the two align, then press the remaining part onto the bud plate, and bind it well with plastic tape.

Chip bud grafting

1, Taking the bud plate; 2, Shape of the bud plate; 3, Inserting the bud plate; 4, Binding

02) T-shaped bud grafting: also called shield bud grafting or "T" shaped bud grafting, and it is the most commonly used bud grafting method in seedling propagation.
For the rootstock, generally 1 to 2 year old small seedlings are chosen. If the rootstock is too large, not only is the bark too thick for easy operation, but also survival after grafting is not easy.
A. Before bud grafting, collect fresh current-year branches as scions, immediately remove the leaf blades and keep the leaf stalks.
B. When cutting the bud plate, first make a transverse cut about 0.5 cm above the bud, with the cut about 0.8 to 1 cm long and reaching deep into the wood;
C. From about 1 cm below the bud plate, cut upward together with the wood to the transverse cut and remove the bud. The bud plate does not carry wood, and the bud is located in the center of the bud plate or slightly above center.
The cutting method for the rootstock: at about 5 cm above the ground, choose a smooth, scar-free spot and make a transverse cut, with the depth based on cutting through the bark;
From the center of the transverse cut, make a vertical cut, so that the cut forms a "T" shape.
Place the bud plate into the cut and insert it downward, so that the upper edge of the bud plate aligns with the transverse cut of the "T"-shaped cut (see the figure below).
Then use plastic tape to wrap the cut tightly from bottom to top, one loop pressing over the previous one, taking care to leave the bud and leaf stalk outside so as to check survival.

T-shaped bud grafting

1, Cutting and removing the bud plate; 2, Shape of the bud plate; 3, Cutting the rootstock; 4, Inserting the bud plate and binding

03) Square bud grafting: also called block bud grafting.
In this method, the contact area between the bud plate and the rootstock cambium is large, and the survival rate is relatively high. It is mostly used for tree species that are harder to survive, such as persimmon and walnut.
Because its operation is relatively complex and its work efficiency is low, it is generally not used for most tree species.
Specific method: take a rectangular bud plate, then cut open the bark on the rootstock according to the size of the bud plate, and insert the bud plate.
The cutting method for the rootstock: one is to cut it into a "]" shape, called "single door" bud grafting; the other is to cut it into an "I" shape, called "double door" bud grafting.
Note: when inserting the bud plate, make sure that at least two sides of the bud plate fit closely with the rootstock cut bark. After inserting, bind with plastic film strips (see the figure below).

Square bud grafting

1, Removing leaves from the scion and cutting the bud; 2, Cutting the rootstock; 3, Inserting the bud plate; 4, Binding; 5, "I"-shaped rootstock

Rootstock cutting and bud plate insertion
04) Ring bud grafting: also called annular bud grafting. Its contact area is large and it survives easily.
It is mainly used for tree species whose bark peels easily, and is carried out after sap flow in spring. Specific method: --
First cut off the scion branch at about 1 cm above the bud;
Then at about 1 cm below the bud, use a knife to make a ring cut deep into the wood;
Gently twist by hand to separate the bark from the wood, and draw out the tubular bud sleeve;
Then choose a rootstock of the same thickness as the bud sleeve, cut off the upper part, and strip the bark in strips;
Immediately slip the bud sleeve onto the wood and align it with the rootstock cut;
Then wrap the bark on the rootstock upward to cover the union between the rootstock and the grafted bud. Bind with plastic film strips (see the figure below).

Ring bud grafting

1, Taking the sleeve-shaped bud plate; 2, Cutting the rootstock bark; 3, Joining; 4, Binding

In addition, in production there are also bud seedling grafting and embryo grafting.

03, Root grafting: using tree roots as rootstock, grafting the scion directly onto the root. Any branch grafting method can be used.
According to the different thicknesses of the scion and the root rootstock, --
it can be grafted upright, that is, cutting the graft opening on the root rootstock;
it can also be grafted inverted, that is, cutting the root rootstock according to the cutting method of the scion, and grafting onto the scion (see the figure below)

1, Upright grafting; 2, Inverted grafting

Seven. Management after grafting:
01, Checking survival, removing binding materials and regrafting:
A. Branch grafting and root grafting: generally 20 to 30 days after grafting, the survival rate can be checked, --
after survival, the buds on the scion are fresh and plump, and may even have already sprouted and grown; if not survived, the scion dries up or turns black and rots.
B. Bud grafting: generally after 7 to 14 days, the survival rate can be checked, --
for those that survive, the leaf stalk falls off at a touch, and the bud body and bud plate are in a fresh state;
for those that do not survive, the bud plate dries up and turns black.
C. During inspection, if the binding material is found to be too tight, it should be loosened or removed, so as not to affect the development and growth of the scion.
Generally, when the new bud grows to 2 to 3 cm, all binding materials can be removed. For fast-growing tree species, branch grafting is best unbound when the new shoot grows to 20 to 30 cm long.
If too early, the joint may still be dried by wind; if the grafting does not survive, timely regrafting should be carried out at a staggered position above or below it.
02, Cutting the rootstock, bud rubbing and sprout removal:
A. After the graft survives, for any rootstock branches still above the joint, the rootstock part above the joint should be cut off in time to promote the growth of the scion.
For most tree species, one-time rootstock cutting can mostly be used, that is--
after the graft survives and before growth begins in spring, cut off the rootstock above the joint, and the cut should be flat to favor healing.
For tree species that are difficult to graft successfully, rootstock cutting can be done in two or more times.
B. After the graft survives, the rootstock often sprouts many tiller buds,
To concentrate nutrients for the growth of new shoots, the sprouts and root suckers on the rootstock should be removed in time, generally 2 to 3 times.
03. Staking:
When the grafted seedling grows new shoots, strong winds can easily break or bend them, thereby affecting survival and normal growth.
Therefore, generally when the new shoot grows to 5-8CM, a stake is placed close to the rootstock, and the new shoot is tied to the stake.
In production, this work is relatively labor-intensive, so other measures such as lowering the graft union, mounding soil at the base of the new shoot, and grafting onto the windward side of the rootstock are usually adopted to prevent or reduce wind breakage. Other tending and management practices are the same as for seedling-propagated plants.

Bougainvillea Large-Scale Rapid Propagation Technology and Cultivation Methods

How to cultivate bougainvillea? Today the editor will analyze this for everyone from several aspects, including the garden uses of bougainvillea, cultivation techniques, and the application of rapid propagation technology in large-scale production of bougainvillea. Let's take a look below!

1 Garden uses of bougainvillea

Bougainvillea is an evergreen flowering shrub or flowering vine, and it has a long flowering period and rich colors. It is used very widely in gardens and can be used as potted flowers or bonsai, can be planted singly, in rows, in groups, or in mass plantings, can serve as the main scenery or as a complementary scenery, can be used in flower beds and flower borders, and can also be used as hedges or ground cover. In garden projects in the five southern provinces and regions, bougainvillea is an excellent garden tree species.

2 Cultivation techniques of bougainvillea

2.1 Bougainvillea is an evergreen shrub. If the temperature is suitable, it remains in growth and development all year round, with no obvious dormant period. However, the most obvious growth period in a year is from late spring to late summer (early April to the end of August). Growth at this time is vegetative growth, that is, growing taller and thicker. If engaged in production during this period, one should seize the time and fertilize timely to make it grow rapidly, even if it forms leggy growth. However, in fertilization, attention should be paid to balancing nitrogen, phosphorus, and potassium, otherwise the leggy branches will be too soft and cannot later be retained for cultivating main branches. In early autumn, as the temperature gradually decreases and sunlight decreases, the growth of bougainvillea also weakens. At this time, for an individual plant, many branches and leaves have already grown. After growth slows, the organic matter produced by photosynthesis accumulates quickly, promoting flower bud differentiation and forming flower buds. Bougainvillea then enters the flowering stage. If it is not being grown as a commercial flower, applying one nitrogen fertilizer at this time (that is, what we often call heavy water and heavy fertilizer) can artificially break its reproductive growth and change it into vegetative growth.

2.2 Bougainvillea is not strict about soil requirements, but it fears waterlogging and is not tolerant of waterlogging. Therefore, a loose, well-drained growing medium must be selected. Generally, a growing medium made of 4 parts humus soil, 4 parts garden soil, and 2 parts sand can be used, or dried pond mud mixed with some coal cinder can be used as potting soil. Current planting substrates can also choose peat, coconut coir plus sand or soil for preparation.

The commonly used propagation methods for bougainvillea are cuttings and air layering, and a small number of varieties can also be propagated by sowing. However, current large-scale production mainly uses cuttings. Bougainvillea roots extremely easily from cuttings. The traditional cutting season is generally from March to June, but based on our years of experience, cuttings taken after flowering have a higher survival rate than those taken before flowering. If cuttings must be taken before flowering, the flower buds on the cuttings must be removed.

2.3 Grasping the cutting season for bougainvillea

According to conventional practice, the general cutting season is suitable from March to June, and in Hangzhou it is from late May to early June. Under natural conditions, bougainvillea cuttings can be taken as long as the temperature can reach 24-30°C and the humidity reaches above 60, and the rooting rate will be very high.

2.4 Care and management after cutting

Light should be suitable: only 40% shade netting can be used. Within 15d, give sparse light, then gradually increase light. New roots grow in 20-30d. After new roots grow, the seedlings should be hardened. In the morning, open the covering shade net and film, cover them again at 11 a.m., and open them again after 16 p.m. After about 7d of this, full sun can be given. During seedling hardening, if the nighttime temperature is lower than 20°C, the shed should be covered at night to prevent freezing.

Moisture retention: within 20d of cutting in a small arched shed, humidity should be maintained above 60. If the weather is dry, pay attention to watering. If cuttings are taken in flower pots, cover with plastic wrap to retain moisture, leaving ventilation holes. In the evening, uncover for ventilation, spray water, then cover again. Now there are better seedling boxes.

Foliar fertilization: spray once about every 10d with 1‰ monopotassium phosphate and 2‰ urea.

Watering: keep the substrate moist in the early stage (air humidity above 50%). After 40d, gradually shift to "alternating dry and wet."

2.5 Transplanting of bougainvillea

The small seedlings that survive 40d after cutting should be hardened for one week under strong sunlight, and given light fertilizer. Divide and pot them at 50-60d. When potting, pay attention to one issue: some varieties do not have very good root systems. In order to prevent soil from falling off during future repotting and transplanting, when potting or bagging, a layer of palm netting or shade netting can first be placed in the container. Also, some varieties have underdeveloped root systems, so adding an appropriate amount of superphosphate when preparing the growing soil is more favorable for rooting.

2.6 Methods to improve the survival rate of bougainvillea cuttings

Some varieties of bougainvillea do not root easily. We can adopt the following methods to promote rooting:

Ring-barking method: about 10d before cutting, make a 1cm ring cut below the node at the base of the cutting branch;

Willow branch extract treatment method: take green willow branches, remove the leaves, cut them into 10cm small sections, soak them in cool boiled water for 5d, and use this extract to treat the cuttings to induce new root growth;

Rooting agent treatment: rooting powder, naphthalene acetic acid, 920, and vitamin B12 can all be used.

2.7 Thick-branch cutting of bougainvillea

The cuttings are 50-100cm long. The upper cut should be sealed with wax to prevent water loss, and attention should be paid to moisture retention. After cutting, buds sprout in 40-60d. After the buds grow to 20cm and the leaves grow stably, pot them. At this time the root system is still not well developed, so branches should be pruned moderately and shade should be provided. To be conservative, all leaves can be removed to facilitate secondary survival. Surviving plants should receive full-light care.

Bougainvillea cuttings first sprout buds and grow branches, and then root. Therefore, when buds sprout and branches grow, transplanting and loosening the soil must not be done, so as not to affect branch rooting. Bougainvillea likes high temperatures and sufficient sunlight. As long as the soil remains moist, it is not afraid of intense sun exposure. In early autumn of the same year, it should be intentionally kept in the pot for one month, that is, after its branches and leaves are lush, water should be reduced, keeping it half dry and half wet, letting its green leaves drop and its flower buds grow vigorously. "Picking leaves can promote sprouting, controlling water can promote flowering" - this is the distinct characteristic of bougainvillea.

Bougainvillea grows rapidly, so during the growth period attention should be paid to shaping and pruning to promote side branch growth and produce more flowering branches. The number of prunings is generally 1-3 times per year (except for shaping), and should not be too many, otherwise it will affect the number of flowering times. After each flowering, remove residual flowers in time to reduce nutrient consumption. After the flowering period, thin out overly dense branches, inner branches, leggy branches, and weak branches. Other branches are generally not pruned, or only the tips are lightly pruned (heavy pruning is not suitable), in order to shorten the next growth period and promote early flowering and repeated flowering.

2.8 Reasonable fertilization

Bougainvillea needs certain nutrients, and appropriate fertilization during the growth period is required to meet its growth needs. Fertilizer should be decomposed, and fertilization should be applied in small amounts many times, with light concentration; otherwise, it is easy to damage the root system and affect growth. Starting in May, apply 10-15% cake fertilizer liquid once every half month to promote spring shoot growth; in the high-temperature season of July-August, to meet its growth needs, apply 10% cake fertilizer liquid and a small amount of superphosphate or a small amount of compound mixed fertilizer liquid once every 15-20d; after September, nitrogen fertilizer should be reduced, and burnt mud ash and a small amount of superphosphate can be applied to promote bougainvillea to bloom in a bright red and beautiful way. To make the flower color more vivid, borax can also be added. When borax is applied as liquid fertilizer, use 6‰; as foliar fertilizer, 2‰ is suitable.

3 Application of rapid propagation technology in large-scale production of bougainvillea

With the development of large-scale production, the traditional propagation techniques of bougainvillea can no longer meet production needs. By using rapid propagation technology, we can produce, within an effective unit area and in a short time, the seedlings needed for production.

3.1 Full-sunlight mist cutting method: carried out in a greenhouse or small arched shed

Seedbed preparation: the length of the seedbed is unlimited. For ease of operation, the most suitable width is 1-1.2m. Leave a 40cm distance between seedbeds. The seedbed should be higher than the ground to facilitate drainage. The bottom of the seedbed should be made arched and drainage holes should be left. Spread a layer of coal cinder at the bottom of the seedbed. After spreading the coal cinder, disinfect with 800-fold carbendazim or chlorothalonil solution. Cover the coal cinder with a layer of geotextile, then spread the prepared substrate, which can be perlite, peat, or coconut coir, with a thickness of 8-10cm.

Install micro-sprinklers in the shed. Determine the number according to the spraying area of the nozzles. Anti-drip valves must be installed on the micro-sprinklers. Install a timer on the water pump switch to regulate timed misting.

Select robust growing branches, cut them into 8-10cm cuttings, and retain 2-3 leaves. After treatment with rooting agent, insert them into the prepared seedbed. The insertion depth is 2cm; it should not be too deep, as deep insertion makes them prone to rot. Turn on the water pump switch and adjust the misting time according to temperature and humidity. The ground temperature must not exceed 30°C, and the temperature should be controlled between 30-32. If the full-sunlight mist cutting method is used, the branches will heal in about one week, root in 10d, and robust bougainvillea seedlings can be cultivated in 15-20d. With the full-sunlight mist cutting method for bougainvillea, rooting time can generally be advanced by about 7-10d. It also has high utilization efficiency per unit area.

3.2 Electric heating hotbed cutting method

Seedbed preparation: the seedbed should be selected inside a greenhouse or small arched shed. Make the seedbed with a bed length within 15m and a width of 1-1.2m. Disinfect with 800-fold carbendazim or chlorothalonil solution. After disinfection, spread a 5cm thick layer of sand. On the sand, lay an electric heating hotbed, with a distance of 8-10cm between heating wires. After the heating wires are laid, cover with another 8-10cm layer of sand. The seedbed is then ready for use. Note here that the heating wires must be fixed and a temperature controller must be added.

In late autumn, select robust 1-2 year old branches, or thicker ones are also acceptable (with 3-4 buds), and cut them into cuttings. The cut surface of the cuttings should be flat. According to the thickness of the branches, tie every 30-50 cuttings into a bundle. Then soak the base in a 1200-fold carbendazim solution with rooting powder added for 1-2h. Take them out and dry them in the shade. Place them in bundles on the prepared seedbed, with the base buried 2cm in the sand. Control the temperature at 28°C. Control the sand moisture at 60%. If it is on the dry side, water with a sprayer; if it is on the wet side, strengthen ventilation. After 7d, callus tissue can form, and roots can grow in 10-12d.

3.3 Tissue culture method

Take bougainvillea buds as explants. After disinfection and sterilization, cut 0.4-2mm sections and inoculate them into MS medium with naphthalene acetic acid added. After 60-70d, adventitious buds grow. Then transfer them to 1/2MS medium. After 15-20d, adventitious roots are induced. When the small seedlings grow to about 5cm, they can be removed from the bottles. Before transplanting, open the culture bottle stopper and harden the seedlings for 2d, wash off the agar from the roots, and transplant them into the prepared substrate. Pay attention to light and temperature-humidity control. After survival, transplant them into containers for normal care and management. The advantages of tissue culture are large production volume, small land occupation, short land occupation time, and the ability to produce virus-free plants.

3.4 ① Application of grafting technology in bougainvillea production; ② Flowering period regulation of bougainvillea (forcing flowering, delaying flowering).

As flowering plants, people all want to regulate the flowering period to meet the needs of our production activities. In fact, many flowering plants can have their flowering period regulated. The plant growth cycle is affected by external conditions such as climate environment, nutrients, photoperiod, and so on. Bougainvillea is a strongly sun-loving short-day plant. The simplest method is light-shading control, which can make it flower earlier. If I want bougainvillea to bloom 50d later, shade it before 9 a.m. and after 17 p.m. With such shading treatment for 25-30 consecutive days, it will definitely bloom 50d later. Note here that when controlling light, if the light duration is less than 9h, growth will weaken and it will not flower.

Water control method: the water control method uses the plant's physiological regulation to adapt to the environment. When plants encounter harsh climatic conditions such as drought, in order to reproduce offspring, they will quickly flower and fruit. Therefore, we can regulate the flowering period of bougainvillea through water control. Water control for flowering can determine the length of water control time according to region, climate, temperature, and variety. Usually, it is suitable when the leaves of the entire plant become wilted. At this time, giving a small amount of water can ensure they do not die of dryness. Continue for 3-7d, then gradually resume watering. During this process, all the plant's leaves will fall off. After buds emerge, apply a thin application of phosphorus-potassium fertilizer. Water still needs to be moderate. Absolutely do not use too much water; too much water will also cause flower buds to turn into leaf buds. For field-grown seedlings, the water control method needs to be repeated several times for a good effect. The water control method should be carried out 40-50d before the desired flowering time. In addition, there is the fertilization control method: adding potassium nitrate during the growth period and spraying monopotassium phosphate on the leaves can both promote earlier flowering. Apply potassium nitrate once every 10d for three consecutive times, and spray 3% monopotassium phosphate on the leaves once every 7d, also for three consecutive times. This method should be carried out 60d before the desired flowering time. In addition, many growth regulators can now force flowering, and they will not be discussed one by one here. If you want to extend the flowering period, the best method is to lower the temperature and control fertilization. Heavy pruning can also extend the flowering period.

The above is all the content on bougainvillea cultivation techniques. Flower farmers who grow bougainvillea can learn more!