Chikoo/Sapota Grafting, Pruning, and Training:
Today, we are into the discussion of Chikoo/Sapota Grafting Methods, Pruning, and Training procedure.
Introduction to Sapota
Sapota is also called Sapodilla or Chikoo. Some information about Sapota:
- The Sapota is a delicious fruit introduced from tropical America and initially planted at Gholrad near Mumbai in 1898. Its cultivation has spread in Maharashtra, Karnataka and Tamil Nadu. It is evergreen, tropical fruit, spreading habit and lives longer up to 100 years.
- Sapodilla fruit is a rich source of Sugars (13-18%). Sapota pulp contains a sufficient quantity of minerals per 100 grams of pulp. Out of India Sapodilla is cultivated for the extraction of Chicle gum. Sapodilla bark has medicinal value.
- The Sapota when fully ripe is delicious & is eaten as a dessert fruit. The Sapota pulp is sweet and melting. Besides food values, the Sapota fruits are used in some Ayurveda preparations.
- Sapota fruit can be developed in a variety of soils, but deep alluvium, sandy loam, and well-drained medium black soils with pH level 6.0-8.0 are ideal for sapota farming.
- Sapodilla plants are evergreen in nature. The tree canopy has four kinds, viz, erect growing; with drooping branches, spreading branches with sweet fruits & spreading branches with inferior fruits.
- Sapota tree can grow up to 8m high. It has a strong trunk on which scaffolds increase at regular intervals. Fruit bearing is on a new development in axils of leaves. Flowers have six sepals 6 stamens which are petaloid. The Sapota fruit is a berry. The fruit may be seedless or may have 3 to 5 black shining seeds.
- The Sapota is a tropical fruit crop & can be grown from Sea level up to 1200 m. height. It prefers warm and humid weather and grows in both dry & humid areas. The optimum temperature ranges between 12 °C to 36°C.
- Fruits normally mature in about 240 to 270 days after flowering. Fruits at full maturity grow a dull orange or potato color. A mature Sapota fruit when scratched slightly with nail shows a yellow streak instead of the green streak.
Propagation of Sapodilla:
Sapodilla can be propagated through grafting and air layering. Air layering is done in monsoons (July-August). Percentage of success in air layers can be improved by applying 100 to 200ppm of Indole butyric acid solution on the ringed bark before wrapping with moss grass & plastic sheet.
The Sapodilla can be propagated by seeds, by grafting or by layering. However, the commercially followed process is softwood grafting on Rayan seedlings. This method has replaces the earlier process called as an approach grafting. The Sapato, when grafted on rayon, has primarily slow growth, but the tree lasts longer. The layered plants grow vigorously and the process is cheaper as no rootstock is required.
Sapota seeds remain viable for several years if kept dry. The best fruit seeds are large ones from large fruits. They germinate readily but growth is slow and the trees take five to eight years to bear. Since there is great variation in the form, quality & yield of fruits from seedling trees, vegetative propagation has long been considered desirable but has been hampered by the gummy latex. In India, there are several methods are practiced: grafting, inarching, ground-layering & air-layering.
What is grafting?, grafting is a horticultural process whereby tissues of plants are joined so as to maintain their growth together. The upper part of the combined plant is called the scion while the lower part is known as the rootstock. The success of this joining requires that the vascular tissue grows together & such joining is called inosculation.
Plant grafting is a process in which parts of plants are joined together with the ultimate intention of making them unite and continue growing as one plant. A grafted Sapota plant, therefore, is a composite of parts derived from two or more plants. Grafting applies to the dicots and to the gymnosperms because of the presence of a continuous vascular cambium between the xylem & the phloem. But in the monocots that have no vascular cambium, successful grafts are rare & difficult.
Approach grafting must be preferably done at the beginning of the rainy season or during February-March. However, grafting through February-March is more economical as the grafts will have to be maintained in the nursery for a shorter period of time. The success rate of the grafts is high as compared to those obtained in the rainy season.
Different Grafting methods used in Sapota:
The method of soft-wood grafting is similar to that of cleft or wedge grafting. The scion should be a terminal non-flowering shoot of 3 to 4 months maturity with the same thickness as the rootstock. The rootstock of ‘Ryan’ is generally used for soft-wood grafting. The selected scion must be defoliated while on the mother plant at least 7 days before grafting, keeping a part of petiole intact on the selected shoot. Defoliation prior to grafting method helps in swelling of a dormant bud of the scion resulting in greater success. In this grafting method, a wedge-shaped cut is made on the lower part of the scion stick. Similarly, 4 to 6cm long cut is made in the middle portion of the rootstock. The scion stick is then inserted in the cleft of the rootstock & tied with polythene strip. Vigorous sprouting of the scion specifies the successful union of the graft joint. The grafts are maintained in the shade for some time before transferring them in the field.
Side veneer grafting:
Stocks should be 9 to 18 months old, 200 to 400 mm high & with at least 10 pairs of leaves. Scions must be mature terminals, preferably cinctured 30 days previously. Sections of non-terminal wood can be used if the scion branch has been cinctured. The scion is cut to a duration of 60 to 90 mm. A slim veneer of wood some 40 to 50 mm long is cut on the stock to a thickness no more than 1/3rd the diameter of the stock. At the bottom, this cut part is stepped back so as to hold the scion. The scion stick is entirely defoliated & a veneer of identical length to that on the stock cut from the lower half of one side. The surfaces are matched & the scion is bound to the stock with tape. The scion must be completely covered with tape.
After 30 days to 40 days, the tape is removed from the top half of the scion. If the scion is feasible than the stock is cut back to just above the scion. The remainder of the tape is removed after the scion has started to develop away. All rootstock growths should subsequently be removed at regular intervals.
Select stock seedlings from 9 to 18 months old with at least ten pairs of leaves. Scion wood must be semi- to fully-mature terminal shoots (not in an active expansion flush). Best results approach from terminal scions which have been cinctured on the parent tree for at least 30 days. Scions must be cut to approximately 75 to 85 mm long, with all leaves removed except for bottom halves of the top rosette of 6 to 8 leaves. The stock is topped leaving intact at least four pairs of leaves below the graft. Wedge graft with the stock cut set obliquely & the scion cut less on one side than the other. The long cut scion surface faces the thicker surface of the stock. Bind the union with tape & then cover the scion with a polythene bag. The bag must be retained until the scion commences new growth.
It is a commercial technique of propagation practiced over 40 years. The rootstocks in this grafting are raised in pots. The scion remains attached to the parent tree till the union is completed & if the scion branches are high; the stock plants are hanging on the scion tree or placed on a bamboo platform. Inarching performed in the month of December – January and plants are prepared for separation in June – July of next year.
It is essential to resort to inarching when the roots, as well as the trunk, have been girdled. Undamaged suckers, seedlings or rooted cuttings with a stem diameter between 1/4 to 1/2 inch must be used to form the bridge. Trim the wound and cover it with asphalt emulsion tree paint. Space the Sapota plants five to six inches apart around the tree. The grafting can be going when the bark slips on the girdled tree. This will happen around the time the buds swell. Create a smooth, shallow four to six-inch-long cut above the girdled area. Create a short cut on the outside of the stem.
Place the stem against the trunk and create two parallel cuts the width of the scion & the length of the long cut on the scion. Remove the bark exit a ¾ inch flap on the top. Bend the scion into place by slipping the end below the flap. Fasten the flap to the scion with a brad & place two to three brads in the lower portion of the scion. Cover the grafted area with grafting wax or asphalt emulsion tree paint. Rub out sprouts that increase on the scion.
Protect the tree from future damage by creating a cage of ¼ inch hardware cloth (screening). The protective cylinder must be at least one inch away from the bark after it is in place. Two or three inches are preferred to allow for growing room & tree sway. The screen must extend at least three to four inches underground and be 18 to 24 inches high.
Planting a grafted Sapota tree:
For planting sapota plants, pits in the major field must be dug out measuring 60cm*60cm*60cm. The pits should be then exposed to sunlight for a fortnight. The filling of the pits should be done with topsoil mixed with farmyard manure. The pits should be left to settle in the rainwater. At the appropriate time, the plants should be transplanted to the main field. After planting, the soil must be firmly pressed around the base of the plant & light irrigation must be provided. Care must be taken so that the young plants are not exposed to extreme heat & sunlight. A grafted tree produces fruit in three years.
Sapota tree Pruning:
Pruning is normally done during the winter to give shape & reduce the overcrowding of branches. Pruning is important as the flowers & fruits are borne on those branches, which receive maximum air sunlight.
Gardeners often spend hours pruning their trees & shrubs in order to control size and shape, but pruning can do more than dictate a plant’s stature. Regular selective pruning, or maintenance pruning, is a way to keep woody plants healthy and productive. One aim of maintenance pruning is to protect woody plants from pests and disease, which can gain entry into a plant during dead wood, broken branches, and wounds caused by branches that are rubbing together. By thoughtfully cutting back tips, branches, limbs, and stems, encourage youthful growth that produces abundant flowers & fruits as well as to prevent the spread of pests and disease. Knowing where to start with maintenance pruning can seem overwhelming since there are so many different trees & shrubs to consider.
An important gardening method, pruning refers to the trimming & cutting of plants to rid them of an injured, dead, or infected roots and wood. In some cases, pruning is used as a preventive measure to make space for any new seedling or growth. It is important to prune trees & shrubs at the proper time. While some plants require to be pruned after flowering, others are best treated during the winter.
Objectives of Pruning:
- To manage the size of the plant.
- To control the form (structural make up of the plant) this involves number, placement, relative size & angle of branches.
- Improved quality fruits by better light distribution.
- To remove diseased, crisscrossed, dried & broken branches.
- To remove the non-productive parts in order to divert the energy into those parts those are capable of bearing fruits.
- A good proportion of root-shoot ratio.
- Chances of insects-pests, diseases & winter injury are less.
Maximum yield explains Pruning:
Pruning can be carried out to eradicate pests and various types of fungi. Ornamental plants require to be pruned to prevent overgrowth. In landscaping, shrubs & other similar decorative flora need to be pruned directly after flowering. Herbaceous plants, on the other end, require to be pruned after every growing season.
In nurseries, it is a regular practice to prune plants before harvesting or transplanting. This can increase both the quality & quantity of flowers. More delicate flora such as grapevines, fruit trees, roses, and daisies require specialized pruning methods to avoid causing any damage to the plant. Pruning tools include loppers, chainsaws & hand pruners. In some cases, plants can self-prune as an effect of various meteorological conditions such as snowfall. Some flora, such as evergreens, do not need a lot of pruning.
Pruning techniques used in Sapota:
Specific types of pruning may be necessary to keep a mature tree in a healthy, safe, and attractive condition.
- Cleaning is the removal of dead, dying, diseased, weakly attached, and low-vigor branches from the crown of a sapota tree.
- Thinning is the selective branch removal to improve structure & to increase light penetration and air movement through the crown. Proper thinning opens the foliage of a tree, reduces weight on heavy limbs, and helps retain the tree’s normal shape.
- Rising removes the lower branches from a tree to give clearance for buildings, vehicles, pedestrians, and vistas.
- Reduction reduces the size of a tree, often for value line clearance. Reducing a tree’s height or spread is best accomplished by pruning back the leaders & branch terminals to secondary branches that are large enough to assume the terminal. Compared to topping, reduction helps maintain the form & structural integrity of the tree.
Sapota tree Training:
Training fruit trees start when trees are planted, as setting the structure premature helps young trees produce early. It’s more efficient to train trees early by placing limbs in a position, relatively than pruning them later. Growth in fruit trees is regulated by sapota plant hormones. When the buds on the tips of limbs start to produce, auxin is produced. Moves down the limb through gravity, and inhibits the growth of lateral buds below the highest points, an occurrence called apical dominance. The best way to overcome apical dominance is to train branches early to grow more horizontal & remove unwanted upright shoots. The key to producing a well-trained tree in the shortest amount of time is to follow a training plan consistently.
The growth of a strong limb framework is important to allow sapota trees to carry large crops of fruit without limb breakage. If the tree is leggy & lacks lower branches, remove part of the top to induce lateral bud break on the lower trunk. In addition, shoot tip removal (1 to 2 inches) of new shoots of about three feet in length, once or twice between spring and summer will force more branching & make the tree more compact. Any limbs that have a narrow crotch angle must be removed because these may break under heavy fruit loads.
Most trees are trained in the central leader method. A seedling tree produces excellently, giving a shape of an umbrella. However, plants raised through inarching require training for suitable shape. In the beginning, the basal branch helps in developing a thick central system & hence care must be taken to maintain proper distribution of branches on all sides.
In Sapota, new growth and flowering occur simultaneously and it has a mixed kind of bearing habit. Flowers and fruits appear in the leaf axils in the new growth & hence pruning of branches should not be done. Sapota being an evergreen tree requires no regular pruning, but regulation of vegetative growth to develop productivity and quality of fruits is necessary. Dried stems and branches, crowded branches, branches arising in the interior of the canopy & those criss-cross branches should be pruned in June. Rootstock sprouts must be removed regularly. All the growths those come out on the rootstock below the graft joint must be removed.
Training and pruning of young and mature Sapota trees:
The purpose of training and pruning is to keep preferred tree shapes that are capable of the early production of large, high-quality crops with balanced vegetative and reproductive growth.
The development of a strong limb framework is important to allow Sapodilla trees to take large crops of fruit without limb breakage. If the tree is leggy & lacks lower branches, remove part of the top to induce lateral bud break on the lower trunk. In addition, shoot tip removal (1 to 2 inches) of new shoots of about 3 feet in length, once or twice between spring & summer will force more branching and make the tree more compact. Remove any limbs that have a narrow crotch angle because these can break under heavy fruit loads.
As trees mature, most of the pruning is done to control tree height & width and to remove damaged or dead wood. Trees must be kept at a maximum of about 3.7 to 4.6 m (12 to 15 feet). If the canopy becomes too dense, removing some inner branches will help with air circulation & light penetration. Another pruning purpose is to remove dead, damaged, or diseased branches. Low branches must not be cut, however, unless they touch the soil. Cultural practices that are picking, spraying, and pruning is easier on small trees. For mature, large sapota trees in the home landscape that can pose a risk of damaging adjacent trees, we propose a professional arborist provide the pruning services. Make sure the arborist is licensed, has insurance, and knows the local ordinances pertaining to fruit tree pruning in the area.
Read: Fruit Farming.