Principles of Training and Pruning
The physical techniques that control the size, shape, and direction of plant growth are known as training or in other words training in effect is the orientation of a plant in air through techniques like tying, fastening, staking, supporting over a trellis or pergola in a certain fashion or pruning of some parts.
Principles of training:
- Branches should be spaced at least 15 cm alternately on the main stem and not all at the same place.
- They should be evenly distributed around the stem.
- The branches should not be allowed to grow upwards. Branches should have a medium crotch.
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- To facilitate orchard cultural operations.
- To provide an attractive appearance.
- Lightening to allow air to enter the tree and to expose maximum leaf surface to the sun.
- for increasing production
- for complete colour development
- To protect the tree trunk from sunburn injury.
- To secure a balanced distribution of fruit-bearing parts on the main limbs of the plant.
Methods of Training
The method of plant training is determined by the nature of the plant, climate, purpose of growing, planting method, mechanization, etc. and hence, the wise choice is necessary.
Training in herbaceous annuals and biennials
- These plants are usually grown without changing their growth pattern due to the large number of plants in the area.
- However, plants of some ornamental importance and climbing nature can be pruned in the following ways.
- Staking or supporting plants such as vines.
- Training of vine-type fruit plants or indeterminate types of tomatoes on pergola or trellis.
- Pinching to encourage lateral growth to give a bushier or fulsome appearance to potted plants such as asters, marigolds, and chrysanthemums.
- Removal of lateral buds to form a single stem for larger flowers such as chrysanthemums and dahlias.
- Tying potted chrysanthemums to bamboo sticks and tying different twigs together.
Training of woody perennials
- Woody perennial plants, which remain in one place over wide distances and for a long period, are cultivated to produce quality fruits and develop strong structures for ornamental beauty in different sizes (topiary).
- The following training methods are used in these plants.
- Central Leader system:
- In this system, the main trunk of the tree is allowed to grow freely.
- The first branch is kept at a height of 45 to 50 cm from the ground level and other branches are kept at a distance of 15 to 20 cm on the main stem.
- If the central leader is allowed to grow indefinitely; It will grow more quickly than lateral branches resulting in a strong, robust closed center and tall tree. In such a tree, the fruiting is confined to the top part of the tree.
This system is also called a close centre, because the center of the plant is closed and is also known as a pyramid system because the trained plant looks like a pyramid. This training system is used in the case of some varieties of apple and pear
Merits and demerits:
- The main advantage of this system is the development of a strong crotch.
- Its main disadvantage is the lack of light in the interior of the trees. This weakens the central apex and thus shortens the life of the tree.
- Since the trees are very tall, harvesting and spraying become difficult and costly.
- Lower branches, which remain more or less in shade, eventually become weak and less fruitful.
- Due to the very high size of the plants, there is an increased risk of damage from storms.
- This method of training is not suitable for high-altitude areas and hot dry places where wind velocity is high.
- Open Centre system:
- In this system when the plant reaches a height of 40 to 50 cm. The main stem is then cut off from the top (deheaded).
- From the subsequent vegetative growth, 4-5 branches well-arranged and distributed around the main stem are selected.
- Thus, the trained tree attains less height.
- In this system, the plants take the shape of a bowl.
- This training system is used in plum and peach.
Merits and demerits:
- It helps in transmitting the light to all parts of the tree which is helpful (a) for better color development of the fruit (b) to spread the fruiting area over the entire area of the trees.
- Due to the low height of the trees, there is a facility for pruning, spraying, harvesting, etc.
- Branches form weak and narrow crotch, which can often break due to high stress such as heavy bearing and strong winds.
- It is also possible for the central stem to get sunburned.
- The branches are very close to each other in the same place.
- In this system, the plants take the shape of a “bowl or vase”, which provides a good base for the accumulation of snow. Hence this system is not suitable for high altitude areas where snowfall is common.
Modified Leader system:
- It is intermediate between the above two systems and has advantages of both systems.
- In this system, first, the tree is trained by a central leader system to develop the main trunk without any hindrance for the first four or five years.
- After that, it is cut at a height of 120 to 150 cm from the ground level.
- The first branch on the main stem is kept at a height of 40 cm from the ground and 4 to 5 branches are placed around the main stem at a distance of 15 to 20 cm.
Merits and demerits:
- It results in a small height tree with well-distributed branching, good fruiting due to well-branching distribution, and ease of operation of the orchard due to low height. This system of training is used in fruit plants like citrus, pear, apple
Some special methods of Training
In this system, the height of the plant is kept at 2.0 m. During the first year, the terminal shoot is cut off after the plant has grown to a height of 70 cm. The first branch is left above the height of 25 to 30 cm from the ground. Above this height, all other branches except 3 to 4 branches are removed. In this way, the plants acquire the shape of a bush. The central part of the plant remains open. This system is suitable for apple.
In this system, the plants are pruned in such a way that the lower branches remain long and the upper branches gradually shorten. Alternate tiers of horizontal branches emerging from the main stem scattered around, give the plant a pyramidal appearance. The branches are allowed to grow above the height of 20 cm from the ground level on the main stem. The main stem of the plants and the tip of the branches are cut off to maintain the pyramid shape.
The word espalier is French in origin meaning fence, fruit wall, or pillar. This is a method used especially for the training of apple and pear trees. In this system, three to six tiers of horizontal branches of trees are trained. An attempt is made to develop the lateral branch on the main stem at right angles to each other. Thus, the branches grow parallel to the ground. In this system, wires are tied one above the other in three to six rows using poles. The first row of wire is stretched at a height of 60 to 70 cm, the second row at a height of 130 to 140 cm, and the third row at a height of 200 cm from the ground level. On these wires, the branches of trees are arranged parallel to the ground in both directions. In this system, the line-to-line distance of the plant is kept short as the plants are grown in only two directions along the wire.
Cordon refers to a single-stemmed tree in either a vertical, slanting, or horizontal position, tied to the support of a wire or bamboo cane. This system is generally favorable in apples and pears. These plants produce early fruit compared to the dwarf pyramid and bush systems. Plants are planted at a distance of 1 to 1.5 m. The stem of the plant is tied with wire. Wires are tied over cement and concrete poles that are at 4.5 to 6.0 m intervals. The plant is maintained single-stem by deep pruning of new emergence branches during winter and summer. Depending on the number of main stems stretched to the wire, the system is referred to as a single cordon, double cordon, and triple cordon.
In this system, fruit trees are trained with a trellis of wire for quick and high yield without the use of dwarf rootstocks. The tree is aligned at the center of the trellis and its branches are trained with wire to the trellis. The system was developed by David Chalers, Ban Van De Ende, and Leo Van Heek during the year 1973 at the Irrigation Research Institute, Tatura, Victoria, Australia, the trellis of wire is made using iron poles of 10.5 feet height, on which a 12.5 gauge high tensile iron wire is stretched. A distance of 7 feet is kept between two trellis. The orientation of the trellis is kept in the north-south direction. The tree canopy is maintained in line with the desired frame using mechanical hedgers. Harvesting of fruits is done mechanically. However, the system requires a lot of labor, as it also requires manual pruning and thinning to obtain high yields of large, high-quality fruits. This system gives a higher yield due to maximum light interception and close planting. It is suitable for the training of apple, pear, peach, plum, apricot, nectarine, sweet cherry, kiwifruit, grapefruit, etc.
- Pruning is the removal of unwanted, excess annual growth, dead, dry, and diseased wood from plants.
- It refers to the removal of plant parts such as bud, branch, root, etc. to strike a balance between vegetative growth and production.
- This can also be done to adjust the fruit load on the tree.
- To control the size and shape of the plant.
- In order to make transplanting successful, pruning of leaves/twigs is done to create a balance between root and shoot and less water loss to the plants as compared to the limited root system lost during lifting.
- Improving productivity and quality by regulating crop load and flowering.
- Removal of non-productive vegetative growth such as water sprouts, suckers, dead and diseased wood.
- Knotless timber production in forest trees.
- Thinning the branches so that more light can enter the interior of the tree so that the inner branches also become fruitful.
- Facilitating the shape of the top of the tree to make spraying easier and more cost-effective.
- To regulate the spacing and distribution/direction of branches.
- To prevent the spread of diseases.
Principles of Pruning
- Remove the water sprouts.
- To completely remove a shoot, it must be cut from the base.
- Avoid injury to the bark when pruning. Always, branches of a greater diameter should be cut from the surface below.
- Pruning should be done well before the flowering season.
- In deciduous plants, pruning should be done before winter to reduce the damage caused by low temperatures.
- To avoid diseases, apply Bordeaux paste after pruning.
- Overcrowded, diseased, damaged and insect-infested twigs should be removed.
Plant responses to pruning
Plants’ response to pruning must be well understood in order to successfully achieve the purpose of pruning. Following are some important responses that plants show to pruning.
- Activation of buds: When a branch is cut, the buds below the cut of the branch become active. The bud near the cut is most vigorous and this power decreases in the bud as the distance from the cut increases. This is due to the elimination of the apical dominance of the terminal bud, which triggers the development of lateral buds.
- Dwarfing response: The immediate effect of pruning is undoubtedly the invigoration of new branches due to the diversion of food, but due to the removal of too many leaves, there is a reduction in food formation resulting in stunted root growth which is responsible for the growth of new branches. limits further development. When the growth of new branches is reduced, their length also decreases. Therefore, the net effect of pruning a tree is dwarfed, proportional to the severity of the pruning. Along with the expansion of the top, the spread of the root system is reduced. This also causes dwarfism in the plant.
- Production of water shoots: Intensive pruning often activates dormant buds or adventitious buds and may stimulate buds to develop on older branches. They often produce branches that grow vertically and very vigorously, with long internodes; The angular stems with large, succulent leaves and thorns (as in citrus) are called water shoots or water suckers or bull canes.
- Delay in bearing: When intensive/ severe pruning is done especially in the early years of the fruit plant, fruiting is delayed. Sometimes intensive pruning can also lead to poor yields, as it destroys a great number of foliage and fruiting branches.
Methods of pruning
- Thinning out: When a shoot is completely removed from the base (from the original location) so that no new shoots grow from that spot, it is called thinning out. This thinning is used to remove twigs, water sprouts, etc., growing at unwanted places.
Selective and complete removal of part of the plant is termed thinning.
- Trimming: Trimming the growth of twigs to a pre-determined level, as is done for fences, hedges, and edges.
- Heading back: When branches grow long and vigorously without producing flowers, they are heading back. When a branch is cut almost to the base, leaving a few inches, it is called a heading back. The remaining buds on the stem will give rise to shoots that are important to the tree. These will either be fruiting branches or flower buds to fill gaps in the tree or form vegetative branches that can produce flowers the following year. The shoot of the bud closest to the cut replaces the cut shoot.
- Pollarding: Pollarding is the cutting back of twigs, indiscriminately reducing the height of the tree.
- Girdling (Ringing): In this process, a circular ring-shaped bark of about 3 cm in length is removed. Which accelerates flowering and fruiting by increasing the accumulation of stored food from photosynthesis in the upper part of the plant.
- Nicking: Removing a wedge-shaped piece of bark and making a notch at the bottom of the bud is called nicking. This ensures the accumulation of carbohydrates from the leaves to the bud and can result in fruit bud formation.
- Pinching (tipping): Pinching or tipping is the removal of the tip of a shoot to prevent plant indeterminate growth or to encourage the development of lateral buds. This is done in marigold and chilli at the time of transplanting.
- Disbudding (nipping or rubbing): Nipping or robbing young buds to inhibit their growth. They are removed when the buds appear in the wrong places. Similarly, the sprouts (buds) on the rootstock are also disbudded.
- De-blossoming: Removal of surplus flowers from the tree to produce fruit regularly year after year is called de-blossoming. It is used in alternate bearer trees like mango, apple, etc.
Seasons of pruning
- It depends on the type of branch, type of plant species, and time of bud formation.
- Water sprouts can be removed at any time of the year, along with removing diseased, dead, and dry wood.
- Pruning of healthy branches should not be done when trees are flowering or bearing fruit, as the resulting disturbance destroys flowers or fruits.
- In deciduous trees, pruning can be done before the end of dormancy.
- In evergreen plants, pruning should be done before the start of active growth or post-harvest.
- Summer pruning of deciduous trees and pruning of evergreens during the active growing season also delays the formation of flower buds by prolonging the time of vegetative growth.
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2.Jitendra Singh Basic Horticulture (2011) Kalyani Publications, New Delhi
3.K.V.Peter Basics Horticulture (2009) New India Publishing Agency
4. Jitendra Singh Fundamentals of Horticulture, Kalyani Publications, New Delhi