Tree Training and Pruning Techniques
Training of Fruit Trees
Definition of Training - Training involves cutting away a portion of a plant to provide shape, size, direction of growth, and structure of a fruit tree.
Key practices involved in training include pruning, tying, staking, fastening, and supporting the plants on a trellis.
Benefits of Training
Improvement in Light Interception - Enhances the ability of plants to receive light for optimal growth.
Size Maintenance - Training helps maintain the size of the tree (e.g., dwarfing of trees).
Harvest Efficiency - Improves efficiency in both harvest and spray coverage.
Structural Support - Provides better support for the plants by improving plant frame structure.
Fruit Quality Improvement - Enhances the quality of fruits by improving size and color development while reducing sunscald.
Facilitation of Intercultural Operations - Makes intercultural operations easier and more efficient.
Types of Training
Determined by Goals - Training types depend on goals such as improving plant density, framework, mechanization, intercultural operations, and accommodating climate conditions.
Main Training Types
Central leader system
Open center or vase system
Modified leader system
Multi-leader system
Training on pergola
Espalier
Palmettes
Tatura trellis
Lincoln canopy
Central Leader System
Characteristics
Plants exhibit strong apical dominance.
Overall shape resembles a Christmas tree.
Features rapid, vigorous growth of the central trunk, maintaining undisturbed growth.
Lateral branches are arranged in distinct layers or tiers separated by open spaces, allowing sunlight penetration.
Lower branches tend to be wider and longer.
Branch Structure - Contains 3-4 tiers of branches and 3-4 branches per tier.
Pruning Practices - Pruning occurs during spring and summer, involving bending vigorous, upright shoots at a 45° branch angle to promote lateral growth and reduce vigor.
Examples - Applicable to walnuts, chestnuts, pistachios, persimmons, and figs.
Disadvantages
Can create self-shading or an umbrella effect.
Narrow row spacing complicates the operation of machines.
High initial establishment cost.
Open Center System
Characteristics
Trees develop a bowl or vase shape, with the central leader removed.
The leader of the trees is cut at a height of 1.5 to 2 feet from the soil.
Primary, secondary, and tertiary scaffolds are selected to form a bowl shape, minimizing self-shading.
Examples - Suitable for peaches, plums, nectarines, and apricots.
Disadvantages
Scaffolds formed at the same level can be weaker, risking branch breakage under heavy fruit yield.
Circling strong ropes around branches can provide additional support.
The open structure may expose fruits to sunscald due to high light intensity.
Modified Central Leader
Definition - A hybrid of the open center and central leader training methods.
Training Process
Trees are trained using the central leader system for the first 4-5 years.
After developing several tiers of lateral branches, the central leader is removed.
Characteristics
Also known as the delayed open center system.
Results in trees that are strong and open canopied.
Examples - Applicable to persimmons, apples, pears, and walnuts.
Multi-Leader System
Definition - Involves several leaders, similar to the central leader system.
Advantages
Particularly suitable for varieties susceptible to fire blight; if one leader is infected, it can be removed with minimal loss.
Each leader is maintained similarly to a central leader.
Examples - Applicable to pears.
Espalier System
Growth Characteristics
Two-dimensional growth against a trellis or wall.
Features a vertical stem supporting multiple tiers of horizontal branches (typically four to five tiers spaced 1-1.5 ft apart).
Training Techniques
Young branches are fastened to the trellis before becoming stiff.
Espalier-trained trees require support throughout their life.
Benefits - Enhances fruit production and aesthetics while improving pesticide application and light interception.
Disadvantages - Greater production of water sprouts due to horizontal tying, which can divert energy from fruit production and overall shoot development.
Palmettes
Definition and Characteristics
Similar to the espalier system, resembling an upward-pointing palm.
Branches angle from the central leader at 45° to 60°, with top branches spreading more than lower branches.
Advantages
Minimizes water sprout production, increases productivity, and improves sunlight penetration.
Suitable for moderate and low light areas.
Lateral distance between branches is typically 30 to 40 cm.
Examples - Applicable to apples, pears, and peaches.
Tatura Trellis
Characteristics
Similar to the perpendicular V shape.
Trees are planted closely, and branches are tied to a trellis to facilitate fruit harvesting.
Benefits - Wide angles allow for effective sunlight distribution.
Examples - Applicable to grapes, apples, kiwis, peaches, and pears.
Disadvantages - High establishment and maintenance costs.
Lincoln Canopy
Characteristics
Developed in New Zealand for mechanical harvesting.
Trees are trained on a T-trellis design, allowing shaking to collect fruits below a catching frame.
Disadvantages - Expensive to establish and requires specialized training and pruning techniques.
Dwarf Pyramid
Definition - Resembles the central leader system but with branches starting at 30 to 35 cm above ground.
Characteristics
Size of branches reduces from bottom to top.
Requires extensive pruning to maintain dwarf size.
Genetic Dwarf Trees
Characteristics
Characterized by short internodes and bushy appearance suitable for landscaping.
Naturally have dense canopies, which can lead to self-shading. Pruning and training are employed to open the canopy for better growth.
Examples - Includes varieties like peach, nectarine, and citrus.
Chemical Training
Techniques
Decapitated apple trees treated with 250-1000 ppm IBA lead to wider angle branches.
Morphactins alter plant responses to gravity and light, facilitating growth in any direction.
Auxins suppress lateral branching, whereas cytokinins promote it.
Pruning
Definition - Involves the removal of undesirable parts of a plant (branches, roots, shoots) to achieve specific outcomes:
Desirable yield enhancement.
Improvement of light interception and fruit quality.
Removal of diseased and weaker branches.
Balancing vegetative and reproductive growth.
Elimination of suckers and water sprouts.
Pruning Types and Techniques
Summer Pruning
Conducted during spring or summer to manage vigorous growth, control canopy height/structure, and promote the desired branch architecture.
If performed correctly, less dormant season pruning is required.
Dormant Season Pruning
Conducted when leaves are absent, providing a clear view of the canopy for better pruning decisions.
Ideal for stone fruits (e.g., pruning in Feb to March) as wounds heal faster in late winter compared to early winter, thus preventing infection (e.g., in apricot and grapes, particularly against Eutypa disease).
Branch Pruning - Avoid cutting directly into the branch collar region; instead, cut just outside it to facilitate faster healing and prevent decay.
Classification of Pruning Types Based on Objectives
Frame Pruning - Aimed to provide and maintain the shape of the plant during early growth stages. Involves the removal of weak branches with narrow crotch angles.
Maintenance Pruning - Conducted continuously for perennial plants or annually for deciduous plants. Focuses on removing unproductive shoots, excess branches, and tipping branches for balanced growth.
Renewal Pruning - Severe pruning applied to old orchards or low-yield plants to promote new growth and yield improvement.
Methods of Pruning
Techniques include:
Thinning
Tipping/pinching
Heading back
Skirting
De-blossoming
Thinning
Definition
Involves the removal of shoots from their origin, such as suckers or water sprouts.
Aims to remove unwanted branches, improving sunlight interception and promoting better wind movement to avoid branch breakage.
Indicator for completion: broken sunlight falls on the ground appropriately.
Tipping or Pinching
Purpose
Removes apical dominance, promoting lateral bud growth.
Increases branching, flowering, and fruiting.
Caution - Requires caution, as it can lead to excessive density in the canopy if not managed.
Example - Practiced in elderberry.
Heading Back
Definition
Applied when branches grow vigorously without producing flowers/fruits.
Involves cutting branches back to a few inches of stump with buds to promote new shoot production.
Encourages better flowering and fruiting by removing apical dominance.
Skirting
Purpose
Prevents fruits and leaves from touching the ground to minimize pathogen attacks (e.g., from ants or scales).
Typically entails removing branches up to 50-100 cm above the ground, leaving a clean trunk structure.
De-blossoming
Purpose
Involves removal of excess flowers to enhance fruit quality.
Supports consistent bearing in alternate bearing varieties (e.g., mango, apple).
Effect of Pruning on Plant Health
Lateral Bud Activation
Pruning removes apical dominance, activating lateral bud growth.
Removal of weaker branches with narrow crotch angles enhances overall branch strength and growth orientation.
Dwarfing of Trees
Pruning stimulates new growth as stored energy is redirected for production, reducing overall energy production capacity (i.e., leaf area) in the plant.
Pruned trees tend to be lighter than unpruned counterparts, contributing to a dwarfing effect.
Fruit Bearing
Severe pruning can delay the onset of flowering in plants that produce flowers on one-year-old growth, like cherries.
Removal of branches may eliminate structures necessary for flowering and fruiting.