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Pruning and Training Systems

Many modern tree fruit orchards are planted high-density using dwarfing rootstocks and training systems designed for maximum sunlight interception, higher fruit yields and quality, and easier worker access. As a result, growers are seeing increased profitability and greater potential for enhanced mechanization of operations. Choosing the correct scion and rootstock combination is essential to ensure that trees will have the appropriate vigor and perform properly for the training methods used. The soil type, irrigation system, tree spacing, and management experience will also contribute to the success of a rootstock and training system combination. Researchers at WSU are conducting trials on new fruit tree training systems and rootstocks, to find advanced, economically feasible ways to grow highly productive trees with excellent fruit quality. Information on fruit tree pruning and training systems can be found on this page.

Pruning

Fruit trees are pruned for a number of reasons including:

  • Architecture & size:  Fruit trees are pruned to establish the basic tree architecture and to limit the tree size.
  • Sunlight interception:  Pruning opens spaces in the tree canopy for sunlight to penetrate and support leaf photosynthesis and the production of carbohydrates and energy that drive the growth of roots, shoots and fruits. Without adequate sunlight penetration during the growing season, flower bud production can be reduced with detrimental affects on cropping in the future.
  • Air circulation:  Pruning can reduce branch crowding, reduce the amount of foliage inside the canopy and enable better air circulation that reduces humidity and allows for better coverage of protectant products (e.g., pesticides).
  • Strength:  Branch angles between a vertical trunk and lateral shoots are stronger as they approach a 90 degree angle. Narrow branch angles are typically weak and they may break under the weight of developing fruit.
  • Control vegetative growth:  Dormant pruning is an invigorating process that stimulates vegetative growth while summer pruning is a devigorating process that reduces growth because it involves removing part of the functional leaf area of the tree.
  • Production:  Pruning is done to maintain the right balance between vegetative growth, flower production and fruiting. Dormant pruning is a reliable crop load management tool.
  • Tree health:  Trees are pruned to prevent the spread of disease or insect damage. This includes the removal and destruction of dead and/or infested wood.

See Guidelines on Pruning ‘Manchurian’ Crabapple for fruit rot control and fact sheet Sterilizing pruning tools: Nuisance or Necessity?

Two regional peer-reviewed publications provide the most comprehensive treatment of the basics of pruning and training fruit trees in the Pacific Northwest. The first, PNW 400 Training and Pruning Your Home Orchard provides recommendations for apple, pear and sweet cherry. The second, PNW 667 Cherry Training Systems focuses exclusively on sweet cherry.

Summer Pruning

Sometimes light pruning is done in the summer to let light into the tree canopy, or to thin branches for training. Timing and amount of shoot removal is important since it can impact carbohydrate supply to developing fruit and also direct sun exposure of fruit that could lead to sunburn. Summer pruning to remove fire blight requires care to make cuts 8-10 inches below the canker and it requires disinfestation of tools between cuts to prevent disease transmission. 

Mechanical Pruning

Hand pruning is labor intensive and expensive for growers. Concerns about both the cost and the future availability of labor have been an incentive for research on mechanical pruning. Tall, narrow tree shapes and tree wall canopies are better suited for mechanical pruning and research programs in the U.S. and Europe are investigating techniques and machines to speed up the process.

At WSU research is being conducted on mechanical pruning of apple and cherry trees. This includes scientists from the Center for Precision and Automated Agricultural Systems. See 3D reconstruction of trees and bushes for mechanical pruning.

A team led by Purdue University and collaborators at Pennsylvania State University has a website related to their research in the area of automated dormant pruning of specialty crops here. This Purdue program was also featured in a 2012 Good Fruit Grower article on Robotic pruning.

Root Pruning

Root pruning is common in Europe to restrict root growth and canopy size in high-density orchards. This type of pruning promotes return bloom and fruit set in the next year. It is most effective when it occurs on both sides of the tree. Dr. Todd Einhorn, Oregon State University, is conducting some root pruning trials in Oregon.

Tree Training

Training fruit trees starts when trees are planted, as setting the structure early helps young trees produce early. Its more efficient to train trees early by placing limbs in a position, rather than pruning them later. Growth in fruit trees is regulated by plant hormones. Cytokinins produced in the roots move up to the highest points in the tree to break dormancy. When the buds on the tips of limbs start to grow, auxin is produced, and moves down the limb through gravity, and inhibits the growth of lateral buds below the highest points, an occurrence known as apical dominance. The best way to overcome apical dominance is to train branches early to grow more horizontal and remove unwanted upright shoots. The key to producing a well trained tree in the shortest amount of time is to follow a training program consistently.

Training Systems

Training helps develop a strong tree architecture that can support crop loads. Training also helps to bring young trees into production early. Basic training systems include:

Central Leader training:  Semi-dwarf and standard size rootstocks can be trained as freestanding central leader trees. A vigorous shoot near the center is chosen at planting time, and competing upright shoots around it are removed. Limbs are spread so as not to compete with the central leader. As is, this system is considered to be outdated. However, many modern systems have their origin from this method.

Open-Center training:  Three or four shoots are chosen to form the main architecture during the first year, and competing limbs are removed. Other systems have developed from this basic tree architectural system.

Espalier training:  The tree structure is created in two dimensions by using trellis systems. The main trunk is tied to the wires. Buds are selected to form branches, and shoots are fastened to training wires. Other styles that built on this method include bush and Palmette systems.

As noted above for pruning, two regional peer-reviewed publications provide the most comprehensive treatment of the basics of training fruit trees in the Pacific Northwest. The first, PNW 400 Training and Pruning Your Home Orchard provides recommendations for apple, pear and sweet cherry. The second, PNW 667 Cherry Training Systems focuses exclusively on sweet cherry.

The 2014 Good Fruit Grower article on Spreading shoots of young apple trees is informative on spreading, bending, and apical dominance in trees.

Tree Fruit Training Systems by Crop

Apple Systems

Bi-axis
Slender spindle
Superspindle/vertical axis
Tatura trellis or V system
Vertical Axis
Central leader (older)

Pear Systems

Bi-axis
Multi-Leader
Central Leader (older)
Slender Spindle (Mostly in Europe)

Sweet Cherry Systems

Kym Green Bush (KGB)
Steep Leader
Tall Spindle Axe
Upright Fruiting Offshoots (UFO)
Vogel Central Leader (older)
Spanish Bush (older)
Super Slender Axe (SSA) – (There is interest in this system, not yet commercialized in the PNW)

Reference:
The seven cherry training systems, R. Lehnert, Good Fruit Grower, May, 2015.

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