Updated by Bernardita Sallato, WSU, February 2022
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. Information on fruit tree pruning and training systems can be found on this page.
Fruit trees are pruned for a number of reasons including:
- Architecture & size: Fruit trees are pruned to establish the basic tree architecture and to manipulate the tree size.
- Sunlight interception and distribution: Adequate pruning can promote better sunlight distribution and maximize photosynthesis, which is the mechanism for carbohydrates and energy production to support growth and development.
- 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.
- Manipulating vigor: Dormant pruning is an invigorating process that stimulates vegetative growth by diverting the stored energy in a fewer buds.
- Crop load management: Pruning is done to maintain the right balance between vegetative growth, flower production and fruiting. Dormant pruning is a reliable and effective 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.
Summer pruning, considered between rappid shoot growth until the end of the growing season, is a devigorating process that reduces because it involves removing photosynthetic leaf area, thus reducing carbohydrate production.
- Architecture & size: summer pruning can be utilized for training and manipulate the tree size.
- Sunlight interception and distribution: Under vigorous conditions, summer pruning can promote better sunlight distribution and maximize photosynthesis in shaded areas.
- Air circulation: Summer 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).
- Manipulating vigor: Summer pruning is devigorating and can be utilized to control vigor.
- Promote color: Trees can be summer pruned prior to harvest to promote adequate color distribution throughout the canopy.
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.
Root pruning done during the winter or early spring have been used to reduce root volume and control vigor. Many WA growers are utilizing this technique in vigorous apple and cherry orchards. Several factors will influence the effectiveness, such as distance from the tree trunk, depth, if done on one or both sides of the tree, timing as it should aim the period prior to nutrient and carbohydrate removilization, rootstock and soil conditions.
Hand pruning is labor intensive and expensive for growers. Concerns about both labor availability, economic efficiency, and improvement of farm operations have been an incentive for research on mechanical pruning. Several programs around the world 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.
Training fruit trees starts at planting to set the structure of the orchard. Tree growth and fruit development is regulated by plant growth regulators (plant hormones). For example, cytokinins produced in the roots move up to the tree, promoting bud break and cell division. While auxin is produced in the tip of new vegetative growth and moves downward with gravity. The relation of auxins to cytokinins affect vegetative growth. High ratio of auxin:cytokinin will inhibiting bud break leading to apical dominance. Manipulating the branch angle will change this ratio enabling tree training.
Training helps develop a strong tree architecture that can support crop loads, promote precocity and improve the efficiency of many operations, while it could be more costly at the beginning as it is labor intensive.
Free Standings: Semi-dwarf and standard size rootstocks can be trained as freestanding central leader trees, open-center, spanish bush among others. As is, these system are considered to be less productive, less efficient and less precocious, thus outdated.
Trellis trainings: The trees require a trellis systems on a high density planting. Usually they require dwarf or semi-dwarf rootstocks.
Tree Fruit Training Systems by Crop
Bi-axis o multileader (vertical or on a V angle)
Spindle (vertical or on a V angle)
Tatura trellis (vertical or on a V angle)
Vertical Axis (vertical or on a V angle)
Bi-axis or multileader
Central Leader (older)
Sweet Cherry Systems
Kym Green Bush (KGB)
Steep Leader (vertical or on a V angle)
Tall Spindle Axe (vertical or on a V angle)
Tatura trellis (vertical or on a V angle)
Upright Fruiting Offshoots (UFO) (vertical or on a V angle)
Spanish Bush (older)
Super Slender Axe (SSA)
The PNW 667 Cherry Training Systems focuses exclusively on sweet cherry.