Canopy Design in Orchards: Improving Fruit Quality and Yield

• Canopy design in orchards achieves a targeted tree form using grafts, pruning, and training.
• Orchards use 3-D canopy designs in low to medium-density orchards.
• 2-D planar canopy designs are used in high-density planting and to facilitate orchard management by machines and robots.
• As tree density increases, fruit quality, and resource use efficiency increase to boost profits per hectare.

Canopy optimization has emerged as a significant factor among preharvest practices to improve fruit quality and increase yields. It can also be investment, time, and labor intensive. Therefore, careful planning is necessary to choose a canopy design, considering the variety, budget, skill, and expertise available. This article provides an introduction to common canopy design systems and their benefits to get you started.

Figure 1: Types of tree canopies, North Sydney Council. (Image credits: https://www.northsydney.nsw.gov.au/trees/planting-trees-guide/3).

Canopy Design

Natural canopy forms are varied: round, oval, spreading, vase, columnar, open, irregular, conical, pyramidal, and palmate. See Figure 1. These natural canopy shapes can be left unpruned in orchards. However, commercial orchards change the canopy form for better management and yield.

Canopy design is a strategy for maintaining good light penetration into the canopy and reducing inter-row spacing and tree size with minimal pruning requirements. Several canopy designs for orchard trees are used, and each provides different benefits and is suitable for specific fruits. For example, cordons and espaliers are ideal for apples and pears, and the fan form is ideal for cherries.

Controlling vigor, using dwarf rootstocks, and pruning and training have made it possible to create new canopy designs, improve light interception and distribution, and increase planting density and production per hectare.

As planting density increases, the complex and deep 3-D canopies with many leaders per tree are replaced by 2-D or flat planar canopies with a single or few leaders in a tree. The different canopy designs used in orchards are discussed below.

Figure 2.: “Canopy architectures of the most widely used training systems in peach and their planting densities. Spacings listed as intra-row × inter-row.” Anthony and Minas 2021. (Image credits: https://doi.org/10.3390/agronomy11101961)

Low-Density Planting

Low-density planting uses standard canopies without training and the open vase canopy.

Open Vase: Open Vase designs are 3-D designs used in low-density plantings of 300-600 trees ha−1. It is used globally for growing peaches. The tree has 3-5 branches secured to scaffolds and produces a denser canopy than the other designs but less yield as density is low. The system requires expertise in training and is time-intensive and costly. See Figure 2.

Medium Density

Several designs are used in medium-density plantings, such as delayed vasette, Quad-V, Hex-V, and palmette. See Figure 2.

Delayed Vasette

The delayed vasette has a similar 3-D canopy architecture to the open vase. Still, it has a central trunk from which four leaders, starting 50 cm above the ground, are attached to scaffolds. After 2-5 years, the canopy structure looks like an open vase. The system is productive and early bearing, and the canopy matures by four years in peaches. It is a practical design for planting densities of 600–800 trees ha−1.

Quad-V

The Quad-V seeks to reduce the initial investment required for V-systems by reducing tree density while maintaining the same leader numbers. Instead of two single primary leaders in the V-system, the quad system has two sets of two primary (or four) leaders. The Quad-V gives the same yield and canopy uniformity as the high-density V-systems in peaches. The spacing is 4.5  x 2.5-3.0 meters to maintain a density of 900–1000 trees ha−1.

Hex-V

The Hex-V systems also aim to reduce tree numbers, and planting density is lower than Quad-V systems, with 750 trees ha−1 planted with a spacing of 3.0 m × 4.5 m. The Hex-V has six leaders trained on three scaffolds. The increased leader numbers distribute rootstock vigor to lower heights to only 2.5 meters, making it manageable without ladders. The system can be used for pears.

Palmette

The palmette system is used in Europe, where spring frosts are expected, and taller trees of 4-5 meters are needed to avoid radiative frost or temperature inversions. There is a central stem with six leaders trained at an angle of 45⁰. It can produce a planar canopy for a fruiting wall but requires machinery or equipment for operations. The planting is done at 2.0–3.5 × 4.0–4.5 m to give 600–900 trees ha−1 densities. It is used for peaches and apples and requires semi-dwarfing rootstocks of low vigor. The system needs expertise and time, so its use is decreasing.

Figure 3. : “Several examples of these intensive and bi-dimensional training systems-the central axis to bi-axis, tri-axis, and multileader. ” Musacchi et al. 2021. ( Image credits: https://doi.org/10.3390/agronomy11091765)

High-Density Planting Systems

High-density planting uses designs that produce narrow planar 2-D canopies with 1.5 × 4.0 m spacing to give densities over 1000 trees ha−1. The height of the trees can vary between 3.0 and 5.5 meters. The canopy designs can be central leaders, Y-shaped, or Cordons.

Spindle or Central Axis

The spindle training system is popular in medium-high-density orchards. It doesn’t require high labor and structure costs. Nursery trees with 4-6 feathers and branches are trained at 40° on trellis or posts.

• In slender spindles, only two permanent whorls of fruits are retained, and further branches are temporary and renewed periodically. The tree reaches 2-3 meters and is used for apples. The fusetto is the Italian version of the slender spindle system.
• In a spindle bush, training creates a cone-shaped tree that reaches 2-3 meters and is supported by wires or posts. One central supports four even-spaced laterals.

Y-System Canopy

The Y-system is also called Bibaum®. In this system, a nursery plant with two preformed axes on semi-dwarfing rootstocks is planted, and the two leaders are trained at an angle of 600 to the row on a trellis. Thus, a year is saved by avoiding heading back to the field and waiting for canopy formation. It creates two fruiting walls with densities of over 1000 trees ha−1. Since leaders are perpendicular to the row, mechanization is difficult.

Various other systems like bi-axis and V-system also use the same principle, with minor differences:

• The tatura trellis developed in Australia is a variant of the Y system and is more productive than the open vase.
• The V-systems have leaders at 15° and usually require a trellis. However, the KAC-V system needs only scaffolds and no trellis; it produces taller trees than the Y-systems.
• The two leaders are trained parallel to the row in bi-axis systems, so mechanization is possible. They give densities of over 2000 trees ha−1

These systems are used for apricots, plums, pears, etc. According to several research findings, the Y or V-systems are the most productive per hectare compared to other canopy designs.

Figure 3.: “Two options of Candelabro system (A, B) and two options of multileader system (C, D) in pear.” Musacchi et al. 2021. (Image credits: https://doi.org/10.3390/agronomy11091765)

Cordons

The trees are grown as single stems and trained to grow at 45⁰ to the ground after the first season for easy harvest. They reach 2.5 meters high, and the planting density is 2.4 × 4.0 m (or 919 trees ha−1). They are used for peaches, plums, and cherries with dwarfing rootstocks. Cordons are the least productive canopy systems but economically better than vase canopies.

Candelabro System

The Candelabro is a cordon system with more than one leader. The aim is to create a planar canopy with vertical and small axes from a horizontal cordon, which requires specialization. It was used between the 16th to 19^th centuries in Europe’s gardens for pears, apples, and peaches. Figure 3. Other multileader systems are also possible. See Figure 3.

Vertical Axis

The vertical axis is used for high-density planting of 2500 trees ha−1 over reduced distances. The trees are trained in a pyramidal shape, intra-row spacings of 30–35 cm, and inter-row spacing of  2.5–2.75 m. The tree has one central axis reaching 3 meters and short branches with periodically renewed spurs. The planting costs are high and need dwarfing rootstocks. Peaches and nectarines use this system.

Espalier

These are established on trellis, walls, or fences. The top three buds are allowed to grow. One is trained vertically, and the others on each side at 45⁰. The top stem is cut, and again, three buds are grown for the next horizontal tier. The system can have up to four tiers to reach 1.8 meters and spaced at 3-4.5 meters. Apples and pears are grown with this system.

Meadow Orchards

Meadow orchards are used for very high-density planting of 0.4–1.0 × 1.3–4.8 m with 3000 to 19000 trees per hectare. Plantings of 2.2 meters-high trees cover an entire field. The field is cropped biennially, with one block harvested while the other that was pruned back regrows its canopy for cropping in the following year.

Evolving Canopy Design

Canopy designs are not modern and have been around for many centuries. Between 1881 and 1945, the orchards in USA switched to shorter grafts that were pruned to give targetted canopy types.

Canopy design for fruits has been evolving constantly, with significant changes starting from around fifty years ago, when the industry moved from multiple leader trees to single leader trees.

Several drivers influenced the evolution of orchard canopy design:

Higher density: Canopies of fruit trees can take several years to reach their target size to provide optimal yield per area. To solve this problem, the planting density was increased and accompanied by pruning and tree training to reach the targeted canopy cover faster in a orchard and prevent overcrowding.

Better light infiltration: Scientific findings in the 1970s showed that fruit quality and yield improved with better light access to fruits and leaves through thinning and pruning.

Making room for tractors: Removing side branches between the rows was necessary with higher density planting and introducing tractors. Since the 2000s, orchards have opted for 2-D systems that produce narrow planar fruit walls to mechanize their operations.

Use of robots: At least in developed countries where the availability of farm labor is decreasing, the use of robots for harvesting fruits like apples or pears is likely to increase. The branch training must produce a uniform and thin canopy for easy access.

Benefits of Canopy Design

Canopy design eliminates continuous and dense foliage. More canopy doesn’t mean more yield or profits. Modern canopy designs have improved profit over traditional low-density planting. However, scientists are still comparing yields between conventional and contemporary canopy designs in high-density plantings to ascertain whether the latter enhances production.

A good canopy design improves profits by providing and ensuring the following benefits:

• 70% more light interception compared to the standard canopy to enhance fruit color, flavor, and sweetness, reducing rejection and food loss.
• Minimizes the energy trees spend to grow structural wood
• Increase leaf area index (LAI) to support more photosynthesis. LAI rises with increasing planting density.
• Canopies are narrower for easy operations management with machines
• The rootstock chosen has low vigor
• Combining canopy design, density, and plant variety provides the targeted canopy coverage within five years.
• Improves air circulations to prevent microclimate that encourages diseases and pests to cut down crop protection costs
• Optimizes nutrition and irrigation use efficiency

The canopy design should be chosen before planting, as this decision influences inter-row and intra-row spacing and the choice of varieties and saplings. After crop establishment, canopy design will determine nutrient addition, irrigation, and crop protection resources and costs, which usually decrease from 3-D to 2-D planar models like V’s, bi-axis, etc.

Measuring Canopy Design Efficiency

LAI is one of the parameters that can be reliably used to measure the efficiency of a canopy design. The LAI increases by avoiding overlapping branches as the canopy becomes open and thin. Devices like the CI-110 Plant Canopy Imager by Bio-Science Inc. can help scientists check the photosynthetically active radiation (PAR) reaching leaves and estimate LAI simultaneously to help further evaluate canopy designs to optimize stone-fruit production.

Sources

Anthony, B.M., & Minas, I.S. (2021). Optimizing Peach Tree Canopy Architecture for Efficient Light Use, Increased Productivity, and Improved Fruit Quality. Agronomy, 11, 1961. https://doi.org/10.3390/agronomy11101961

 

Budhani, A. (2017, Sept, 21). Canopy types and structures with emphasis on geometry of planting. [Dept. of Fruit Science ACHF, NAU]. Retrieved from https://www.slideshare.net/slideshow/canopy-types/80025767#2

 

ISHS Secretariat. (2023, Jan 30). Are 2-D orchard canopy management systems a leap forward or a side-step? Retrieved from https://www.ishs.org/news/hort-forum-are-2-d-orchard-canopy-management-systems-leap-forward-or-side-step

 

Musacchi, S., Iglesias, I., & Neri, D. (2021). Training Systems and Sustainable Orchard Management for European Pear (Pyrus communis L.) in the Mediterranean Area: A Review. Agronomy,11, 1765. https://doi.org/10.3390/agronomy11091765

 

National Park Service. (2022, October 20). Orchard History: Orchard Specialization and Industrialization, 1881-1945. Retrieved from https://www.nps.gov/articles/000/historic-context-orchards-1881-to-1945.htm

 

North Sydney Council. (n.d.) Planting Trees Guide. Retrieved from https://www.northsydney.nsw.gov.au/trees/planting-trees-guide/3

 

Rai, R.K. (n.d.). Canopy management in high density orchards of temperate regions. Retrieved from https://www.slideshare.net/slideshow/canopy-management-in-high-density-orchards-of-temperate-region/251441015#9

 

Stassen, P. J. C., Grove, H. G., & Davie, S. J. (1999). Tree shaping strategies for higher density mango orchards. Journal of Applied Horticulture, 1(1), 1-4.

 

Wilson, R. (2019). Orchard Density and Canopy Design. Retrieved from https://apal.org.au/wp-content/uploads/2019/09/Orchard-Density-and-Canopy-Design-web.pdf