POMEWEST NOS

Words Muhammad Asad Ullah and Dario Stefanelli, Research Scientists, Department of Primary Industries and Regional Development

THE Western Australian component of the national NOS project is trialling various apple cultivars × rootstocks × training system combinations to better understand their suitability to 2-D multileader cordon (2 × 2.5 m spacing) system in the Western Australian climate and provide a complete package to growers interested in adopting such systems.

A number of articles on site establishment1 , cultivars and rootstocks2 , and tree training in the first year3 have been published and are available online.

In this article, growth performance of WA NOS trial will be discussed, along with tree training activities being carried out in the second growing season.

Cultivar × Rootstock combinations

Selection of a suitable cultivar × rootstock combination is crucial for establishing an orchard canopy, as well as long-term productivity, viability, profitability and fruit quality. Differences in cultivar × rootstock can become apparent as early as when trees arrive from a nursery as noted in WA NOS trial4 . For example, right out of a nursery, CG.202 had higher whip length and trunk cross-sectional area (TCSA) compared to dwarfing M.26 and M.9 NIC29 rootstocks, irrespective of cultivar type e.g., ANABP 01A , 09, and 14. After tree heading and training of two cordons in the first year, the differential growth trend persisted throughout the 2024–25 growing season.

1 Scalisi, A., Graetz, D., & Zhou, S. (2025). Narrow orchard systems under the microscope. Australian Tree Crop, Dec – Jan edition (pp. 22–23). www.treecrop.com.au/news/narrow-orchard-systems-under-the-microscope

2 Zhou, S., Jacob, S., Scalisi, A., & Stefanelli, D. (2024). Testing narrow row 2D multi-leader apple systems in Western Australia. Australian Fruit Grower, Summer edition (pp. 53–54). https://apal.org.au/testing-narrow-row-2d-multi-leader-apple-systems-in-western-australia/

3 Ullah, M. A., & Stefanelli, D. (2025). WA Narrow Orchard Systems (NOS) project update: Initial tree training (Year 1). WA Grower, Winter edition (pp. 60–63). https://wagrower.vegetableswa.com.au/collections/wa-grower-winter2025/wa-narrow-orchard-systems-nos-project-update-initial-tree-tra

4 Ullah, M. A., Zhou, S. & Stefanelli, D. (2025). WA Narrow Orchard Systems — Rootstock effect on nursery tree size (project update). WA Grower, Autumn edition (pp. 38–39). https://wagrower.vegetableswa.com.au/collections/wa-grower-autumn2025/wa-narrow-orchard-systems-rootstock-effect-on-nursery-tree-size

Cordon lengths and TCSA were measured in June 2025 (end of the 1st growing season). All of the combinations were managed under a similar irrigation and fertiliser regime.

Trees grafted onto semi-vigorous CG.202 showed the strongest performance across cultivars, with ANABP 09A exceeding the target cordon length of 1 metre. In comparison, trees on M.26 showed moderate performance (avg. 0.75 m), whereas M.9 NIC29 rootstock resulted in the lowest growth across the cultivars (avg. 0.62 m).

2nd year tree training

All CG.202 combinations were laid down as cordons by the end of the 1st growing season (Figure 1). However, those on M.26 and M.9 NIC29 were left upright to further grow in the following spring to reach the 1 m target prior to bending.

The topmost terminal bud was selected in winter to extend the shoot and adjacent axillary buds and shoots were removed to minimise competition in early spring (Figures 2a & b). Where the terminal bud grew late in the previous season, a heading cut was made in winter to

FIGURE 1. Trees with ~1 m shoot length were laid down as cordons at the end of 1st growing season (Jun 2025).

FIGURE 2. Minimising competition to enable strong terminal shoot growth by removing competing shoots and buds in spring (a & b) and an example of heading cut to remove a weak terminal bud in winter (c) to stimulate a stronger lateral bud to dominate.

FIGURE 3. Pictorial representation of 2nd year tree training setup in NOS trial site at Manjimup Research Institute.

remove the weak terminal bud and let a strong axillary bud grow and take over (Figure 2c). Heading cuts in winter effectively stimulate lateral bud break so that strong extension growth occurs in the following season from 1-year-old wood. Once the shoots achieved ~1 meter in length, they were laid down as cordons.

The 2nd year tree training also involved vertical leader selection off each cordon to maximise canopy fill. Thus, all the flowers and fruitlets were removed. In our trial, each cordon will have 4 vertical leaders (total 8 per tree), spaced at 25 cm apart. Keeping that in mind, bamboo canes were placed in late winter or early spring to choose appropriately spaced vertical shoots and minimise competition (Figure 3).

Initial selection of shoots was carried out in early to mid-December, when they grew a little over 10 cm. Where possible, leader shoots were selected in-line

FIGURE 4. Summer pruning of laterals on vertical leaders

with bamboo canes and tied using a tapener tying machine. The rest were stubbed back to the cordons.

Emphasis was placed on maximising growth of outer leader shoots because those emerging next to the trunk often become too strong and vigorous, thereby reducing growth of outer leader shoots. A second pass of leader selection was made in late January, to tie leftover leaders to bamboo canes and if there was a need to prune back unwanted vertical shoots.

Growth of vertical leaders was highly dependent on cultivar × rootstock combinations. Since CG.202 is more vigorous than M.26 and M.9 NIC29, it had greater leader length (averaging ~ 0.8 m per vertical shoot by the end of February 2026) across all cultivars. We expect CG.202 to fill 100 % of the canopy space (2 m height from cordon, 2.5 m from ground) by the end of the third growing season. Another distinct feature in CG.202 combinations was its ability to develop lateral growth on the same year leader shoots, particularly on the ones closest to the trunk (Figure 4). These laterals were pruned back to 1–2 nodes to control growth and possibly create spur units for flowering and fruit in the coming seasons.

Additionally, pruning back these laterals would inevitably strengthen the spurs to hold more fruit without the risk of breaking.

Data collection will continue through to the end of the second growing season. In winter, trunk and cordon cross-sectional area, leader final length, leader cross-sectional area, and number of lateral units will also be measured to inform decisions around fruiting strategy for third growing season. Data will be used to compare with other 2-D training systems (e.g., twin leader and Espalier) planted next to NOS training trial, albeit planted a year later.

Acknowledgements

The ‘Narrow Orchard Systems for Future Climates’ project is funded through Hort Innovation Frontiers with co-investment from Agriculture Victoria, NSW Department of Primary Industries and Regional Development, South Australian Research and Development Institute, Department of Primary Industries and Regional Development WA, University of Queensland, New Zealand Institute for Bioeconomy Science Limited, Pomewest, Tobias Industries, and contributions from the Australian Government.