Branchless multi-leader trees open new windows for more efficient production, due to lower cost per unit of fruit, and/or higher price that the orchardist receives per unit of fruit.
Orchardists and researchers know that trees (especially apples) that are closely planted and arranged so that they intercept optimum sunlight, improve productivity and keep costs in check.
Should canopies be vertical or angled?
Both have merits. Orchardists usually decide according to locality, crop, experience, quality of labour available, advice from progressive orchardists and researchers, and whether the system could be mechanised.
There are many systems that orchardists could use successfully. However, there is room for improving the ‘bottom line’ with a modified system.
One way is to use multi-leader trees, advocated by orchardists and researchers in several countries.
Features of branchless multi-leader trees include:
- The architecture of the tree is simple with only a primary structure of a short trunk with two or more leaders per tree that are dressed with short fruiting wood.
- Branches are neither created nor manipulated.
- The trees are closely-planted and supported by a trellis to form canopies that are either vertical or angled.
- The branchless leaders are neither basitonic nor acritonic.
- The thin two-dimensional canopy is uniformly filled with leaders. There are no gaps in the upper part of the canopy.
- The system is easily mechanised.
- At first, the roots are not restricted and push the trees to fill their spaces on the trellis as quickly as possible (short vegetative phase). Later, when roots have filled their space and are then restricted, they help to control vigour of the leaders.
- Vigour is equally divided over four leaders, and more easily controlled than with trees with two leaders. The rootstock controls vigour less.
- The crop can be accurately targeted, monitored and managed, because all four leaders have the same numbers of fruit. During winter, bud counts help to determine the intensity of pruning needed to establish the crop load for the coming season.
- Unskilled labour can easily learn to prune the trees and to thin and harvest the fruit.
- Some leaders can be used as pollinisers; this improves the pollination strength, and individual polliniser trees are not needed.
- The thin canopies improve air circulation, allow good spray coverage, reduce spray drift, and need less spray material per hectare.
- Leaders can be renewed when they become less productive. One leader is removed at a time and is replaced by a new leader.
- Nursery trees do not need to be costly, double-budded or the method patented.
- Multi-leader trees preferably start in the nursery when they are headed to force sylleptic branching. After the trees have been planted in the orchard, suitable forks are selected and cut back. The trees then generate several shoots out of their heads. Four shoots are then gradually selected to make sure that the future leaders are uniform in size and thickness.
- After they are planted, nursery trees are headed, which helps prevent transplant shock.
Continued next month
For more information, see Tree Fruit August 2014
