Hedging and topping
With increased plant density and hedgerow plantings, machine pruning becomes more necessary to save time. This is usually when trees are too high to harvest easily and grow too wide into the row to access.
There will always be some crop loss from hedging. The benefits of improved access and increased fruit size have to be weighed against the crop loss and the cost of the operation. Hedge and top only as much as necessary.
- restored inter-row access (hedging)
- reduced tree height (topping)
- trees can be re-invigorated
- fast operation - can be done quickly.
Side hedging can be done at an angle of 15° to 25° from the vertical to allow better light penetration to the lower parts of the canopy. Trees can be hedged at 25° to form a triangle shape and then flat-topped (Figure 1).
If side-hedging at 15° from the vertical, trees also need to be topped from both sides at 30° from the horizontal to allow light penetration to lower parts of the canopy (Figure 1).
Figure 1 Two styles of side-hedging and flat-topping
Machine pruning can be carried out over a three-year period. Prune one side in one year, the other side the following year, and the top the year after. This reduces crop losses in any single year.
Alternatively, hedging of entire trees can be carried out in one year, on every second row. Some growers carry out side hedging and topping on the entire block in the on-crop year and skirt pruning in the off-crop year. It is important to begin machine pruning in good time, otherwise, the cuts will be too large and crop losses too high.
Regrowth management resulting from pruning is vital if the full benefits are to be achieved. It is ideal to do this several months after pruning in late summer to mid-autumn, when regrowth is about 30cm long.
Healthy trees will produce localised shoot growth around the site of large cuts after pruning, as well as general regrowth through the canopy as a result of increased light intensity.
Watershoots coming from low down on the trunk or main scaffold limbs should, in most cases, be removed entirely (see Figure 2 below). Other excess shoots can be thinned by hand, and spaced to about a hand span apart. Both topping and hedging force regrowth shoots to branch.