Reducing Canopy Size

There are a number of ways to control the size of your tree's which could be undertaken, even in normal seasons. Drought conditions may encourage you to consider undertaking summer pruning and RDI. The latter has already been covered quite extensively on this website, so this article will concentrate on summer pruning. In general the most efficient way to reduce vegatitive growth on fruit trees is by careful irrigation management. However there are a number of reasons you could experiance excessive vegitative growth in the form of rapidly growing water shoots.

Stone fruit trees of various ages in a Woorinen orchard.

A light or crop will encourage the tree to grow vegatively. You may have had small fruit last year as a result of dry sub-soils and interows under trickle irrigation. That scenario will undoubtadbly encourage you to thin harder this year to maintain size. If there is not a corresponding change in water management or summer rains are experianced trees will grow with excessive vigour. Like wise, if you have removed fruit alltogether to maintian trees until the end of the drought, careful management of vegetation and soil moisture managment will be needed.

Apples:
Summer pruning can be used to reduce excess vegetative growth caused by fruit removal on apples. Care must be taken not to cause further stress by excessive pruning. The timing of summer pruning is important. It is better to wait until the terminal shoots have stopped growing before you prune.

(Source: Julie Brien, District Horticulturist, NSW Agriculture, Tumut)

Stonefruit
There is a direct link between canopy size and tree water use. Although, radical removal of limbs (Eg. reducing the number of leaders/tree) should only be attempted after fully considering the implications to future yeilds. Removing entire limbs will effect yeild for a number of years. Other losses in effiency may also be experianced while the tree structure is regianed.

Summer pruning is the action of removing shoots from the interior, shortening spurs and a general shaping of the tree for maximum light interception. Summer pruning is recomeded as best management practice. The effect of summer pruning on tree water use are untested and according to a Department of Primary Industries scientist probably negliable.

Less radical machine pruning to reduce tree hieght by up to 30cm could be undertaken during the dormant period. How ever any reduction in tree size will spur the tree into growing more vegetation. Therefore a corresponding water management regime must be carried out. That regime will involve careful monitoring of soil moisture and RDI.

(Source: DPI)

Citrus
Tree water use is directly related to canopy size, so reducing the canopy reduces water use. Figure 3 illustrates the impact of canopy size on monthly irrigation applications to navel orange trees. The amount of tree canopy you remove for each block should be based on tree age, crop load, stage of growth, long-term block viability and how much water needs to be saved. Providing trees are given sufficient levels of water and nutrients they should recover to form a vigorous canopy that produces good quality fruit.

• Skeletonising: Skeletonising is the most severe form of canopy reduction, involving the removal of nearly all tree branches and foliage. This type of pruning is normally used to rejuvenate old trees. Trees that have been skeletonised will use a lot less water, but can take between 2-3 years to come back into full production.
  

• Hedging: The best time to hedge trees is in late winter/early spring to reduce the risk of sunburn to the newly exposed limbs. A light hedging will not significantly impact on next season’s production, however a medium or heavy hedging can result in trees being out of production for 1-2 seasons. One option is to hedge only one side of the tree to reduce the impact on yield.
  

• Pruning for regrafting: Cutting back trees for grafting will also reduce water use.