There are many possible ways of arranging fruit trees canopies in space.
i. High density planting:
- Early cropping per hectare and the rapid establishment of the canopy has been achieved by high tree densities (1500-5000 trees/ha in different tree fruits, up to 100000/ha in pineapple), planting well feathered (branched) trees and an emphasis on tree training rather than pruning. In order to avoid later problems of excessive vegetative vigour resulting in poor fruit quality, size controlling rootstock have been widely used, with more emphasis on rootstock inducing smaller tree size with higher tree densities.
- Smaller tree canopies are easier to spray, prune and fruits can be picked from the ground.
- As shade is known to be deleterious to fruit quality, smaller tree canopy permit penetration of light in the interior of canopy and thus ensure better fruit quality.
ii. Efficient training systems:
- Important aspects of any training systems include:
1) a rapid achievement of high light interception and early cropping
2) efficient harvesting and
3) the maintenance of good light penetration into the canopy at all times.
- Conical tree shapes, Telephone system (plate 15.6), Tatura trellis (Plate 15.7), V system, Spindles, Kniffen system, etc. ensure better light penetration and interception and therefore production of higher quality fruits.
  Plate 15.6: T-bar (Telephone system) training in kiwifruit Plate 15.7: Tatura trellis system in peach
Some other canopy forms:
Conical trees
- The Dutch have spearheaded the use of intensive systems for apples, with tree densities of 2,000 to 3,300 trees/ha, based on a small conical shaped tree, the slender spindle. Trees are frequently grafted on the dwarfing rootstock M.9, and tree height is restricted to 2-2.2 m.
- All tree management operations pruning, thinning and picking can be done from the ground or with short step ladders.
- The high tree densities ensure a high light interception and the combination of a size controlling rootstock with the conical shape ensures that light can penetrate into the lower parts of the canopy.
- Although use has been made of even higher tree densities and multi-row rather than single row systems, low fruit prices have made some of these very high density systems economically questionable.
- The French axe system has a similar conical tree shape, but is planted at lower tree densities than the Dutch spindle bush and is permitted to grow to 3-4 m tall.
Planar canopies
- To improve light penetration into the tree, the canopy can be trained into a thin layer which, with a suitable wire trellis, can be inclined at different angles to the vertical.
- The Australian Tatura Trellis, originally designed for the mechanical harvesting of peaches, has also been used for apples.
- There have, however, been numerous other forms of V as adopted in pears and Y canopies in peaches (Plate 15.7).
- In some cases individual trees are trained into two halves, in other cases alternate trees down the row are trained to the right and to the left. The horizontal ‘Lincoln canopy’ was also designed for mechanical picking but suffered from excessive annual, vertical shoot growth from the horizontal canopy, with attendant shading of the fruit below. Although such growth could be mechanically pruned off in the summer time, fruit colour was often poor with red skinned cultivars.
- A narrow depth of canopy does not necessarily ensure good light penetration.
Other constraints:
- The soil can impose serious limitations to rootstock choice and similarly the climate can seriously limit the choice of rootstock and cultivar.
- The grower himself is not always seen as a constraint but it is important that the grower has the technical expertise and skill to manage the system; he may not, for example, be able to successfully change from a system he knows well to a new system.
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