Info

The fruit wall: are tall trees really necessary?

A large number of canopy shapes and planting con�gurations are used in fruit growing

worldwide. In the past, but even today, in China for instance, tree canopies were made up

by complex structures, with 3 levels of organization, starting from the main stem up to

big branches, minor branches and bearing wood. Even in modern orchards based on conic

shaped systems there is a robust secondary structure in “centrifugal pruning” with the aim

of having productive wood and crop in the periphery (Figure 1). The height and width of

trees has not only a major in!uence on production and quality, but also on many cultural

practices and on crop protection.

Many fruit growers and consultants are con-

vinced of the advantages of tall trees, especially

in fruit-growing areas of South Tyrol, Italy, where,

they claim, the expensive land is better exploited

by tall trees. However, if we take into account

the additional costs and di!culties of produc-

ing apples in the top of the tree, the situation

changes. Working platforms are expensive and

picking from ladders is slow and risky. There is a

relationship between tree height and between-

row spacing, which in turn is a function of tree

canopy width, and the machines available on the

farm (tractors, mowers, etc.). Assuming that grow-

ers can manages to keep trees short and slender,

the question remains how much can the height

of the tree be reduced without this negatively

a"ecting light interception and consequently,

yields. The 1.5 metres clear alley required for the

machinery can in modern orchards be achieved

using very di"erent systems. For instance, fruit

walls can achieve the same production volume

(for example, 80 tonnes per hectare) by chang-

Tree shapeMechanical pruning is

an important tech-nique when creating a fruit wall. Machines

work quickly, whether or not the trees have

leaves. They also con-sistently prune the

tree into the correct shape. In addition,

pruning machines are #exible to deploy and they can be used the

year round, also in periods when there is

a limited amount of labour available.

Alberto DorigoniFondazione Edmund Mach

Center for Technological Transfer, Italy

alberto.dorigoni@fmach.it

Franco MicheliFondazione Edmund Mach

Center for Technological Transfer, Italy

50cm 100cm 150cm 200cm

Figure 1: ‘Centrifugal e"ect’ of long pruning (Chile).

Alberto Dorigoni

EFM 2015-0610

ing the parameters of the planting system from

a few rows of large, tall trees to many rows of

low, narrow fruit walls (Figure 2).

Advantages of short trees

The advantages of short and thin fruit walls con-

cern management, cultivation characteristics and

environmental aspects. With small pedestrian

size trees, no work platforms or ladders are re-

quired, which is safer for the workers. All horchard

management operations, from pruning through

thinning to harvesting, can be done faster and

easier from the ground. Picking aids can be em-

ployed more e!ciently. The quality of the fruit is

more homogenous, because there is less di"er-

ence between inside and outside of the canopy.

Moreover, every form of mechanisation is easier

for a low fruit wall than for standard trees. Con-

sider for instance the use of #ower thinning ma-

chines, pruning, tunnel sprayers, weed control,

etc. The lower support system required for short

trees is easier to install and the posts do not need

to be joined together transversely. It is also easier

to protect the trees with multifunctional nets

from codling moths and hail. Such nets can also

be used to thin some varieties by closing them

around the trees during full bloom. In fact nets

can be used at bloom time to physically hinder

bee activity and reduce the available light result-

ing in more fruit abscission.

Disadvantages of low trees

Because there are 50% more rows of low fruit

walls than with standard systems, crop protection

takes more (driving) time. The additional driving

time is in part compensated by the higher driv-

ing speed. The reintroduction of the two-row

planting system can be an alternative. Orchard

Regulating growthThere are of course many supplementary measures that can be used to regulate growth and that can help to keep the fruit wall low and nar-row. These include root pruning, the use of chemical plant growth regulators and controlled water stress.

Figure 2: At a between-row distance of 2.80 metres, there is a gap available between the fruit walls

of 2.00 metres for the machines. In 2014, this ‘multi-leader’ Golden Delicious orchard in South Tyrol

achieved a production of 87 tonnes per hectare (53 kg/tree x 1.650 trees/ha).

Alberto Dorigoni

2.0m

2.7m

2.8m

0.4m 0.4m

bearing

wood

Figure 3: Golden Delicious on the MM106 rootstock becomes surprisingly

dwarfed when these trees are cultivated as multi-leader trees with six le-

aders instead of a spindle. These trees with six leaders are 2.50 metres tall.

2.3 m

Alberto Dorigoni

11EFM 2015-06

Fig: Cultural practices improved by fruiting wall

– Hand pruning

– Hand thinning

– No limb bending

– Branch renewal

– Harvest

– Mech. harvest aids

Mechanical thinning

Mechanical pruning

Mech. weed control

Less PGR’s

Less spraying volume

Faster leaf drying

Reduced drift

Tunnel sprayers

Multi-task nets

SSCD

FRUITING WALL

MANAGEMENT

ADVANTAGES

(Economic

sustainability)

ADVANTAGES IN

MECHANIZATION

(Ecological

sustainabilty)

AGRONOMIC

ADVANTAGES

Light interception / penetration

(no distinction between

inside and outside)

life may be diminished by the tendency of trees

to grow upwards and lose quality in the lower

portions of the canopy. However, using the cor-

rect cultivation techniques, it is possible to keep

a good balance between vegetative growth and

cropping and to overcome the disadvantages

mentioned.

Techniques used to form fruit walls and to keep them in shape

Even though genetic characteristics unargu-

ably determine vigour, the shape and size of

fruit trees is mainly determined by external fac-

tors. This means that cultivation techniques can

be employed to create very di!erent canopies

on genetically identical trees. There are various

ways to “de-structure” tree canopies and get rid

of large branches.

Increasing the number of leaders

Double leader-trees and ‘multi-leader’ (ML) trees

have a natural tendency to form a narrow and

dense hedge with little or no secondary struc-

ture. This is because the vigour is distributed

over more than one leader as the only struc-

tural wood. Since, as far as vigour is concerned,

increasing the number of leaders has the same

e!ect as using a more dwar"ng rootstock, the

EFM 2015-0612

Various advantagesThe objective to im-prove the economics and ecologic aspects of the fruit industry can be accomplished by just changing the tree shape. From the crop protection viewpoint, the fruit wall also has advan-tages. Thanks to the low and narrow tree canopy, the distribu-tion of crop protec-tion products is good throughout the year. Various machines and techniques that are common in wine pro-duction can be used in modern orchards consisting of fruit walls in a new scenar-io of orchard param-eters that involve tree height, spacing, ma-chinery, etc.. People from outside of agri-culture, including the tourist industry, can also bene�t from the lower input of chemi-cals and the reduced drift associated with low fruit walls.

2011 cut

2012 cut

New shoots

and

buds

10cm 20cm 30cm 40cm

Hand pruning

“Lorette”

Crown of 4

new leaves

Stalk of the

old leaf

Distance from the trunk

Figure 4: Golden Delicious Bibaum: Several consecutive years of summer

pruning have promoted the growth of productive shoots close to the trunk.

Figure 5: The strong “de-structuring” e�ect of summer pruning on a vigorous branch of the Empire

apple variety. This variety normally grows long branches.

Alberto Dorigoni

Alberto Dorigoni

1-year old wood produce new spurs between the

cut and the tree trunk (Figure 4). ‘Lorette’ prun-

ing, and other forms of non-dormant pruning,

helps to remove old, structural wood and to turn

it back into bearing wood. The e�ect is so strong

that some varieties including Empire lose their

natural centrifugal growth habit (Figure 5). Prun-

ing after harvest, compared to winter pruning,

is also an interesting measure to reduce vigour.

number of leaders is an additional variable that

can be used when determining the correct sys-

tem in new orchards.

Trees with multiple leaders are positively assessed

throughout the world. Started in Italy, where the

Mazzoni tree nursery has patented trees with two

leaders as ‘Bibaum’, the growing system with two

leaders was implemented in particular in Spain

and the United Kingdom, but also in the rest of

Western and Eastern Europe. The !rst orchards

of multi-leader trees have also been planted

in Chile, the United States, Australia and New

Zealand. The width and height of multi-leader

trees can be controlled much better than spin-

dle-shaped trees. This applies even for trees on

vigorous rootstocks (Figure 3).

Short pruning in summer

While long pruning and thinning of strong

branches is recommended if centrifugal growth

of the tree is desired, any shortening of branches

tends to bring back bearing wood near the trunk.

Of course, such short pruning, when not accom-

panied by the correct strategy, can cause pow-

erful regrowth, in particular if it is performed in

winter. At the beginning of the 20th century, the

Frenchman Louis Lorette demonstrated that the

growth of vigorous apple and pear trees could be

tempered by repeated manually pruning trees in

summer. Similar e�ect can be achieved by me-

chanical pruning in summer. The ‘de-structuring’

principle is simple: summer pruning performed

early directs the "ow of sap to the fruits and buds

instead of to the shoots. A few months later, the

terminal stipulary eyes at the base of the leaf on

13EFM 2015-06