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Possibilities for multi-leader trees
Article · February 2014
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2. Info
Possibilities for multi-leader trees
Spindles planted at various spacings form
the most common training system in mod-
ern apple orchards. High Density (HD) super
spindles planted at more than 5000 trees
per hectare are extremely productive from
the very first years, and can yield 70 to 90
tonnes per ha by year 4 or 5. Moreover, HD is
an important requirement to achieve mod-
ern fruit walls.
The main drawbacks of traditional HD lay in
the high investment costs and in the difficult
management, that often requires limb bend-
ing, precise crop-load control and skilled prun-
ing. It only takes a small mistake, for instance a
single year of under cropping or bad pruning,
to turn HD super spindles into uncontrollable
trees. This explains why in the last decade, the
dominant position of HD was challenged by
the double-leader training system, which was
proposed by the Mazzoni nursery in Italy. This
cultivation practice is simplified using “Bibaum”
trees, which are a hybrid of the spindle and the
old palmetta. Double budding on M.9 in fact in-
duces a dwarfing effect similar to budding on a
less vigorous rootstock. This is particularly use-
ful when the trees will be grown on fertile soils.
From Bibaum to multi-leader
training
Once the concept of “more than one leader”
was accepted, the next question was whether
the number of leaders could be increased to get
a natural fruit wall from trees grown on fertile
soils and so encourage mechanisation.
A six-year trial of the Adige valley’s main apple
cultivars and extensive practical experience
in the rich soils of the Po Plain, confirmed that
three-leader trees can be created on M.9 from
spindles by allowing two laterals to grow and
removing the competing branches (see Photo
1). Four-leader trees can be created from Bibaum
trees by spreading the original two leaders, two
additional leaders will arise between them (Fig-
ure 1bis). Spindle or Bibaum trees come from
the nursery with several limbs. The develop-
ment of two new leaders from scratch requires
care during the spring and summer of the first
two to three years to keep the leaders vertical
Alberto Dorigoni
Unit Experimental Orchard and Cold Stor-
age, Fondazione Edmund Mach, Italy
alberto.dorigoni@fmach.it
Franco Micheli
Unit Experimental Orchard and Cold Stor-
age, Fondazione Edmund Mach, Italy
franco.micheli@fmach.it
Benefits and
drawbacks
Fertile soils are the
most suitable for
ML trees. The major
drawbacks of the sys-
tem are poor yields
in the first years and
the need to com-
plete tree formation
in the orchard. Once
established, the main
benefits arise from
simplicity in over-
all management. ML
trees are most suita-
ble for single-row hail
nets (also against cod-
ling moth), mechani-
sation of thinning and
pruning and tunnel
sprayers. Increasing
the number of lead-
ers can be a powerful
tool to achieve a fruit
wall in fertile orchards
where spindle would
be unmanageable.
26 36 64 82
22 49 59 77
9 16 21 32
0
50
100
150
200
250
1 leader 2 leaders 3 leaders 4 leaders
n.ofbranches(2-3m)
n.ofbranches(1-2m)
n.ofbranches(0-1m)
Number
of
branches
72 44 38
43 40 39
43 38 28
38 38 23
0
10
20
30
40
50
60
70
80
branch length 0-1 m branch length 1-2 m branch length 2-3 m
1 leader
2 leaders
3 leaders
4 leaders
branch
length
(cm)
Figure 1. Branch numbers at different heights in
the tree (Golden Delicious in year 5)
Fondazione Edmund Mach Fondazione Edmund Mach
Figure 2. Branch length at different heights in the
tree (Golden Delicious in year 5)
EFM 2014-02
18

3. and free of competitive shoots. However, limb
bending, which is important for spindles, is not
needed for Bibaum and Multi-Leader system
(ML) trees. It takes ML trees about five to six
years to achieve a fully formed canopy, one or
two more than the time required for spindles
and Bibaum trees.
The resulting tree shape changes from the coni-
cal shape of the spindle to a rectangular cuboid
of three- and four-leader trees, which look like
fruit walls” (Photo 2). For all of the cultivars tri-
alled, ML trees had many more shoots than the
spindles, particularly in the middle and upper
part (Figure 1) of the tree. The length of the scaf-
fold shoots was inversely related to the number
of leaders (Figure 2). The percentage of branches
longer than 60 cm (important because of the
length of the strings used for flower thinning)
was reduced from 11% for spindles to 5%, 4%
and 3% for two-, three- and four-leader trees
respectively. Consequently, the average width
of the lower part of the trees was dramatically
reduced, in the case of Golden, from 144 cm for
spindles to 76 cm for four-leader trees.
Productivity and quality
Because early yield per ha is a function of tree
density, spindles and two-leader trees planted
at 2900 and 2400 trees/ha respectively were the
most productive systems in the first three to four
years. While spindles reach their maximum yield
around year four, the yield from three- and four-
leader trees, planted at 2200 and 1800 trees/ha
respectively, continues to increase in years five
and six (Table 1). The economic loss of yield in
the early years is partially compensated by the
lower investment. No differences were found in
fruit weight, however, through the years, there
is a greater reduction of red-coloured fruits at
the bottom of spindles than for three- and four-
leader trees (Photos 3, 4 and 5).
Photo 1. When creating three leaders, two
laterals must be grown and competing limbs
removed
Alberto Dorigoni
Photo2. Three- and four-leader
trees look like natural “fruit
walls”. Alberto Dorigoni
A four-leader tree is achieved by sprea-
ding a Bibaum.
Alberto Dorigoni
Cultivars
Weak growing cul-
tivars like Gala tend
to dwarf too much,
while Golden, Rosy
Glow and Fuji are
more suitable for
growing as ML trees.
Once the trees are
fully established, the
benefits are the sim-
plicity in accessing
the canopy and the
overall management,
from pruning through
thinning and harvest-
ing.
Table 1. Yield per ha in the different orchard systems
Gala 2009 2010 2011 2012 2013 2009-2013
1 leader 17 24 49 59 53 201
2 leaders 13 21 41 59 38 171
3 leaders 18 14 45 49 67 192
4 leaders 12 13 39 46 67 177
Golden
1 leader 23 47 68 94 70 302
2 leaders 13 12 66 34 76 202
3 leaders 19 32 83 70 97 300
4 leaders 9 18 55 73 85 241
Fuji
1 leader 16 24 52 77 46 216
2 leaders 25 12 59 64 55 216
3 leaders 22 25 70 38 83 238
4 leaders 18 6 48 33 63 168
Pink Lady
1 leader 25 29 77 75 95 300
2 leaders 17 25 72 78 86 279
3 leaders 26 27 65 97 92 308
4 leaders 12 19 49 84 85 249
Fondazione Edmund Mach
19
EFM 2014-02

4. Pros and cons of ML training
Increasing the number of leaders by splitting
the canopy into two-, three- or four- leader trees
results in significantly weakened trees and a re-
markable change in their architecture. The only
structural wood left is that of the vertical lead-
ers, all the remaining wood is short, does not
bend and is covered in flower buds close to the
trunk. After four years, due to the wide spacing,
ML trees can bear 40-50 kg of excellent qual-
ity apples ( see table 1). Because ML trees have
two to three times as many branches supported
by the same M.9 root system as spindles, the
trees can be headed back or branches can be
removed, they also tolerate short pruning and
mechanical hedging or topping much better
than spindles. This means that the width and
height of the trees can be easily reduced even
more by using Lorette early-summer pruning,
to achieve semi-pedestrian (2.8 m) or fully pe-
destrian (2.3 m) “vineyard-like” orchards.
The main drawbacks of ML concern poor yields
in the first three to four years and the need to
complete tree formation in the field. Given the
lack of the spindle’s central supporting trunk,
special care must be given to two-leader and
ML systems, to ensure that a strong trellis is
able to bear a crop which is uniformly distrib-
uted across the tree and to a large extent hangs
on the support wires. Research must establish
whether, in the end, the low vigour of ML trees
will result in a reduction in fruit weight.
Re-thinking tree spacing
The change in shape resulting from ML training
requires major re-think of tree spacing. Distance
can be reduced to maximise the benefits of
such systems, that mostly profits by alleyways
of less than 3 meters and short “centripetal”
pruning. However, the in-row spacing must be
greater (1.5-1.8 m) to space the leaders about
0.5 m apart. At first glance, ML can be easily mis-
taken for classic super spindles planted at 7000
to 8000 trees/ha, except for the low number of
tree trunks ( see Photo 6).
New techniques
ML is extremely suit-
able for use with new
techniques, such as
single-row hail nets,
mechanisation of
thinning, pruning and
weed management,
or even minimum-
drift tunnel sprayers
and any mechanical
harvesting aids. It is
likely that the thin
canopy resulting from
ML training allows the
fruits to continue to
colour red for more
years than the fruits
on spindles. Finally,
increasing the num-
ber of leaders can be
a powerful tool to
achieve high-density
fruit walls in fertile
orchards where super
spindles would be un-
manageable.
Photo 6. ML can be easily mistaken for classic super
spindles planted at 7000 to 8000 trees/ha.
Alberto Dorigoni
Photo 3, 4 and 5: Red overcolour in the low part of the canopy of Rosy Glow, 2011. Alberto Dorigoni
EFM 2014-02
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