. . . we strive to keep the tree soft with a single dominant trunk and . . . soft bearing units
originating directly on the trunk.
Department of Horticultural Science
University of Stellenbosch
Matieland, South Africa
Deciduous Fruit Grower, January 1997.
recent years.There are a few systems that I feel will have a place in the future, the selection of
which will depend on the growth habit of the variety and the growers’ requirements and
production preferences.The vertical spindle is merely a central leader that has been adapted to
plums at the slightly higher densities being planted at present.For plums I feel that there is still a
future for V-trellis systems with cultivars with a more spreading growth habit.These Vs can be
planted as a) a single row with each tree split into two leaders, one on each side of the trellis, or
b) as a double row with each tree having one leader, planted (unheaded) at an angle and secured
to one side of the trellis.
(11.5 to 13.1 feet) between the rows.This gives densities of 1667 to 2857 trees/ha (675 to
1156 trees/acre).Plantings of single row V-trellis will be spaced from 1.0 to 1.5 m in the row,
while double-row systems are spaced at 0.5 to 0.75 m (1.6 to 2.5 feet) in the row.With either
option there is between 1.0 to 1.5 m between the leaders on each side of the V.Between the row
a 4 m (13.1 feet) spacing is suggested.This gives tree densities of 1667 to 5000 trees/ha (675 to
2024 trees/acre) with the double-row system.
THE TREE
Generally we strive to keep the tree soft with a single dominant trunk and a definite taper to a
soft top.The soft bearing units originating directly on the trunk are not necessarily permanent,
although we do try to keep them as long as possible, at least 4 to 5 years.While the tree lacks a
defined base, a conical form is maintained.
Trees not headed at
planting had a trunk circumference twice that of trees headed at planting.In fact, any pruning in
the vegetative phase of the orchard’s life is dwarfing and delays fruiting.A detailed description
of the unheaded training route is included in this issue (from January 1997Deciduous Fruit
Grower).This method of tree training addresses the particular growth habit of plums.In short,
plums are acrotonic, upright and basal dominant and one must, therefore, pay attention to
correctly manage bud break and subsequent growth.Bending instead of summer pruning is the
preferred manipulation for vegetative growth management.Less pruning and more bending
result in more soft laterals which means more complexity and, thus, earlier production.
PRODUCTION
The performance of an orchard is measured by its production.The following production
estimates are attainable with cultivars like Songold and Laetitia:Year 2 (10 t/ha); Year 3 (25 t/
ha); full bearing (40+ t/ha).
specifications from some of these orchards.The improved size and quality are probably due to
better light distribution within these soft trees.Furthermore, I believe that continued production
of fruit of good size is a function of light distribution and complexity, and the grower has the
ability to manage both of these attributes.From the third leaf onward, we are experiencing
improved picking, thinning and pruning efficiency, probably because of the smaller size and
more labor friendly shape of these trees.
crucial.This not only applies to the bud break manipulations but also bending manipulations.
Our experience has shown that by visiting each tree every week from November to February
(May to October in the northern hemisphere), the total man hours required for bending is
reduced.This is due to the fact that when a shoot is bent at the correct stage the actual
manipulation is not only easier but also more effective in terms of the required effect on tree
form.
BEARING WOOD MANAGEMENT
I believe that bearing wood management in plum high density plantings needs a new approach.
The current system used on our wider plum plantings is based on an annual and fairly rigorous
renewal of bearing wood.In our high density plantings, we do not have the space for too many
1-year-old shoots that can easily aggravate light distribution within the tree structure.We have
recently opted for alternative approaches that rely more on the natural ability of fruiting wood to
maintain vitality provided these fruiting branches are maintained in a more favorable light
environment.We are working with bearing units that are soft and flat, a system very similar to
those used in high density apple plantings in Europe, i.e., the “Lang Snoei”of the Dutch spindle
and the more recent French “fruiting branch”concept.
In plum high density plantings there is no room
for 1-2-3 pruning role.It is the renewal steps 2 and 3 that cause excessive and vigorous shoots.
We prefer to apply the 3:1 ratio rule on previously flattened bearing units so as to diffuse vigor
over the entire bearing unit axis.One still has to remove all upright growing shoots from the
fruiting branch as they tend to become dominant and disrupt the otherwise balanced architecture
of the fruiting branch.Any forks on the fruiting branch should also be removed.Provided the
light distribution within the tree is optimal, it will be necessary to remove/renew only bearing
units, by means of a thinning-out cut, when they become too strong (referred to as “groeitakken”
by the Dutch) or runt out (>50% dieback of spurs).Good light management ensures regular
production and consistent quality via maintained vigor in the bearing units.So far we have had
great success with this method of bearing wood management and are confident that with
judicious pruning and thinning we will be able to maintain fruiting units for up to 5 years and
longer.
manipulations (bending) is done in the first leaf.The trees have a central axis that tapers to a soft
top with soft, precocious bearing units positioned directly on the trunk.Tree vigor is slowed by
higher and earlier production so that the tree maintains a balance between vegetative and
reproductive growth, within the growth habit, on a smaller, more light efficient structure.While
we currently attain this balance of tree architecture on the vigorous Marianna rootstock, we
eagerly await the introduction of more precocious rootstocks.With spacings, I prefer to plant
close enough for the worst site in the block.It is easier to maintain size than to gain size when
the trees are naturally slowing down.Generally within the previously mentioned spacings I plant
Regarding systems, I personally feel that the V is the most efficient from a
light utilization point of view.Economics will determine whether the V-trellis or the vertical
spindle will dominate in the future.
Actual production (t/ha) over the first 4 years for plum high density plantings with
different training and spacing.
________________________________________
Year 2 Year 3 Year 4 Total
Songold
Songold
Songold
Songold
Songold
Spindle
Spindle
V
V
V
4x1
4x1
4x0.5
4x0.5
4x1.5
6
12
5
12
0
—
21
18
30
65
—
—
30
55
—
6
33
53
97
65
Laetitia
Laetitia
Laetitia
Spindle
Spindle
V
4x1
4x1
4x1.5
10
10
0
—
21
55
—
—
—
10
31
55
Sapphire
Spindle
4x1
16
—
—
16
Fruit quality as % Class I and peak fruit size for plum high density plantings with
different training and spacing.
1s tyear
__________________
% Class ISize peak
2n dyear
___________________
% Class ISize peak
Songold
Songold
Spindle
V
4x1
4x1.5
46
94
A
A
—
—
—
—
Laetitia
Laetitia
Spindle
V
4x1
4x1.5
38
77
AA
AA
—
—
—
—
Sapphire
Spindle
4x1
60
A
—
—
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