Acta Horticulturae

A Traditional
Cordon Espalliar Step Over Double U
B Spindles
Conference pear
Training systems: A. Traditional; B. Spindles; C. Trellis.
When considering apples, pears, plums and
sweet cherries, which flower and crop mainly
on spur structures (rather than on fruit buds
formed as terminal buds on short shoots or in
the leaf axils of one-year-old wood), severe pruning,
by making heading cuts to remove half to
two thirds of shoot lengths, should be avoided
in almost all cases, since it results in severe
reductions in yields in the subsequent few seasons.
If any severe pruning is practiced whole
shoots should be removed to their base and
other shoots left intact or only lightly tipped. If
severe dormant season pruning is the only
method of restructuring old neglected trees,
then it should be supplemented by root pruning.
The combined shoot and root pruning
treatments will help avoid the rapid regrowth of
new shoots.
Pruning shoots in the summer has only limited
effects on tree vigour of most crops and may
result in loss of spur production on some cultivars.
In many countries experiencing low light
levels, summer pruning is used only for opening
up the tree canopy, so as to facilitate the distribution
of light and improve fruit colouring. In
areas experiencing hotter summers the technique
can have negative effects by increasing
problems such as sunburn.
Branch bending is a far better method than pruning
for reducing shoot vigour. The speed of
Sunburst sweet cherry
C Trellis
Pears, Mini Tatura + RDI Trellis close-up Gala/M26 V trellis
growth of branches, which are bent down
towards or even below the horizontal, is reduced.
As with rootstocks, the metabolic processes
that explain why this happens are still not
fully understood. Branches that are bent down
also form more and ‘stronger’ flower buds than
branches that grow in semi erect positions.
Usually these extra and improved flower buds
set more fruits and this results in a further
reduction in shoot growth, due to the increased
fruit: shoot competition within the tree for
foodstuffs. It is primarily this principal of shoot
bending that underpins many of the modern
systems of tree training, such as the Slender
Spindle, Central Axe, and Solaxe.
Pruning and training can be used to either
increase or decrease the number and quality of
flowers produced. Tipping of the shoots of
some apple varieties can increase the number of
short shoots (e.g. dards) and hence the number
of terminal flower buds. In contrast, dormant
pruning by heading cuts generally reduces flowering
and increases shoot growth. This is not
always a detrimental response, especially with
cultivars that regularly produce too many flowers
and set too many fruitlets leading to small
fruit size. With crops for which no approved flower
or fruitlet thinning strategies exist (e.g.
sweet cherries), winter pruning, including spur
pruning, is being used to reduce the potential
for excessive fruit set on inherently small-fruited
cultivars such as ‘Sweetheart’ grown on cropinducing
rootstocks such as GiSela 5 and 6.
Unfortunately, shoot training coupled with
some judicious shoot/branch removal needs to
be repeated annually and is, therefore, one of
the most expensive management operations in
the orchard. One method of reducing this
expense is to mechanize the pruning/training in
some way and studies undertaken recently have
looked into this possibility. The problem is that
almost all of the popular modern training systems
have been developed to maximize light
interception, yields and fruit quality and no consideration
has been given to mechanization.
Trees with the popular three dimensional configurations
will prove very difficult and expensive
to mechanize and more simple tree architectures
will be required if this strategy is to be pursued
further in the future. In the short term,
therefore, traditional pruning and training techniques
will continue to provide a vital supplement
to dwarfing rootstocks in controlling tree
growth and cropping.
Plant growth regulators to aid growth control: A. ‘Bramley’s Seedling’ apple: unsprayed (left),
Cultar sprayed (right); B. ‘Conference’ pear: control (left), regalis sprayed (right); C. Influence of
Cultar soil treatments on the flowering of sweet cherry.
ISHS • 22