This series of four articles first appeared as part of Chapter 12 of my first book Bonsai Inspirations 1 and this excerpt contains what I believe to be essential information on how to design, build and improve the branches and branch structure of a deciduous or broadleaf bonsai.
Note that extensive information of how to build the branch structures of coniferous bonsai, such as Juniper and Pine, are contained within Bonsai Inspirations 2
AUTUMN/WINTER or STRUCTURAL WIRING AND PRUNING
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This article describes the pruning of deciduous tree branches in Autumn. As the leaves fall in Autumn it is the first opportunity to study the branch structure in detail since the beginning of the growing season. However, it is possible to carry out these techniques at Midsummer if the tree is vigorous and suitable for defoliation.
It is important that enthusiasts in areas where their trees will be exposed to temperatures below around -7ºC apply these techniques in the Spring when the last of the severe cold has finished.
The horticultural principle behind this timing is that the branches and the tree itself do not become fully dormant until a few weeks after the leaves have fallen (new pruning wounds made during leaf-fall will noticeably begin to heal), and any tiny cracks and fractures made during wiring at this time will also have time to seal against the cold in the depths of Winter.
It may indeed be possible to carry out Autumn wiring and pruning in colder climates than my own, however without the necessary experience I cannot advise it.
Whenever these techniques are actually carried out, they are an important aspect of bonsai development and maintenance and should be applied at least every two years to keep a bonsai in pristine condition.
The primary objectives of Autumn/Winter pruning are:
1) the pruning back of new shoots to address the balance of the branches and to improve branch taper
2) shaping of the branches with wire to improve the placement of older branches and to place the previous years growth correctly.
This is an Elm airlayer in Autumn 2009 with all of the remaining leaves removed. As can be seen in the image above, the bonsai now has an impressive number of branches (ramification). However, the branches have become messy and the true aesthetic form of the branch structure has been lost.
Within the branch structure there are also a number of branches that have ‘faults’; that is, branches whose improved appearance, or removal would improve the image of the bonsai overall.
When working on the entire structure of a bonsai, it is simplest and easiest to work methodically starting on the lowest branches and working up the tree towards the apex or crown.
Working from the bottom upwards is a good habit to get into for the enthusiast; the shape and style of the lowest branches should dictate that of the branches higher up the trunk and it is considerably easier to manipulate or even regrow the upper branches in accordance to the lower branches on a bonsai than vice-versa.
The lowest branch of the Elm airlayer has been allowed to grow freely during the growing season to encourage it to thicken.
Shoots such as these that have grown outside the silhouette of the tree are pruned back. Where there are more than two shoots growing from any one point, the extra shoots should be also be automatically removed.
As an example, this is a branch that requires pruning back slightly so it is within the silhouette of the tree.
If the 3 branch tips are simply pruned back a little the branch will then have 3 branch tips but an opportunity to improve taper will be missed.
For better taper, the main branch line is pruned back to the side branches producing more refined branch tips.
For even better branch taper in the future, the branch could be pruned even further.
The resulting growth in the Spring will quickly fill out the structure of the branch, however, obviously the tree’s foliage mass will be thinner in the immediate future which is why pruning back this far would normally be reserved for trees in development.
After pruning back all of the required shoots, the remainder are wired into shape where necessary.
All new shoots (from the growing season that has just finished) that do not grow in the correct direction or are too straight are wired to add movement and direction to them.
This step is very much part of the artistic side of bonsai and the exact placement of the branches will depend on the individual.
Some enthusiasts prefer a ‘classical’ or ‘abstract’ style of deciduous bonsai and the majority of the branches will be downward growing.
Other enthusiasts prefer a more ‘naturalistic’ style of branch placement and will try to imitate nature by arranging the branches on a deciduous tree so that the lower branches will drop downwards from the trunk but then rise gently at the tips and the upper branches will automatically rise as can be seen on deciduous trees in the wild.
Whilst the exact styling of a bonsai is down to personal taste, my personal preference tends to be for more naturalistic styling and I would encourage enthusiasts to follow this direction and avoid the more primitive abstract styles of yesteryear.