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Monday, October 19, 2009

Stumping or reduction cut - English

This article was written in summer 2002 and printed in International Bonsai therafter.

Stumping or Reduction Cut
By Walter Pall

When speaking of cutting trees one can define three types of cuts in general:
1)Maintenance cut: This is the one that everyone has to do when working through the tree on a regular basis. It is done on every tree, also on finished ones.
2)Development cut: When a tree is in the development phase it often needs some more ornless drastic cuts which change and improve the overall design.
3)Reduction Cut: When a bonsai gets started from a anturally grown tree one or several bold cuts are needed to define the basic future design.
In this article we speak about the reduction cut which is also called “stumping”. It is a drastic shortening of a tree which has grown for a while already. This is the decisive intervention which makes a normal tree a future bonsai, or “raw material”. It can from a nursery or a tree that used to grow in a garden or in the wilderness. Even a tree which was grown form seed or from a cutting specially to become a bonsai eventually needs such a drastic pruning at least once.
When practicing the reduction cut the bonsai designer works like a sculpturer who takes away from a raw stone or woodblock everything that he does not need. What is left is the raw material which will become a bonsai. After the cut the tree grows freely for a while. Then it will be further designed with development cuts which can be still a bit drastic. In the refinement stage usually only smaller development cuts and maintenance cuts will be exercised.
There are three methods of drastic pruning to gain a usable bonsai eventually:
1)One lets the tree grow freely until it is a bit higher than the desired height. Then the crown is formed . Usually the existing top will be cut off completely and a high branch is pulled upwards to form the new top. This will assure good taper in the crown area. The crown will be formed with development cuts to make sure it does not grow out of proportions. The real problem is the lack of taper of the trunk with this method. This major fault is almost incorrigible. Many amateurs keep such trees with nice crowns but poor trunk taper. They hope in vain to eventually obtain a really good bonsai after many years. One can try to create taper on such trees by letting some selected branches grow freely for a long time. By delivering a lot of energy they will thicken the trunk and roots below them considerably.. They will be cut off totally eventually, leaving a big wound. These are called sacrifice branches. If nothing is done god taper will rarely ever develop just by itself.
2)The second method consists in developing trees from seed or from cuttings. They are cut on a strategic point early . With the highest branch then the trunk line will be continued. One can form sharp angles in the trunk line or create straight , but tapering trunks for formal upright trees. One must know that angles in the trunk line will be corrected by the tree over the years. What was a trunk with several bends in the beginning will eventually become much more straight by growth mechanisms of the tree. This method is lengthy, but effectual. It is the professional method for large bonsai nurseries. A disadvantage is that the trees eventually will look too even, all somehow alike and often a bit boring.
3)Sometimes one can obtain an excellent bonsai with the third method. One looks for trees which have grown for quite a while and which are suitable for drastic pruning. On some collected trees nature has foreseen that they grew in such a way that with a bold cut one can get a good bonsai with good taper and good branch position . With conifers one sometimes can create an instant bonsai with such drastic pruning. Normally one will have to add a long development and refinement period however. It usually takes many years or even decades for a deciduous tree. With this method often very interesting and sometimes outstanding bonsai are created
The stumping can take any place on the trunk in principle. It is only a question of what the bonsai enthusiast wishes to obtain. Of course, it also depends on the properties of the species used. Deciduous trees often can even be cut below the lowest branch even if no visible buds exist. When a branch is positioned at a favorable place where one could cut and have the branch take over the trunk line, one should always seriously consider to use this option.
The angle of cutting is important. Usually one gets the advice to cut diagonally. The diagonal is chosen so that the usually drastic change in taper between the trunk and the new leader is diminished. It is very important to decide about the final front before the cut. One usually dooes not want to see the cut from the front because a very big would will create an ugly scar or a hole forever. This will attract the eye and always indicate the artificial intervention. Sometimes, however, one wants to include a large hole in the design of deciduous trees. Then the cut can well be in front. Conifers are usually designed with deadwood anyway. So the drastic cut can be often be used to the advantage of the overall design easily. The front will be decided by the nebari, the trunk line and the position of branches if there are any. In addition it might be changed slightly by the position of the big reduction cut.
An immediate diagonal cut however often has decisive disadvantages If the first stumping is done diagonally immediately, usually a considerable part or the trunk will die back. The cut on deciduous trees and on conifers where no top jin is planned should first be horizontally and then the tree should be left alone to do its own design job. Part of the trunk will dry back, some shoots will develop. After a few months or in the following vegetation period one can see what the tree has done and now finally cut diagonally. One takes the now existing shoots and the development of callous so far into account.. This method also has the advantage of getting many strong shoots which create lots of energy and thus closing the big wound faster.
With conifers it is much easier to stump with immediately good results than with deciduous trees. It is, of course, very important to make sure that a sufficient amount of green remains on the tree. Usually one will tend to create a top jin with a part of the original trunk. Then the cutting point can well be in front, or should even be. A tree with a top jin should always have some additional deadwood on other parts of the tree in order to look natural.
The height of the cut depends on your aim and the circumstances. Except for the literati form, usually a rather thick trunk in comparison to the height of the tree is what is desirable. One must know the foreseen final height of the bonsai. This is not the same as the height of the cut, of course. The growth of the crown has to be added. A good proportion for a bonsai is a relationship of 1:6 of trunk width vs. final height of the tree. Therefore the first cut can be set at a height which is about three to five times the trunk width. The deigner should give this a lot of thinking because this will be the most crucial design measurement in the life of a bonsai. A drawing with measurements can help here. Taking a cloth or paper to hide the part of the tree that will come off is a good method to foresee the effect. Amateurs usually cut far too high btw. This means that they have to live with poor proportions forever or that the right cut will be done at some later point in time.
An extreme reduction would be to place the cut horizontally directly above surface rootage. This can only be done with those deciduous tree species which are known to sprout readily. If the tree was healthy before the cut, numerous shoots will appear at the edge of the cut. They will later be designed into the multitrunk or clump form. Since all shoots are of the same age they are also of about the same width. One has to take care that some selected trunks can develop better than the others and therefore become clearly thicker.
The big wounds used to get covered with wound sealing immediately. It is now state of the art to leave them as they are because this does not help and can even create damage. It is of advantage if the wound is placed in full sun because it will heal faster. At least one branch above the would should grow freely for some time. This will make sure that enough energy flows down to create callous to fill the hole.
If one has placed a horizontal cut in the first place then a diagonal cut will follow after the shoots have appeared. One should only cut close to the terminal bud or shoot in the most active period of late spring and early summer. At all other times the bud or shoot that was meant to become the new leader can easily dry out. Therefore the cut is placed so that a stump is left which will dry and be removed close to the living bud in the next vegetation period with a knob cutter. With many deciduous species one does not have to be that careful however. This is especially true with very young trees. A new top will usually appear when the old one dries. It is possible anyhow that the well thought through future shape is destroyed and one has to work with a new top which is lower than the planned one. This can often be of advantage!
Generally also some thick branches have to be removed when stumping. In case of doubt one removes the branches which are situated in an inner curve. Branches should get shortened at a point where a former branchlet with a nice line can take over the new lead of the branch. If a branch divides itself into three branchlets at one point, it is almost always a good idea to remove the middle one and continue working with the other two. In the lower part of the crown, thick branches are left while in the upper part they should get removed and thin branches shold be selected.
After cutting the top and the thick branches, the tree should get fed well. The remaining branches and the new shoots can grow freely for one season. This will cause the wounds to heal faster and also the unavoidable more or less drastic changes in taper will be reduced.
After the first cut which was placed as low as possible the tree will grow freely for a vegetation period. The following next cut should be as low as possible again. It is usually of advantage to place it at the opposite side of the first cut. It is also possible to develop young conifers that way as long as one takes care to always leave enough green and buds on what is left after the cut.
It is not absolutely necessary to plan exactly how the design will eventually evolve. One can just cut low and give the tree a chance to grow at random. In the next years the tree is cut like a hedge, just for silhouette, not for structure. Then after a few seasons the tree is dug up and one works it from there and selects the best from the possibilities that have developed. This is basically what nature does when trees are grazed by animals. The animals stump the trees indiscriminately in early spring and repeat this every year. After many years very interesting little trees develop which have very good ramification and most interesting design options. The animals certainly don’t want to develop bonsai, they just bite. Thus at random much more interesting forms develop than if someone had given consideration to every cut.
When trees have weak roots and are being repotted or planted into a growing field it is often not a good idea to stump them right away. It is better to let them settle and develop good rootage fist. A tree with weak roots would not open all buds. Some would dry and some shoots would dry after appearance. A tree can only open and develop the number of buds that can be supported by the roots. Therefore it is left alone for a year and when the roots have developed well one can stump radically.
If one wants to develop very thick trunks it is better to wait a few years. Trees in a growing field can well be a few meters high before stumping. In order to reach a trunk diameter of 10 cm for the finished bonsai, the raw material at the time of the reduction cut should have a diameter of 7 cm already.
The reduction cuts will be continued until the large wounds have healed and the general structure of the main branches is set. Only then comes the time to plant the tree into a rather small pot. From then on it will only grow very slowly. Now the development and refinement phases begin.
One should consider that over the long time cycle of bonsai material development the bonsai designer also develops. Usually one wants to design clear-cut, “nice” trees in the beginning. After a few years this gets boring, because the trees all look alike - “cookie cutter bonsai”. One starts to get interested in new and more interesting shapes. At this point in time the trees which were started a few years before are ready for refinement. Unfortunately then they are too boring for the now advanced bonsai enthusiast. This is the reason one should develop material that seems just too challenging at the moment.

1 comment:

  1. How do you know if a new deciduous species will backbud/survive an aggressive stumping? Ive asked the folks at my nursery for new trees I buy but they don't seem to know (as most people want their trees big and would never do that!!)

    Good old fashioned trial and error? (...fine on a $20 nursery plant but would hate to kill a collected specimen or an expensive purchase!!)