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Monday, February 11, 2013

Refurbishing a Japanese maple - the "hedge cutting method"

translated from German into English by Michael Eckardt,
 President Kitchener-Waterloo Bonsai Society Kitchener, Ontario, Canada

Refurbishing a Japanese maple - the "hedge cutting method"
 by Walter Pall

 Every bonsai book describes how to work on deciduous trees to obtain the best possible ramification. All books recommend pinching. That means that immediately after the first bud break, the new shoots are pinched back to one or two buds, and that shoots that don’t grow suitably, are removed. The stated goal is to avoid long internodes and to force the tree to produce visibly smaller buds and tinier leaves with its second flush. With that, the tree is said to reach a fine ramification over many years.

Truth be told, a tree is badly weakened by the removal of the early new growth. As a consequence, it can only build weak “starvation” buds, which indeed will grow smaller shoots. This second flush is then clipped off again, and the tree is weakened even more. Eventually, they tree will become so weak that it might die.
 According to my observation, this is a very questionable horticultural practice. This method only works to maintain a finished tree for some time. Eventually it will be so weak that one has to bring it back to health by encouraging strong shoot growth. To pinch a tree during its developmental phase is pointless any way.

How is it going to grow, how is it to back bud, if it doesn’t have any strength? I have seen a whole lot of trees that were run down in this way. How did this misinformation arise? Well, a few decades ago when the first bonsai trees were brought to the West, the purchasers asked how they should care for these trees. The answer was given so that no mistakes could be made. It was assumed that the owners wanted to keep the trees in the state in which they purchased them. The pinching was recommended because it is useful for trees that are ‘finished’ and ready for exhibition or sale. Nobody thought at that time that the Westerners would ever be able to develop bonsai themselves.

 In the developmental phase, the goal is clearly to improve the tree. The trunk and the branches must be thickened, pruning wounds must close and the tree is to develop so many new shoots that one has a choice of useful branches. The nebari should also improve significantly. At this stage, the immediate image is secondary to the future beauty. That is why leaves can be large and the tree can look ugly for the longest time. To achieve these goals, the tree needs as much excess energy as possible which it can only obtain through the photosynthetic activity of as many leaves as possible. If exactly those sources of energy are removed too early, then the tree can’t develop. In the worst case, it dies a slow death.

 Well, it happens that most of our bonsai are not ‘finished’ trees, but that they are likely in an early state of development and we want to take them further. Even imported tree that look pretty good have to be developed further. Therefore it is important to know the steps to develop trees successfully.

 For decades I have been using a method successfully which is pretty much the opposite of the normally recommended approach. You can look at my picture gallery to get an idea if my method works, or if it harms the trees as many people think. All my broadleaved trees - even the most valuable and best known - have been treated this way for decades. The following example discussing the restoration of a Japanese maple is valid for many broadleaved species. To begin, the tree has to grow as much as possible to have as many leaves as possible that, in turn, develop the energy that ends up in new buds and new growth. If the first flush in spring is allowed to grow freely, then the shoots grow very long. After about six weeks they harden off. The numerous leaves produce lots of energy in the form of carbohydrates that moves downwards through the branches and is deposited in the branches, the trunk, and finally the roots. The result is that branches and trunk thicken, that the surface roots - the nebari - also thicken, and that the roots grow strongly. At the same time, many new visible and dormant buds develop. The entire system “tree” is strengthened and it has good reserves for any setbacks. A radical cutback is such a setback.

 In Central European climate about six to eight weeks after the first flush, in our area from the middle of May to the beginning of June, the tree is then cut back with big sheers to its previous silhouette. It is irrelevant where exactly it is being cut, or if any leaves are cut. This actually ought to occur as a partial leave pruning will allow light and air into the crown of the tree. All other growth inside the silhouette is not touched but strengthened with this method. And the tree is strongly encouraged to bud out again. Many dormant buds react to this radical cutback and break, even on old wood. The tree experiences the radical cut back as a trauma and over-reacts because it can mobilize much stored energy. It produces visibly more buds and activates dormant buds than it otherwise would. Exactly like after trimming a hedge. A hedge keeps getting denser if it is cut properly. Excessively long internodes tend to grow at the end of new shoots and they will be cut off with this method. This method, therefore, doesn’t create the feared long internodes. Even the largest leaves grow at the end of the new shoots and are removed completely.

 The second growth is then left until early August when it is also cut off completely. The beginning of August is an important time in Central Europe. Any later and the new shoots may not harden off in time for winter. Usually, the tree needs six to eight weeks to the beginning of October to harden off. Afterwards, not much grows. It can lead to big problems for the tree when it is cut after the beginning of August as green branches will not survive the winter.

From the beginning of October to the next March, the crown can be cut again. During its dormancy the tree will not be encouraged to bud out again. When the leaves are off, one can finally see what was produced over the summer. The entire crown has become much denser, and there is much that needs work. Many branch stumps are created that must be removed now. The same with dead branches or parts of branches. But there are so many shoots that one can chose with which to work - the others can be removed completely. Sometimes you even have the problem of having too many branches to chose from. Most of the little branches will be cut back to one bud (opposite budding trees like maples) or two buds (alternate budding trees like hornbeams). In some areas where the crown needs developing less is removed. As a result of this work the tree will look quite beautiful. At this point, you can also recognize which branches should be changed in their position. They can the be wired the traditional way, or moved with the help of guy wires.

 In addition to the ‘hedge cutting method’ you can use sacrifice branches in special situations. When a branch or trunk need thickening in comparison to others, just leave a few branches grow during the entire growth period. They can grow to one meter or more. The rest of the tree is treated as described. This way, the branches and the trunk beneath the sacrifice branch will thicken and the nebari will strengthen. This method is especially useful to improve the lower branches that normally don’t thicken because of the apical dominance of most trees. The example tree, however, is just the opposite - it is basally dominant. It’s upper branches are weaker and they are specifically strengthened with sacrifice branches.

 Broadleaved trees can be markedly improved when this method is consistently applied over a number of years as the featured maple demonstrates. When it finally is ‘finished’ one can pinch again, especially when it is to be shown at an exhibition. At this point it will be showable for a couple of years - the goal for all bonsai enthusiasts. But eventually, the tree will deteriorate and has to be strengthened again with strong, new growth.

 The disadvantage of my method is that the tree can be shown only rarely over many years. There’s always something that isn’t quite right: too many branches, guy wires, a altogether neglected appearance. Temporary beauty is deliberately sacrificed for future quality. But top trees can only be created this way. If you don’t want his, if you are not ready to pay the price for quality, then you have to live with the fact that your trees don’t improve, and even deteriorates over time. But you can enjoy looking at their beauty for some time. And this is exactly the advice we received from Japanese gardeners decades ago.

 Picture 1: 2008-05: The tree arrived in my garden in this state. The previous owner had kept it in Akadama mush and thought that he would automatically improve the tree by pinching. The crown is much too wide and flat and the leaves hide poorly structured branches. Many branches are dead. The Nebari could be much better and the maple is planted too high in its pot.
Picture 2: 2008-05: The much too dense substrate lead to severe damage in the upper parts of the crown. Many small leaved varieties of Acer palmatum are basally dominant which means that the lower branches tend to be strong while the upper branches might be abandoned. This is exactly the opposite of most other trees. The picture likely shows the rear of the tree, although the nebari appears to look better than from the front.
Picture 3: 2008-05: The first step was a strong cut back. The silhouette is deliberately kept a little smaller than ideal to allow room for additional growth. If you were cut back to the ideal shape, then the crown would soon grow too large and would have to be cut back hard again.
Picture 4: 2008-05: I would have loved to free the tree from the compacted Akadama, but it was clearly too late in the year. It would have been possible in the fall, but it wasn’t that critical. In any case, the nebari was worked out strongly. It already was a big improvement. The tree is not positioned well in its pot.
Picture 5: 2008-07: Because this variety is basally dominant, the top has to be strengthened by allowing some selected shoots to grow freely. The center trunk ought to be the biggest and thickest. If it is not worked on actively, the exact opposite happens. Especially this trunk must be strengthened by using sacrifice branches; otherwise it could even die.
Picture 6: 2009-01: A deciduous tree can be much better evaluated without its leaves. It is now apparent that the center tree ought to be much thicker and somewhat higher. The previous owner didn’t achieve much by many years of pinching. It looks rather poorly developed. The pot by Bryan Albright seems over powering.
Picture 7: 2009-04: The maple was repotted into a better pot from Japan. Most of the compacted Akadama was removed. The root ball was heavily reduced and the roots loosened up. For the substrate, many materials are suitable that don’t break down in cold and moisture. In this case I used expanded clay with 15 % rough peat. This allows heavy watering and feeding without having to worry.
Picture 8: 2009-11: The development in two growth periods is already well advanced. The branches are better ramified, the main trunk is stronger, and the nebari is improving constantly. The crown is still a little too flat. Now is the best time for detailed work on the crown.
Picture 9: 2009-11: The sacrifice branches in the crown must not be allowed to become too thick, otherwise they will develop ugly scars. That is why they are removed entirely and regrown in the next summer. The crown is worked on with a pair of pointy sharp scissors. Dead branchlets and branch stumps are removed. The branches are cut back to one or two buds, and those that grow into the wrong direction must be removed completely.
Picture 10: 2010-03: Two years after the restoration, the tree is looking pretty good. Japanese maples are very handsome trees that in each season look different but always lovely. This is especially the case in spring. Despite this, the crown must be developed further - contentment is the end of Art.
Picture 11: 2010-10: The tree looks very good in the fall too. Yet this is not yet the time to exhibit the tree. The trunks must continue to be corrected. With strong guy wires they are forced into new positions. It is advantageous to exaggerate somewhat because the tree will spring back a little anyway.
Picture 12: 2010-11: After the guy wires were removed and the crown was carefully cleaned out, the tree was - for the first time - truly ready for exhibition. Of course, there are still problems. The large wound on the front trunk is ugly to look at at. But there’s nothing to be done except to wait for many years. The middle trunk is now clearly the highest and the crown isn’t entirely flat and even.
Picture 13: 2011-03: It is tempting to see this lovely new growth as a signal that the tree is ‘finished’ and to enjoy its beauty from now on. But that would be a compromise over the long term. The main trunk must continue to grow strongly, the wounds must heal, and the nebari can be improved much. But something like that doesn’t happen on its own - it requires a lot of work.
Picture 14: 2011-04: Here you can clearly see that pinching was completely avoided. The tree was allowed to grow out fully. Six or more weeks later, the new growth has become fairly long. Now, the crown is cut quickly with a hedge pruner. In deed, it is like pruning a hedge. The exact cut is not important, and it even doesn’t matter if leaves are partially cut. Only the long term success counts.
Picture 15: 2011-10: During the summer, the tree was cut twice with the hedge pruners. Selected sacrifice branches were allowed to grow unrestricted. Momentary beauty is sacrificed for long term quality. It will be a few more years like this. This is the only way to turn an average tree into a top bonsai.
Picture 16: 2011-10: In the fall, the tree’s crown is cut again with the hedge pruners, even the sacrifice branches. As long as there a leaves on the branches it doesn’t make much sense to look too closely where and what is being cut. That will happen in a few weeks when the tree is bare. The picture shows real hedge pruners.
Picture 17: 2011-10: The result doesn’t look too bad at all. But the tree was designed for its winter view. As long as the leaves are on the tree, you can’t really see it. The crown is nothing but a big ball of leaves. Amateurs usually prefer that a tree looks good in the summer, but pros prefer the winter image. A compromise isn’t always helpful and usually leads to weaknesses over all.
Picture 18: 2011-11: Four weeks later, the leaves are removed. The crown is now carefully pruned. At this point you can only guess at where the sacrifice branches once grew; the wounds are growing out well. Two of the trunks in the group must still be forced into a better position. Unfortunately this is only possible with ugly guy wires.
Picture 19: 2012-04: This view is reward for all the work. The guy wires are only removed for the pictures, and then reattached afterward. Because the rest is almost perfect, the big ugly wound in the front tree is now very apparent. Although it has healed noticeable since the maple was able to built much energy though it lush growth. The main trunk could also become much stronger yet - but this is whining at a high level.
Picture 20: 2012-12: It is November and the leaves are removed again. One can clearly see that some branches are too long and a few ugly branch stumps were left over. The tree is now cleaned out with a pair of pointy, sharp scissors. In a few years, one should get the feeling that Mother Nature is the best artist, and that she creates the best crowns. The hand of man will eventually become invisible, even though he did so much.
Picture 21: 2012-12: Slowly the tree is turning out as it should. The crown looks balanced and the entire group looks as if it had gracefully grown on its own. This, perhaps, gives the viewer the idea that something like this is result of a hands-off approach. The development so far, however, teaches the opposite: only through strong and very focused interventions over many years can such a natural shape be developed.
Picture 22: 2013-02: The tree was repotted into a very suitable pot by Walter Venne from Germany. The results of the development thus far are quite presentable. But is is by far not the end of the development. Much has changed in five growth periods, yet the work continues as before. In another five years the tree will be better again. The drawback, however, will be that he tree is not really presentable during much of that time.


  1. No comments yet? I found your blog via some youtube videos. I am so glad that you share your knowledge, passion and wisdom freely with the rest of the world.
    Despite most people would consider you an expert or even arrogant while you speak about your understanding of the art of tree shaping and growing, to me you appear very humble and passionate about bonsai :)
    The foto series and your detailed comments are very helpful. I just started with bonsai some weeks ago, but already feel like you saved me dozens of mistakes I would have made myself.
    I love how you try to model nature and be inspired by the trees that mother earth produces. Keep up your amazing work. I hope that many more trees will have the pleasure of working with you :)

    beste Grüße,

  2. Walter thanks for the practical experience, of which there is no substitute. Sometimes the answer is right in front of you. Now I no longer wonder why my maples growing in the ground look better than the ones in pots.
    Chris Schmuck

  3. Incredible information! Thanks a lot for taking the time to explain all of this in such detail, I learned a lot.

  4. I hedged my maple a week maybe two weeks to early. Did I just basically Rob my tree of some growth that it could have gained if I had allowed it to grow a week or two more? Also I didn't hedge as much as I should have to allow for that extra room and im wondering if in 2 weeks I can cut it back a little passed the silouette? Thanks

  5. I bought a Japanese maple from my Local bonsai club. This morning I hedged the maple but didn't hedge past it's silouette to allow for the room for new growth because I noticed after I had made my first pass to then inspect if I should cut it further back that I was a week (10 days ) early. Some shoots we're almost a foot, im in central California and we didn't have much of a winter thus everything has bloomed earlier by a few weeks around here. Anyways can I hedge it a little passed the silouette in a week or two or should I wait for the second flush and next time do a better job of timing when I cut it back then?
    Thank you