It is a well-known fact that defoliating a Bonsai tree will enhance the growth of smaller leaves. I have also read that it allows more enhanced ramification as well. I have never tried this technique before, but am also in the process of designing and babying a small Zelkova into something resembling a Shohin Bonsai. This tree was carved and repeatedly pruned until where it is today. A lot of time and work still lies ahead. One of the things that must be done now is to reduce the size of the leaves.
Out comes the researcher in me and I start to do what researchers do. First step is to Google the term “defoliation”. An interesting phenomenon is that a lot of information is available on the defoliation of Cannabis plants. I have not tried to “Bonsai” one of those, but it makes sense that people who do grow these plants, do. I have also found information on the defoliation of other “forage” plants. This is done to stimulate the growth of more leaves as it is used to either feed animals or people or in the first mentioned case, smoke it (maybe it is for medicinal purposes). It is also mentioned that it stimulates overall growth of the plant.
Back to Bonsai. As said, the main purpose of defoliation is to decrease the size of the new leaves. The definition is self explanatory. It is the stripping of leaves from the plant. As leaves are the main centre for photosynthesis (producing food for the plant), one must be careful that it is done at the right time of the year as well as on some deciduous trees only. Please take note, not all deciduous trees can be defoliated safely. The best time to carry this process out is after the new spring growth has hardened off. Mid-summer is good for this. This allows the plant enough time before autumn and winter to grow the new smaller leaves. One theory of why the new leaves are smaller, is that due to the lack of food (less photosynthesis), less energy is available for the new growth. Another theory is that plant hormones (auxins) come into play and inhibit the growth rate of the new leaves. What better example do we have than some plants that can be grown from leaf cuttings for the actions of auxins in leaves and leaf stalks in evidence.
It is also mentioned that it is better to leave as much of the leaf stalk as you can when defoliating a tree. This also has to do with the action of auxins, but to me a more pressing reason would be that the bud at the base of the stalk is protected if the stalk is still in place. I found it easier to lift the leaf up and to cut it from underneath as the stalk is more visible from that angle on especially deeply indented leaves at the base.
It is also mentioned that defoliating a tree will lead to more intense autumn colours of the leaves. This is probably due to the fact that a much smaller space of time is left to produce food for the plant and that an accumulation of sugars in the leaves lead to these more intense colour changes.
Another positive addition could be that this process will also lead to good budding closer to the trunk as these areas will now also be exposed to more sunlight.
I have now done the deed. By the way, make sure that you have a lot of time available as this is a very time consuming task. This small tree took about an hour and a half to defoliate. Other Bonsai Blogs also have more information on this process. My intention with this blog is to start a photograph trail of the process. I will post new pictures as soon as the new leaves emerge until we get to Autumn.