Two years later in April of 2010 we can say that this is very hardy in Central Europe. We had a very bad winter, but the hornbeam looks very happy. It grew freely for tow vegetation periods. Now is the time to go a decisive step further. But what to do with such monster that only two men can carry? Well see for your self. Now I can carry it alone, but it still a very large piece of material. Next weekend I will have a much more shallow pot for it and repot it again. I might edit it a bit more and them leave it alone for another year. Reports will follow.
Carpinus orientalis, the oriental hornbeam in my eyes after having worked with many dozens of these species is clearly the best broadleaved species for bonsai in Europe.
Boris helped me today. Thank you Boris.