1 - When do you realize the structure trimming on the branches of your palmatum ? On forums it is advised to keep first a stub of big branches which are trimmed, in case of sap issue (sap withdraw or sap bleeding). Is it something that you do or advise to do ?
1) He cuts the whole big thick branches but leaves a stub for the thin branches.
2 - Can you explain how prunus mume ramifications are made in Japan ? With trimming scissors only or with wire too ?
2) Both trimming and wiring. After flowering you better wire branches and and cut the remaining branches. It means the timing : Wire and cut after it flowered
3 - In forums, it is said that sometimes, pine roots are soaked in a disinfectant solution in Japan, do you know what solution it is ?
3) The liquid contains the sulfer. But this solution isn't jin liquid.
4 - I read that sometimes, it is usefull to put a piece of wood under the nebari, to force the roots to grow horizontaly, is it something you do ? Do you have tips/advises to make good nebari on palmatum ?
4) No, he doesn't use a piece of wood. He cuts the strong thick roots in order to increase the number of the thin roots. He plants a tree in a shallow pot letting the roots horizontaly and then repot it in the regular pot.
5 - In Europe, some Bonsai enthusiasts don't like very much the "too perfect" nebari (very displayed like a fluent cheese) on some palmatum, or burger, or stewartia trees (cf Picture of burger below), i'd like to know if you like it ? And do you know if in japanese expositions, Judges consider those nebari as perfect ? Do you know a way to modify those nebari for someone who want to make it more natural looking or asymmetric ?
5) In Japan people like nebari. Japanese like emphasing roots because they make the tree look big. The air layering is good to make nebari but not misho (misho means trees grown from seed). Such a perfect nebari is called bankon in Japanese and palmatumn is suitable for that.
6- Do you make air layering on your palmatum or Burgerianum trees ? Can you explain when you do it, what technique you use, and do you use rooting hormone ?
6) In March he uses wiring for the air layering. Use wrap two thick wires tightly. Wire one tying it left and leaving some space up, wire the other one right (picture below). In June he peels the skin of the trunk. Yes, he puts so called rooting horomne which helps growing roots.
7 - Still concerning air layering, can you explain when it is the good moment to cut it ? how to maintain the new tree after cutting ? Any 'frequently made' errors to avoid ?
7) For the palmatum, plant them in spring. Do not let them dry. First plant them in deeper pots and repot them in shallow pots.
8 - You advised us previously to let grow some sacrifice branches for one year long before to cut them and do again the same operation during a few years to get bigger trees. Is it possible to let some sacrifice branches grow a few years without cutting them to make the trunk grow faster ?
8) It's better not because the cutting part becomes bigger and it is not beautiful. Add plenty of fertilizers and cut them after one year Repeat it three years, then the trunk grow fat.
9 - I have a palmatum "Beni Tsukasa", since last year. It grows very fast and seems strong. Do you think this cultivar is as strong as Yamamomiji ? Do you have cultivation advise on this cultivar ?
9) It grows fast. Cut the branches when they are thin. Then cut when the branches get longer. Repeat it.