I accidentally severed above the root zone of a 3 month old seedling. Dipped it in liquid rooting hormone and restuck it in the growing medium [ sifted gravel with a very little peatmoss [ for the sterile organic part ] ] and it regrew new roots.
Additionally, the seeds used were from a pack offered by Bonsaiboy and I figure it came from Dallas Bonsai, and obviously Japan.
I just soaked for 24 hours and planted all, even the floaters. You normally get 30 something seeds, with 25 or so germinating and thriving.
However, a year or two later as many as 10 may die, through no adaptation to our Tropical climate and often the ones that die don't grow normally, usually long and slender [ mutations? ]
I carelessly did some attempts at cuttings last year, and have so far two that are still alive and - may - be growing, but I won't touch them until December.
So a week ago I did another batch of cuttings to see if I could master this technique.
Seeds of Japanese Black pines have to pass through quarantine for us and I would prefer to just grow my own cuttings.