I am new to Japanese Black Pines, prior to last winter I did not own a JBP, therefore I decided to buy seeds online. I don't know why, but I ended up buying 150 JBP seeds from The Seed Vine on ebay. The Seed Vine actually ended up sending about 160 seeds.
Late August 2020
I followed the instructions provided, refrigeration; soaking etc. I then placed the seeds in seed trays. 144 seeds in two of these contraptions and the rest in an open seed tray.
The seeds that didn't sink (approx 10), I planted anyway but they did not germinate - as expected.
Of the remaining approx 150seeds about 120 germinated. The seeds in the covered trays sprouted significantly (weeks) prior to the open tray. I then lost all of the seedlings in the open tray to birds. As they sprout the seed husk remains on the foliage and the birds try to eat which ends up having the whole seedling plucked from the tray. (Note to self - keep trays covered)
I expect that I could have been more successful in germination if I didn't plant some seeds so deep?????

Media: I used propagating sand in the seed trays.
11 October 2020
Once the seeds were of sufficient size I moved them to 100mm pots
Media: a blend approx 50:50 standard bonsai mix from Damian at Ology and some commercial potting mix I had laying around.
After approx 2 weeks I began fertilising with Osmocote with a NPK of 21.2/1.9/5.7; Seamungus and fortnightly feeds of Powerfeed.
Over these past 6 months I have lost a few. Some decided they didn't want to play anymore; I lost about 4 to birds knocking pots off my benches when I was away during a very warm weekend.
I now have 96 JPB
30 April 2021
Some Examples
And this little battler - 45mm Most of the 96 JBPs are now between 160 - 210mm
Movement: I did not wire the seedlings, however once the seedling was tall enough to I leaned the plant to one side and fashioned a wire hook across the trunk fixed to the pot, essentially the seedling is bent to one side. I then faced the top of the seedling south. This encouraged the seedling as it grew, to grow towards the sun. When it have grown sufficiently I repeated the process by bending the trunk, using a hook ,at 90 degrees to the first bend. I kept both hooks in place for a few months and then removed the hooks in late February.
Questions:
As I said at the start, I am new to JBP, so I have some q's:
1. Is 210mm growth usual for first season?
2. I have seen recent posts with people de-candling at this time. Should I de-candle a 6month old tree? (Note some have upto 5 candles forming?)
3. Roots are visible at the bottom of the pots, should I leave it until spring (or just prior to Spring) to repot? Or slip pot to a larger pot now?
4. Most pots still have Osmocote and Seamungus on the surface. Should I remove for winter?
Looking forward to your help.
Jason