2) if so, how do you start them? So far I only raised annuals and veggie, never woody stuff.
Do they need cooling/ freezing?

I thought I would pop them in a fridge for a while, put them in a pot and store it in a sheltered spot in the garden.

3) about P jamasakura:
has anyone further information on this species? Only thing I found in the net was: common mountain cherry, height about 36 feet.
Anything about foliage or flowers?

I guess that it is somewhat plain,
(and the showy ornamental cherries are P serrulata, as far as I know.)

It is probably an experiment, and the seeds seem to have mainly sentimental/emotional value for the friend of mine.

Any suggestions are welcome,

thanks a lot, Lin

Species can be spectacular in bloom, is considered nicest wild cherry in Japan. There are a few in public plantings in Seattle, a couple pink forms across from a friend's house look like 'Akebono' from a distance when in flower. Sheets of seedlings sometimes come up beneath them. However, a nurserymen friend trying the seeds got very poor germination.