I agree with Alain. It's definitely not for the impatient, but is worth the effort and a whole new way of appreciating bonsai. All my JWP are from seed, and this year I sprouted over 20 JWP from seeds imported from Japan and from seeds I collected from JWP growing in my yard. The ones that were imported all sprouted this spring, but died after a few months because I accidentally left them overexposed to direct sunlight. Next time I'll know better to leave them in full shade when I'm out of town. I still have one seedling left that sprouted the previous year. It's doing very well, and its candles are already swelling in prep for next spring's explosion of growth.
Although many bonsaiists want to preserve the genetic uniqueness of certain cultivars, I find the genetic diversity amongst JWP seedlings fun and fascinating. I have 4 JWP seedlings I purchased from Julian Adams, and 2 of them have roughly 3 more years to go before they can be planted in a bonsai pot for shohin. One of them has a distinctly short silver-blue needles, while another one has even shorter emerald needles. Some seedlings are more vigorous than others. If you take the correct measures, you can have pretty decent JWP bonsai in 10 to 12 years from seed (not that long in bonsai time). I have a 9 y/o with already a 1.5" trunk and flaking bark. It was root bound then I purchased it in it's tiny 5" nursery pot. If it had been grown in a colander from age 4, I believe it would have been ready for a bonsai pot by now.