I looked at this issue recently, and the lists on the web aren't very comprehensive (I never saw cryptomeria mentioned, or the trees I was interested in). Not enough research/data apparently. So it may not be possible to know until you see any effects. :( Interestingly, in the woods nearby, a sugar maple is growing right beside a black walnut, and has grown strangling surface roots around the BW trunk, which is declining badly. So sugar maples eat black walnuts for lunch...

Any kind of seedling needs light, and heat. Like a heat tray underneath the seedlings for about 12 hours on and 12 hours off. Seedlings need humidity to grow, too, (most of them, as it really helps them grow quite well) and they are still a crapshoot. They need moisture, but not WETNESS, and you'll often be waiting weeks for the little guys. If you don't have a lot of sun, it is necessary that you get a grow light/lamp for them. Growing seeds isn't recommended for beginners, as it's very difficult and many things can effect the seeds. I'm a beginner myself, and I was truly looking into growing seeds... but it can be expensive and time consuming. If you're willing and ready to go, then I wish you great luck! Look up what time of soil the seeds need, how far to push them into the soil, how much light and warmth they'll need, how quickly they grow. You'll most definitely need a grow lamp.Cryptomeria grow in forests on deep, well-drained soils subject to warm, moist conditions, and it is fast-growing under these conditions. It is intolerant of poor soils and cold, drier climates.

If you start out small, you can get a few years before it just gets too darned big for most containers. I am extremely fond of this selection and use it frequently in my designs....but in the ground :-) IME, it just grows too big too fast to be very well suited for container culture for long. And although I grow a good number of conifers in containers, for the most part, they are very slow growing dwarf forms And under the right conditions, it gets even bigger than I expected!! Saw one in a private garden the other day that was planted in the early 70's (soon after its intro to the US) that was easily 40' tall and towered over the surrounding Japanese and vine maples!! But a drop-dead gorgeous tree.

Agree PR and I think this is why the good looking Cryptos (and Cunninghamias) on the east coast are on good deep soil like old farm sites (my garden - was a farm field from at least the 1780s according to my research!) and/or in locations where they were nursed through droughts during their establishment years. OTOH over in Harford County, for example, there was one at the site of a Pizza Hut whose site was definitely graded into poor clay subsoil with excavation equipment. So it was on a south facing slope in crap soil. Since I moved here 15 years ago, it was always a hellish, haggard looking mess of a tree. They finally cut it down a couple years ago. (I never eat at pizza hut but it was near a busy intersection!) What is also predictable is the cold of an East Asian winter. There is a lower likelihood of swings because of the Siberian High pressure system. * - PS, not to say farming, per se, would 'improve' the quality of soil, but to say farmers would tend to select sites where their crops grow well. And sure enough the old USGS soil survey map for my county says my area has a better than average soil quality for farming...and gardening apparently! Knock on wood but there is not a single brown branchlet on any crypto I've planted, and some are well over 30' tall now.