Kate, a few responses from my limited knowledge on the topic.
This got me thinking though because if you look at a map of were japonicum is native, there are three very distinct populations.
You mean ones in eastern China, Korea, and Japan, true? I don't know how much they are truly distinct as they are separate. More about that later.
I believe the var with a red inner lip is called var. glabrum.
This variety, described by Suzuki in 1980, is reported only from Ibaraki Prefecture just to the northeast of Tokyo. If memory serves, the stems are less hairy than the normal type, hence the name "glabrum". I'm pretty sure this variety is not generally accepted by the international community, but is still on Japan's Red List.
I haven't been able to find to much info on what, if any, the differences are between the popuations. Ron mentioned that there was a plant in MA this is a very hardy vigerous grower. Does anyone know if that or the red lips is a specific feature of a certain population?
I too cannot comment much on this topic, but I have seen the difference between Japanese and Chinese plants. Japanese flowers tend to have pale pink lips with relatively few purple striations particularly around the lip orifice. Most of the Chinese ones I've seen have much more purple and the lip orifice can even be completely rimmed in purple. I have no experience with Korean plants. That vigorous plant Ron talks about has a Japanese origin, very likely Shikoku Island.
BTW, to my knowledge no Chinese specimens have been legally distributed outside that nation, but were all wild sourced. To tell the truth, 90+% of C. japonicum in cultivation were not artificially produced, except maybe through division.
