Mary, tell you the truth, I don't know. But in China growers always suggests Chinese variety for more northern area, Japanese variety for southern areas ( not like zone 8 south). Probably Japanese TP can handle more humidity.
With American variety I had no clue, I only have 2 of them, I think that the Rockii variety is the most hardy one out of all four.
P.s is not like the Chinese variety not hardy, but they are the earliest one to bloom, so in early spring we still have cold weather, and then it got bud blast from freeze, and this is the first year I had experience some thing like this year.
