"According to Flora of China, this species has really a huge distribution area, even Africa, Russian Far East (so it should tolerate frost!), Australia, Polynesia. Flora of China
C. minutum is also considered as a species complex (Nitta 2011)" - Heiko Muth.
"I have heard but not seen the Russian Far East varieties, these are similar, but different in details" - Vadim Shmelev