Calamus is the largest genus of palms, native to Asia and Australia.  Calamus, along with Daemonorops and Plectocomia, are rattan palms, twining their way high into trees by grappling appendages and having vinelike stems with widely spaced feather leaves.  One of the hardiest species is C. muelleri, which is known to survive temperatures down to -7°C/19°F in its habitat in the mountains of Australia, though it may be even hardier than that.  There may also be some hardy species of Calamus in southeast Asia, as well as perhaps more in Australia.