Ask-a-Dave's-Gardener: Santa Cruz begonia?, 3 by tomforde

tomforde wrote:
For years I\'ve been growing and overwintering what I\'ve always thought are a couple Santa Cruz begonias. Their tubers have become quite large - one is over 10\" across and I need to pot it in a 15\" container. Now I\'m wondering if they might be some other begonia because the tubers are so large.

Is this unusual for Santa Cruz begonias? Can the tubers be divided to propagate? I\'ve attached a few pictures. Please comment. Thanks.