
Begonia pedatifida showing creeping rhizome and new growth
To most gardeners, "hardy begonia" means Begonia grandis, a tuberous species from China that for years has been considered the only reliably hardy member of this huge but mostly tropical and subtropical genus. That has changed as recent collections in China have turned up a number of rhizomatous species that are also fairly hardy. I'm trialing several of these in my zone 7 garden (see But where are all the begonias?) and some of them are already emerging after my area's coldest winter in 20 years.