There are roughly 150 species of Begonia from China, those that are native to elevations of 5,000' and up are rare, but useful. A trip to the Kunming Botanical Garden in China impressed me with extensive greenhouses and lath houses dedicated to Begonia collection and breeding. When you look towards Begonia locales in South Africa or the Andes, you may find species living at 11,000' and above! Visitors to Machu Picchu report beautiful tuberous species of Begonias spilling from the cracks of the ruins. The Begonia species pearcii, veitchii, and boliviensis are all tuberous species living at cool, misty 10,000' elevation. Knowing this, you can understand why these plants do poorly in the American south with hot, humid nights foreign to these plants. These are the great-grandparents of many of the tuberous spp. we know today. It is my belief that through inbreeding and the introduction of different species, that most tuberous varieties have lost their hardiness. What I have seen in new collections from these high elevations is an increased ability to withstand cold.

What all hardy Begonias need is some sort of structure to store energy and food for the following year's growth. I had received a "hardy" Semperflorens begonia years ago, bred by Craig Walker. If you look at the roots of a normal "semp" begonia, they are fibrous. This one was different, with a definite fleshy "pseudo tuber" that insured new growth the following year. (See picture) Operating out of the USDA Research station in Poplarville, Mississippi, Dr. Cecil Pounders has done much breeding work with Begonias 'Kaylen', 'Barbara Rogers', B. cucullata, and B. fischeri - all showing levels of hardiness in the deep south. Dr. Pounders is doing a large number of crosses with ornamental cultivars to come up with varieties that are attractive and frost-hardy. In my recent trips to Texas and Alabama, I was surprised to find a number of rhizomatous species that took degrees of frost. Dawn Stover, a research associate with the SFA Mast Arboretum in Nagadoches was potting up a begonia with strong B. heracleifolia heritage on one of my stops there. She said that it's the one they call the "hardy" one down there. Tony Avent of Plant Delights nursery in North Carolina even lists B. heracleifolia 'Nigricans' as hardy to 15 degrees.

At issue is what varieties can take a northern winter? If you're talking zone 4 or 5 - you're out of luck. There are those who have surprising microclimates. I'll never forget that Cole Burrell had a hardy banana in Minnesota! I have even heard of South African Begonia sutherlandii thriving in a zone 5 garden under some pines! Back to our Google™ search, Begonia grandis is by far, the easiest hardy Begonia to find.