I don't know if I should waste your time responding since down here next to the gulf practically lots of things are 'hardy' that wouldn't be rated that way, and I haven't tried those specific varieties. But some years canes I've left in the ground come back, at least once in August(!!!)which sorta left me with the feeling that it wasn't really practical to do that. Many rhizomatous and canes for me can come back from the roots, even after a relatively cool winter--but that's not been very cold here since about '89. Upper twenties I guess. What do I know?

I also brought back Metallic Mist from PDN and am trialing it for hardiness; I have one in the greenhouse and one in the garden (divided the plant before planting it out). Both plants lost their leaves (from what I've read, this cultivar tends to be deciduous anyway, which is always a plus for outdoor survival), and both rhizomes appear to be intact right now. The one in the greenhouse is starting to push new growth, so I'm cautiously increasing the frequency of watering.

B. boliviensis does well for me in containers, but I don't think I have the drainage to carry it over the winter. I take cuttings in fall, and they are robust young plants right now, ready to be planted out. I have to think about this with lots of the things I bring back from PDN. If you notice, most of the things that are marginally hardy there are planted on berms; wish I'd had the time/energy/money/foresight to do that here when I built my garden.

Begonias that I've grown long enough to consider completely hardy here are B. grandis (all forms), B. sinensis (both the pink and white forms, which are definitely not the same as grandis - one may be a subspecies of the other), B. sutherlandii, B. formosana, and the tall, clumping white wax heirloom variety. This last is probably B. cuculata (sp?), but PDN sells it as "Barbara Rogers" - I got mine from my grandmother 20 years ago.

I think the key with most begonias (heck, most plants in general) is to let them dry out slightly between waterings. I've even managed to grow some tuberous varieties during our inhospitable summers by protecting them from heavy rains and overwatering.

Update on the begonias: B. chitoensis is dead, dead, dead but was very easy to propagate from leaf cuttings taken last fall so I have a few more to experiment with this year.

'Metallic Mist' did indeed prove to be hardy, but it was a very mild winter (lowest all winter was 16 or 17 degrees) so it wasn't much of a test. Unfortunately it turns out to be irresistible to slugs; it has tried several times to send up new leaves but they have all been eaten. So while technically hardy, it looks like it won't survive long enough to put out new foliage. Again, I took leaf cuttings last fall, but it wasn't quite as easy to propagate so I only have a couple of plants to put out this spring.

'Metallic Mist' survived here (Southeastern VA) as well, but we had a similarly mild winter. I'm growing mine in a dry-ish shady corner, which may be limiting predation by slugs - I'm finding begonias to be very sensitive to overwatering here; Rex types and tuberous hybrids tend to be hard to carry through summer, so we'll see how it does. This unusually cool spring has been right up its alley, though!

I also purchased 'Metallic Mist' from PDN this spring, & you're right, it seems to be a slug magnet. Did the leaf cuttings work for you?, I might try to double my chances for success...