I grow my Begonias almost exclusively indoors. The most enduring species such as Begonia venosa and Begonia peltata actually benefit from being on the south-west balcony during the summer months. All others can impossibly take the temperature differences combined with the intense heat and radiation there. In fact, not even every type of basil can take that much heat; while the small leafed type did very well, the bigger leafed type looked quite unhealthy.
No Begonia could possibly survive a normal winter here; even If it survived the temperatures well below -10°C it would have difficulties with rain and snow making the soil rather soggy at times. Adding lots of sand could help, but then it would dry out in summer. Currently, tuberous Begonias don't stand a chance either as I have no suitable storing place for overwintering the tubers.
Temperature differences between day and night and between winter and summer are problematic even indoors. Unfortunately, the central heating control is not very sophisticated; with one outdoor temperature sensor and the cellar's ceiling not insulated, easily noticeable temperature differences within one room are the rule rather than the exeption. No wonder I have to resort to heating mats to prevent the cold floor damaging the Begonias' root system.
Another problem is that Begonias have not evoled to cope with the enormous differences in illumination and day length since the come from tropical or sub-tropical climates. For this reason I installed quite a lot of fluorescent light tubes and bulbs. Incandescent bulbs are out of question as they are far too inefficient. Unfortunately, all fluorescent bulbs I find in non-specialised stores have the colour 827 (warm white) where I should have 840 (cool white) for my plants. Luckily, there is no such problem with fluorescent tubes.
Many Begonias also have severe problems with the low indoor humidity in winter, which is why I bult a sort of a plastic foil greenhouse with heating and illumination under the foil.
This system is not as airtight as a terrarium would be, so that a real terrarium is necessary for the most demanding Begonias.
Fungi are never very far away, I've just learned. It's not Mildew, Botrytis or other easily visible sort, but the meaner invisible fungi that cause the plant so suddenly collape. I probably should be prepared for regular preventive applications of fungicides.
I'd love to build a real greenhouse where I had full control over the growing conditions.
Begonias in Switzerland
You must really love begonias to keep yours alive and growing. My peltata always looks great in summer but is a shrinking violet right now. My venosa is doing okay but it seems to be a very slow grower.
Begonias are challenging enough with bringing them indoors for winter but luckily we have hot, humid weather for half the year where most of them do thrive. Lights, heat, and some kind of humidity control helps them do well indoors as well but that can get costly. It would be wonderful to have an aquarium for the majority of my plants but for now I make do with gravel trays and plastic covers (including drinking cups, cake covers, plastic bowls from salad materials, etc.) for the worst looking ones.
If begonias weren't so enchanting, I'd throw them all out and find something a lot easier to grow. Here is my biggest tank - I think it is a 120 gallon tank with 3 fluorescent lights. Most of the begonias are fairly new so they get the best attention until they put some size on and I can propagate them.
Your begonias are lucky indeed, at least in summer, since you live in zone 7b. 6a can be challenging at times, but since I once was a professional gardener I should be able to "read plants" and gain specific experience with the variuous groups of begonias.
Begonia venosa is a slow grower which needs very intense illumination, indeed. This doesn't surprise me at all, since its natural habitat are semi-arid grasslands
in Brazil. For the same reason it can be expected to take temperature differences, low humidity and wind with ease.
Although begonia venosa can be propagated by cuttings I prefer to sow them. They germinate quickly and even small seedlings tolerate some drought.
Most begonias are not that easy to propagate from seed. But even so, sometimes I don't have a choice or I choose to grow them from seed to select the most restistant seedlings.
Venosa is one of the slowest growing begonias that I've got. Very thick, rigid leaves. Not very showy but still nice to add to a collection. Peltata on the other hand is a fast grower and has bloomed for me as well. I haven't given much time to raising begonias by seed but eventually will try it (I have done rex and tuberous in the past and currently have some canes coming up from seed).
Here is peltata this past summer.
Here is venosa a year ago. The felt is more prevalent on the newer leaves.
@hcmcdole
Are you sure this is begonia peltata? My peltata's leaves are thickly felted, so that young leaves look greenish white.
http://opgc.osu.edu/image/gallery/full/begonia/436_B.kellermanii.JPG
http://absastro.tripod.com/skey/spic_np/peltata_l.jpg
Fairly sure it is peltata but since I got it from GHW it may not be (they do get things wrong). Also your first link is kellermanii, not peltata. They look very similar. Also the picture I presented had no young leaves. Here is a picture of it with younger leaves and blooming.
