I usually buy new fibrous rooted Begonias every year.
However I would also like to keep certain ones through the winter so I'm going to be watching for replies to this question. Perhaps cuttings, or could I keep seed from the ones I want Would they come true. Sorry to hijack your query Brosy.

That’s fine Feverfew, these begonias have given such a lovely show this year so would really like to keep the bulbs if possible

Well the thing is, if you don't try you definitely won't be able to, so there's nothing to lose really.! I'd put them in the garage(if its frostproof) in front of a window if there is one, and cut the tops off when they die back. When they do die back try to keep the corms dry over winter, perhaps in sand, sawdust or very dry compost, and keep them somewhere where mice won't get at them. They are certainly well worth trying to save - aren't they lovely!
profile doesn't say which county you live in so we can't assess the likelihood of heavy frost.

Thank you Steragram, we live in Kent. We were concerned by the change in weather this weekend. Obviously they are still in flower so still very attractive and as you say worth trying to save so will take your advice. Do you think we should cut them back now or wait till they die off?

That's a hard question - it depends what the weather is going to do! Have you got anywhere you could move the pots to and still enjoy the flowers a bit longer? (eg the shelter of a south facing wall?)They will not survive frost so listen out for the weather forecasts! Kent gets more cold weather than we do If you have a bench or sill in front of a garage or shed window that would push them on a bit you could leave them to dry out there too. If they were mine I wouldn't cut them back until they begin to look miserable, but I'm a bit of a softy over things like that. It doesn't matter too much if the tops get just sightly frosted as long as the corms are OK, but if its as windy at your place as it is here they won't be in a good state by morning anyway!
Good luck.

I'm in Hampshire and I wait for them to die down, they soon do once the weather turns colder and I find the tops just pull / break away from the corms, no need to cut them back, they seperate themselves when ready

When you lift them be sure to check thoroughly for vine weevils, they are VM magnets

VW magnets

Thank you all for your help, we will leave them to die off naturally as they are still attractive whilst in flower and they are quite sheltered on the patio at the moment

Are you sure that they are tuberous type? They actually look more like one of the newer large fibrous hybrids, to me.

Wow Tug, I didn't know there were such things! Fantastic.

I thought they were fibrous rooted ones also, which is what I want to know about. I would like to keep a couple through the winter. Is it possible?

They're hybrids between wax begonias and some larger species from mid elevations in Brazil. The shape and color of the leaves made me wonder. They were bred for climate adaptability, so they should be fine as long as they are kept a few degrees above freezing, and have good drainage.

Brosy, I just revisited this question because I'd never heard of wax begonias but just discovered they're what are more often known here as fibrous rooted ones. I have successfully kept those as house plants over the winter so would bet that your cross ones would behave similarly. In any case, do try it and let us know - they are really spectacular and well worth the effort don't you think?