I've had problems too, in the past. My basement is simply too warm. I think they do better left in the pots, I know some people use the refrigerator, too, if there is room.In an old book about begonias from the 1940's it is suggested you check them monthly to make sure they are still firm.

Thanks. The closet is the coldest place in my basement, but like you said, it is just not that cold. About half the pots have only the begonias and caladiums left in them, so could be easily stored whole. About half the pots have ivies and such planted in them, that I carry over, so I have to dig out the begonia tuber (corm?) to store. Though come to think of it, maybe I would be better off digging out the ivy and transplanting those to small pots? Then storing the pot with begonia. I keep the ivies because I have some unusual ones.

I have seen that recommendation, too, to "check them monthly." But then, I think, what do you do if they are NOT firm? Scold them?
:)

It does seem to be a matter of trying to guess how your environment is going to affect storage The lady from the l940's (Bessie Buxton) said you dip them in warm water monthly to keep them firm. What she didn't say was what to do if they have started to dry and shrink. In that case I think you may be able to keep them moist and get them started, and grow them on although the middle of winter is not the best time to try and grow tuberhybrida starts! Do not scold, swearing will probably make you feel better.By the way, does anyone know what happened to Andy of Golden West? Even his old posts have been removed from this site.

I google 'overwintering tuberous begonias'. Then I chose the provenwinners.com site, to find info. Going to their site directly, click 'Learn', then search tuberous begonias. They have info on overwintering other begonia categories, as well.