Some of the tuberous begonias that are sold in flower at Garden centers have been grown from seed and haven't had time to form a tuber. I have found it takes more than one growing season to form any kind of a tuber. Even if they do form tubers it has been my experience the tubers range in size from a match head up to the size of a thumbnail. If you want to keep them you will have to grow them on through another season. Perhaps under florescent lights for the winter and plant out again in spring after danger of frost. Tuberous begonias don't start making their tubers/or increasing their tuber size until late in the growing season. The colder the zone you live in, the least chance you have of forming tubers in one growing season. Hope this helps.

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Okay ty, yes it does help. I wish i would have known this before i dug them up, i could have transplanted them and brought them in the house for the winter months...Before i dug them up, i cut them all down..now they are stored in a plastic bagy with peat moss, roots and all, maybe i can still save them..