If you're happy with the soil mix; leave them potted. Do NOT let them freeze! The foliage will begin dying long before it get's frosty. The pre-made pot would be easy to tell as the tuber will not be planted very deep. If it's fibrous type, it might do better as a houseplant over winter. I find most of the fibrous types don't over-winter very well.

Once the foliage fails; cut it off flush with the tubers.

So they must have a natural period of dormancy they require.

I'm hoping we may have another month before first frost, but there are always surprises. There's no sign of slowdown, they're blooming heavily. Some got a late start (they were started outside and it was just too cold).

The pre-made hanging basket one is a knockout. I've GOT to keep that one alive for next summer! The leaves and flowers do look tuberous-type, though leaf form is larger and a little different from the ones I bought bagged as dormant tubers.

Hi linnea;

Tube begonias will not survive winters in ground in your location. After hit by frost, cut stems to the ground. Store in a dry place for a few weeks. Then, gently remove soil, roots and stem. Sprinkle with a fungicide and put ind a paper bag to distribute the powder. They must be stored where its dark and very dry. You can also put into dry peat moss, sand or vermiculite for storage (at about 50 degrees) as long as it's kept very dry. Caladiums are treated the same way.