Good Morning,
I'm enjoying the Begonia talk, and I really will be keeping my eyes open as I'm out and about. The main and nearly only Begonias I have are the red and the white Dragonswings. They are the old fashioned unhybridized one popular in older days with the solid dark green leaves that look lacquered red on the underside and get about 5 feet tall.
I have left them out evety Winter, and they have survived really cold temperatures, but the are in a huge ceramic pot (way to big to move) next to the wall of the house and under an Oak tree. I do bring a few smaller ones into the garage or greenhouse though...