My begonia plants in pots got wet and now the foliage and the flowers are ruined. They are taking on a whitish color and drooping. I wanted to save the plants for next year. It is Oct. 9, so I wonder if it is too soon to cut the plants back and put them in a dry place.
I would definitely cut them back right now. Then dig the tubers out, lay them on newspaper so they can dry out completely--about a week. Then cut back any remaining foliage and shake excess soil from them. Next step: dust them with sulfur to prevent fungal disease in the tubers. Store them individually in paper bags, or in a larger bag with newspaper in between the tubers. Place them in a cardboard box in a cool, dry place.
I'm assuming you've done this before so you know what a healthy tuber looks like. If the tuber appears to be shrunken and mushy, discard it. Here's more information about overwintering begonias.