It's really hard to answer your question without more information, like: what kind of begonias? how far back did you cut them? how much light and water are they getting? A lot of my begonias spent the winter outdoors under frost blankets, not a viable option for you I know, but many are just barely showing growth at the bases of the ones that got 'cut back' by Jack Frost. They were fairly moist all winter, and we've already had some days hit 80, but the new growth is very small on some. Others were hardly damaged except by snails and falling debris from the trees. So--it depends!

I don't think you find any begonias which are hardy in a zone6 winter outdoors. If you had them indoors as houseplants, it may be a different matter, but begonias are not hardy outdoors in our zone. Sorry.

Sorry--read your post wrong I guess. Thought you were talking about begonias indoors. There are, however, hardy begonias, the most often grown one being B. grandis ssp. evansiana (I think I got that name right!) and just to be sure it would be hardy for you I googled it. There was a note from, I think, Clemson University, saying it is rated hardy to z6 but is doing well in their z5 rhododendron garden. I think there are others too, and I know there are several different forms and colors of this one. I think I've read they have found some new ones the last few years. You could check Heronswood and Plant Delights nursery catalogs--they both go on plant hunting expeditions and test things and are reliable sources of information. I think sometimes catalogs--good ones that is--are better and more up-to-date sources of information than almost any place else.

If you're talking about the hardy Begonia, they are late to emerge. I'm just now starting to see shoots at the base of mine (after pulling back the mulch). Give it a little more time.