Q.Caring for potted yellow begonias
Need help caring for potted yellow begonias purchased in autumn last year. They are still blooming! I bought 2 beautiful, blooming yellow begonias. One from Longwood Gardens in Kennett Square, PA. and the other in Maine greenhouse last fall. They are looking a little straggly now, but continue to have blooms. I thought one is supposed to winter over by cutting back on water so they can rest. But every time I think I can stop watering them, more blooms appear on each one of them. Very, very prolific plants. If these are the type that cannot be allowed to go dormant, how then should I best care for them?
Can I CUT BACK the leggy stems? They are so long, tall with blooms at the very top of the stems. The blooms are beautiful but the plant stems look terrible. Both plants appear to be healthy. They have traveled with me from Pennsylvania, to Connecticut and to Maine, back to Connecticut, and Tennessee. NOTHING stops those blooms from coming out. Quite lovely. I don’t know what to feed them. I want to cut back the stems, but am afraid such a move will shock them or kill them. Can you help me with this? I do not want to lose them.
Thanks very much. I do not have ability to upload a photo. Computer is PC and not compatible with my Iphone device.

Wax Begonias can certainly be maintained throughout the winter months indoors without a dormancy.
Continue to dead head the plants and prune them back to maintain a healthy and bushier plant shape.
Here is a link with more information.