WillC & ShadyGreenThumb:
Thank you both so much for your prompt response. Looks like you both think pruning is my problem, so I will cut back my plant today. I'm unsure if this is a "cane" begonia, and quite frankly was unaware there were different kinds! I purchased my plant because I was struck by its beauty. Hopefully, I will be successful in starting new plants from the cuttings.
Thank you so much for your input.
Annie in Montana
