Karen, I would like to encourage you to try growing poinsettias despite the potential problems that you might encounter. Julia's idea of finishing them off in the greenhouse is a good one. We follow this procedure at Langley School here in Virginia. The poinsettias have already been treated for pests. By Halloween, they start to turn red.
Students really enjoy observing the change of color.
By early December, the poinsettias are ready for distribution. We've done this for four years now, and never had any problems with white fly. Every year we get a few parents who want to buy the poinsettias. I hope that you were there. I would like to grow poinsettias in the greenhouse this year.