JMT: It will most likely keep it's leaves, but probably wouldn't grow much or bloom - it will take a rest when it gets cool enough. I'm surprised you don't have it in the ground - it is totally hardy in your zone.

Incarnata will keep growing if the temps stay warm, but it will need supplemental light for it to continue to bloom. It is day length sensitive, blooming during the long days of summer. I have over-wintered incarnatas indoors under lights, and even with long (~16 hour) day lengths, they still did not bloom. I suspect they also need very high light intensity.

Thanks for the information, folks. I am growing these from seed for the annual plant sale (in April) of the local Master Gardener Association, and wanted to have them in leaf, at least, at that time. They will get plenty of sunlight and temperatures higher than 50F all winter long.