|Another question, should I be growing them in the ground outdoors, and what is the lowest temperature that they can handle? If they can be grown in Winder, GA, should I keep them covered during the winter months?
You are a little too far north for plumbagos to be perennials in most years. If they are not in a protected location and mulched well I don't think they will be dependable survivors. They will be killed by temps in the mid to low teens, maybe even a little higher. I would consider container culture or sink containers in the ground so they can be dug easily for wintering in a protected spot.
Hope this helps with your gardening question!