Mariyln, it is important to know what kind of porterweed that you have.
There are many kinds. I am only familiar with four, the red, the coral, the purple and the blue. I no longer grow the coral, because it gets huge here and only blooms once or twice a year. The hummers love it, though. The branches tend to break off in storms.
The red one that I know is low growing and very sensitive to cold. My experience is that anything below 30 degrees for a few hours will likely kill it or certainly kill it to the roots. It is very floriferous however, and the hummers really like it. I don't grow this anymore. The ones that I had died out from the cold. (I'm in zone 9B and it seldom freezes here.)
The blue one is what we call the "native" here in Florida. I'm not sure how native it is, but it grows well and is very easy to take cuttings from. I have maybe three or four in different parts of my property. The flowers are quite small and they get little use by hummers. The small butterflies love them, as do other small pollinators.
The real winner is the large purple porterweed (S. Frantzi). It the one that Carol has photos of above. Once it is warm it is ever-blooming, doesn't need deadheading and grows big and fast. The hummers just love it. I have some that reach ten feet. They like sun, water and well-drained soil.
If you have the S. Frantzi I would recommend that you try to overwinter it. In early spring, put it in a large pot in a sunny area and feed it well. In a month or so you can put it in the ground. These plants grow well from cuttings. If yours grow big next year you might want to take cuttings and pot them up and have them for the following year.
I just took eight cuttings this morning. I expect most of them, if not all of them, will take. They will be ready for next year. I also took six cuttings from my Yellow Bells tree, (Tecoma Stans). I have never tried to take cuttings from them before, but we'll see. They are not easy to find for sale.