Chris has it head on.
S.rubra is interesting, its different than other Sarracenia. First off because no one really has figured how to classify the plant. Species & sub species. While plants like S. jonesii & alabamensis have been tagged I don't think its done yet.
I disagree with some of the old school, believe me I am old school with carnivorous plants. In the old school thought S. rubra grows in drier habitat than all but S. minor. ..But in cultivation you grow it more moist and you will get bigger plants. I'm here to tell you S. rubra does not do good very moist, at least none I have seen in 25 years of growing them. They are very picky and fungual attack can wipe em out if too wet. Now I know every ones growing is different and what works for me may not work for someone else.
Listen, in habitat S. rubra wherryi grows with S. leucophylla or alone. S. leucophylla can adapt to alot. Not S. rubra wherryi, you grow this plant moist to slightly moist only for best results.
S. rubra gulfensis, wherryi grows with alot of medium grade silica sand- 40-60% in with the peat. Must have drainage. The coastal form in Carolina does do better in cultivation more moist,... but thats not where they grow in habitat. They are up higher. Its not nice to fool with mother nature. Grow them as you would S. minor.
As for the far southern location. S. rubra sub species are located throughout the piedmont & mountains, or the hilly gulf coastal plain. In NC S. rubra grows in coastal locations, but the plant grows cooler inland and most are inland. Spend a cool Jan evening norh of Mobile Al and you will understand this ain't the sub tropics. Just winters are shorter and warm spells occur between the more frigid nights. S. rubra is tough, but unforgiving if kept too wet.
~ Mike