It seems that the Granny tradition has a more direct provenance back to English/Irish traditions (just like bluegrass music etc.) and shares an American Indian component as well. I found a few articles, but this one seems to have the most info:

http://www.witchvox.com/va/dt_va.html?a=usnc&c=...

It is absolutely a “folk magic” tradition in the sense that it is defined by it's geographic location. To this day Appalachian culture is shot through with customs, crafts and arts that developed in the isolation of mountain culture etc. Folk magic can also be a tradition that is specific to an ethnic group etc.

Here's the Wiki: http://en.wikipedia.org/wiki/Folk_religion#Magic

Think of the concoctions that granny on the Beverly Hillbillies liked to cook up. That sort of folk magic.

If you aren't familiar with the site there are a number of great books there. I love that
they have lots of odd selections – like this one – that would never show up on a contemporary
book list etc.

I'll try to sprinkle more around these parts in the coming months.