Looked around online a bit and see some folks reporting some success at growing ginseng in northern florida.
Some articles suggest zones 3-7 and others 3-8. Wildgrown.com has a article that suggest 3-8.
The text below is from the article/url included below it:
Experts suggest that areas with 50 below-freezing days a year are at the southernmost ginseng growing zone. http://www.a-spi.org/AGF/manual1.htm
Below is one from Univeristy of Florida.
Reports indicate ginseng roots often decay when attempts are made to grow them under warm, humid Florida summer conditions. http://edis.ifas.ufl.edu/vh020
Good Luck !