Overwintering Mexican Petunia (Ruellia simplex) in Georgia: Dieback, Companions, and Invasiveness

Q: I had Mexican petunia first time this year. Leave out for winter or take inside?

Mexican petunia (Ruellia simplex) grows well outdoors in Atlanta. Might not be winter-hardy in north Georgia. Blue flowers attractive late summer-fall. Stems die back after first frost. Rather than bare area, I plant iris, hardy amaryllis, daffodils in their spot. Common "tall ruellia" can be invasive unless contained. If planted at one end of a big bed, it spreads a couple feet yearly. Dig unwanted sprouts every May. Improved shorter varieties like 'ChiChi' and 'Purple Showers' might be less cold-tolerant.