Q: I had Mexican petunia in my flower garden for the first time this year. Can I leave it out for the winter or do I have to take it inside?

A: Mexican petunia, Ruellia simplex, should grow perfectly well outdoors in the Atlanta area. It might not, however, be winter-hardy in north Georgia. The blue flowers are attractive in late summer through fall. The stems will die back to the ground after the first frost. Rather than leave a bare area for winter, I plant iris, hardy amaryllis, and daffodils in their garden spot. Be aware that the common “tall ruellia” can be a bit invasive unless contained. If you plant it at one end of a big flower bed it will spread a couple of feet outward each year. Dig and remove unwanted sprouts every May. There are several improved and shorter ruellia varieties on the market, like ‘ChiChi’ and ‘Purple Showers’, that might be less tolerant of cold than tall ruellia.