Hi,
We had a discussion about this earlier in the year. Hopefully the info on the link helps : )
Remy

Here is a link that might be useful: Ruellia Post

If nothing else, you could dig up some and overwinter indoors. I received some free in a purchase year before last and liked them so brought them in. They survived pretty well indoors, long enough to plant outdoors the next year (I'm not that good with indoor plants so they really are fairly hardy). They went back outside when it was warmer last year and did fine. I did get seed pods/seeds from them, the description in the other link seems familiar. I remember having to pick the pods after they got hard and dark and dryish, but before they popped open; cover whatever container you put the pods in or they'll end up all over the counter/floor. ;] Despite their hardiness, all the seed I got went to swaps; I don't know the germination rate on them. I did not intentionally grow them again, and no volunteers came up here that I'm aware of.

Good luck!
Terri :]