I’ve also heard this called ‘Mexican Pansies’.
These flowers grow from thick stalks that are about 1/2″ in diameter. The stalk is soft and easily broken.
It loves hot and sunny locations, although I have some growing in a mostly shaded area too. The more sun this plant gets the more flowers you’ll have. The flowers are purple and Mexican petunia will bloom through most of the summer. The flowers are well liked by butterflies.
It will grow aggressively in damp areas ( read can be invasive ) but will survive an occasional drought once the plant has settled in and become established.
The roots are shallow so if it becomes a problem you can dig them up with out much trouble.
It will be damaged and die back in a frost. When it dies back it leaves rough, ugly stalks you’ll need to go out and cut down. It will return from the roots once the weather warms up.
It is a good plant for trouble areas, but difficult to remove if you decide you don’t like it.
These are dying off in the extreme heat and drought of summer 2011.
Floridata, Ruellia Brittoniana