Cuphea hyssopifolia
Mexican Heather
LYTHRACEAE
This is a very cute, shrubby, evergreen perennial originally from Southeast US,
Mexico, and Central and South America. So it is right at home!
This one is only about 18 inches tall and has half-inch purple flowers most of the summer.
It is also called the Elfin herb, False heather, and Hawaiian heather.
Full sun to part shade, it is supposed to live in zones 10-12 (this one lives in the ground on the border of zones 8 and 9). It is often used as a house plant.
In warmer areas it could become invasive.
Short lived, it re-seeds itself readily. You can also propagate it by division or by rooting softwood cuttings in late spring.
It is prone to whitefly, and aphids.