Alyogyne huegelii ( Blue Hibiscus ) is a show stopper in the garden this time of year because of it's intense purple flowers (it comes in a number of shades of purple as well as white). Oddly enough, it is not really blue or a hibiscus, but a member of the lilac family. It was once in the hibiscus family and everyone knows that gardeners call purple blue, thus the name. It grows easily in Southern California, maybe a bit too easily because it is hard to keep it looking neat and compact.
It is one of those plants that needs almost weekly pruning. It will get out of control if you go a couple weeks without looking at it and then it is hard to get back into shape without sacrificing a great number of blooms. My advice? Plant it where you walk by it everyday so you can remember to cut it back regularly, and so you can admire those beautiful blooms!