I think that there must be yet another form of it in So. Cal. I went to the University of Florida, IFAS Extension and they had this information there:
• Flower color -- The flower color of many dayflower species is blue, while benghal dayflower is more purple/lavender.
• Root structure -- Unlike all other dayflower species, benghal dayflower produces underground flowers. These flowers are easily seen by examining the roots. These flowers will appear as “swollen nodes."
The Commelina in my yard is true, sky blue without any purple or lavender undertones. Also, the root structure does not sound correct as there are definitely no nodes. The FAO lists C. Benghalesis as being 10-40 cm. tall (4 to 15.75 inches). Our plant is much taller than that. Some branches are in excess of 4-5 feet.
I am very happy, though, to finally have a name for this plant. I am hopeful that, as I work my way through the list of known types, I will come across one that fits. Even if I don't discover its full name, knowing that it is a Commelina is great