Commelina communis, if the one in that photo is the same as yours then it's the Asiatic Dayflower. See the link in my previous post for photos and growing information.
That's a good pic, clearly showing C. communis, which has a single lower (clear) petal and brown/maroon dots in the middle of the yellow antherodes. Without such detailed observation, other species look the same at a casual glance. The differences would be lack of the antherode dots, a bifurcated lower petal, and/or slightly different shade of blue, &/or slightly different shape/position of the larger blue petals.
Wow. You two really know your flowers! Purpleinopp, you point out so many details, you make me worried that I picked the correct picture! I am pretty certain that is the one. I'll check next season to make sure. It is a charming flower. I don't plan on getting rid of all of it. We'll see what I can save after pulling the Jumpweed that is growing near it/with it.
Whatever species, it IS cute!! You get to grow what you want in your yard. :+) And I'm also fascinated with flowers you have to "catch" while they are open. Like these, morning glories, 4'o'clocks, Portulaca...
