Thanks, guys.
I think Centaurium scilloides is the likely answer since it's clearly something I have growing in a trough already but the trough is on my sunny patio. I guess it's possible it reseeded itself into my rock garden. The picture I posted of C scilloides has 6 petals which would correlate with my mystery plant. Unfortunately I've been out of town this week, so I may miss the opening of the new buds. I'll check them out when I get back in town. Thanks for your help!
