I have (in my lazy gardening) come across a lovely discovery! Let that cilantro grow!
There are three reasons for this:
One- aren't those flowers sweet?
Two- if it self seeds, you will have cilantro as cilantro in the fall. (And if it never freezes, you can harvest the leaves all winter!)
Three- If you harvest the seed, (which for some reason changes the spice's name to coriander) you can use it to add perfumey elements to indian, middle eastern and mexican foods. I toast it with cumin seed, crush it, and keep it on hand to add to anything I'd normally use cumin in.