Hey Cath. Probably not what you want to hear, but the answer is, just because they do! That is, this plant's flowers often have exactly one purpleish flower in the middle of the umbel of white ones. Who knows what advantage this particular adaptation serves or served somewhere/sometime in the history of this species? Not I!

+oM

I have a simple theory on that...basically the QA umbel is multiple flowers as evidenced by the way the seed forms.

I think the central purple flower helps to attract insects as it mimics a fertile area (stigma/stamens) in a simple flower. Somewhat like floral guide lines work....go here for food..etc.

In my lifetimes, I've never been a daucus carota, so I could be wrong on my theoretical assumption here. Anyone who feels they have been a carrot in a past life, feel free to speak up :)

The legend behind it says that while tatting lace, making the white part of the flower, the queen pricked her finger and the tiny dark flower in the middle is supposed to represent the drop of blood.

Skibby

Ya'll do know this weedy plant is not a native don't ya? That purple flower on some is to let you know its European and not a native in the wild carrot family and that it should be pulled before it infests the whole meadow. I do feel fairly certain I was a Rattlesnake Master in a past life, which is an American native wild carrot. You can let that one grow.