Centurea

This was a pretty little flower in our backyard. Love my extension tubes!

https://farm4.staticflickr.com/3747/...8a674e24_c.jpg

I really like where the focal plane is. And I really like the color contrast of the blue/magenta against the green. I think I'm perhaps being overly technically inclined here, but I find that because it's radial, my eye goes to the central portion of the flower and finds it a little too dark there to linger too long.

I quite like this image with its interesting comp. I think I agree with CSB though, a bit of dodging at the center wouldn't hurt here.
I also think I may have included just a bit more of the flower's center on the left side - crop feel a wee bit tight to me.
Still works for me though.

Extension tubes are a lot of fun, and you have used them well here.

You def have the hang of using the tubes. VERY nice.