This is one of those occasions when I feel it’s appropriate to post the original image before I started playing with it. Below you see the shot as it came directly out of the camera. To fill in the story, I shot the image in a 3-exposure bracket, not for HDR but just so I could pick the best one to work with. If you have the card space and the occasion calls for it, this is a useful practice that can work for macros, portraits, street photography, and much more.
This is the underexposed version of the 3 bracket set, and it already creates a dark background, and with the bokeh enhances the separation of the main subject from the background. This was shot in broad daylight on a sunny day, but pointing down into the growth and the ground so the background was not so bright to begin with. Given that start, I played with the black point slider in Aperture which darkened and removed about 80-90% of the visible background. It also darkened and deepened the blue tones of the flower. I decided to extend that a bit more, and pulled the image into photoshop to clean up the remaining extraneous elements. I created a black layer, and just erased the parts of the image that were still visible but didn’t want. I then selective sharpened and added detail to the flowers and call it done.
This led to