Here are seven more photos of purple irises. The first five were shot a few days ago using the lens that I usually grab for close work, a Canon 100/2.8 L IS macro. I used a hint of off-camera flash to add sparkle to the dull daylight. The flash was behind the flower, to the left and above, just out of frame.
In the first example, a narrow aperture gets almost all of the subject in focus, but leaves the background looking a little busy, though maybe not objectionably so in this case.
I experimented, using a wider aperture to soften the background, and stacking (blending) several exposures focused at different distances to get most of the flower in focus.
Moving in closer, the high magnification ensures that depth of field will be shallow no matter what the f/stop.
The last of that series is close to life-size in camera (larger than life on your monitor).
These last two were done today, with just natural daylight. In order to turn the distracting, detailed background into a wash of soft color, I used a very long focal length: 600 mm, achieved by attaching a 2X tele-extender to a 300 mm lens.