When photographing wildflowers, I have learned to pay attention to the background to see if it will help or distract from the subject.  In most cases, I find the background more distracting and will opt to move in close with the macro lens in order to reduce the amount of background showing in the frame.  Sometimes, I find that the background really compliments the flowers and I’ll back off a little, including more of it in the frame.  This image was a rare composition for me; the background really made the shot, so I have a frame with mostly background in it and, at some level, it works.

 

The background itself is pleasant enough.  It has the frequently employed out-of-focus (beyond the depth-of-field) effect, provided by a large aperture of f/4 on a 100mm lens; this produces a soft/sharp focus contrast.  However, what really makes this background work well is that it is in shadow while the subject is in direct sunlight, creating a dark/light contrast that helps accentuate the foreground flowers.

 

When lighting conditions aren’t this good naturally, you can accomplish a similar effect with a flash.  Here, you would want the flash to dominate the exposure, and you should set the flash  to produce from 1 to 3 f-stops more light than ambient (and remember to expose for the flash’s light, not the ambient light).  Using the flash off-camera and held above the subject will be more consistent with the natural direction of sunlight, but straight-ahead can also be successful.  When using the flash, keep in mind that the transition from light to dark will be more gradual as the illumination level decreases with (the square of) the distance from the flash; the transitions in illumination with natural light can be more distinct with hard-edged shadows.