Your lighting has a lot to do with this, I believe. It looks like you were using continuous lighting here, which has the advantage of being easy to preview and meter, but won't deliver a lot of lighting power relative to inexpensive strobes. I recently shot an Iris outdoors during the day, and I was able to darken the background almost completely by severely underexposing the scene, then adding a strobe at close range (I was shooting Manual, but you might be able to achieve results like this with TTL metering).
As you can see, the strobe adds some highlights and shadows, which give the flower some dimension, and the water droplets add a bit of interest, too. Be sure to soften the strobe somehow to avoid overly harsh shadows - in this case, I used a mini softbox. Below, you can see a bit of the setup for this shot:
Yes, I ended up switching the strobe to camera left for the photo that I wound up keeping, but the overall setup is the same. Note that by using powerful lighting at short range, I was able to so underexpose the background that it darkened nearly completely, even though it was still quite light out (as seen in the setup shot). With your dark background, you shouldn't need anywhere near this amount of overpowering artificial light -- I did this mainly to demonstrate the technique.
As far as post-processing goes, I used Lightroom to process the photo -- I boosted blacks just a bit to completely drive out the remaining traces of the background, then sharpened a bit. You can certainly play with processing to add more "pop", but the closer you can get in-camera, the more authentic the end-result, in my experience.
I wrote this shot up on my blog, by the way, including a second Iris shot done with a white background and more of a high-key look -- again, mainly to illustrate how to control the look of your background using strobes.