COMPOSITION
The triangular arrangement of these flowers helps to add strength and stability to this composition. I think a broader or larger crop would have helped in that you could have then placed the flowers somewhere in the frame than just barely off of center. That may have helped to give a more dynamic, balanced feeling to the shot.
TECHNIQUE
The colors in this are wonderful. I love the deep hues of the purplish-pink flowers. I also think the green is a deep, rich color. I am undecided on the background color. Part of me likes it because it is different, and provides an interesting contrast with the leaves and color. The other part thinks it might cause just a bit too much "clash" with the purple hues. Also, the shadows are very distracting. I think a slower shutter speed, with the camera on a tripod, may have helped you . Or, perhaps you could have moved the subject away from the background.
OVERALL EFFECT
I think you have chosen a good subject for this challenge, but the areas mentioned above help chisel the effectiveness away from the shot.
Flat lighting makes this look like a funeral piece. The highlights on the greens surrounding the flowers are unsightly as well. Good subjects for this challenge really, but not particularly well executed.