Mostly its going to be composition and lighting. A single flower has a natural compositional balance, but multiple flowers have to be worked on. After you get that sorted out, here is an idea. One thing I like to do is shoot at minimum focal distance wide open. Backgrounds tend to melt and/or have interesting effects. This fits my style which is somewhat the opposite of realistic. YMMV here, but I think each lens has an ideal subject size at MFD, within the bounds of post processing cropping and that can be found through experimentation. So, here are three very different lenses at MFD, wide open with pretty different results.
The Formula 5 135mm 1.8 may be one of the worst lenses in the world wide open. Nonetheless it produces interesting results. Wide open at 1.8 MFD
Canon FL 55mm 1.2 An antique also wide open
Spiratone Plura-Coat 24mm 2.8 wide open