I agree, in general most flower shots are better with backgrounds that reflect their environment. However, one still has to be mindful of how it all looks together. No different than not accepting trees and poles growing out of people's heads. If you don't care about the documentary aspects of the image, I would just select swaths of surrounding dark areas, copy, and paint out the white areas. right now it just don't look that natural. But bw is not natural anyway.
JR