Brian, I'm not too sure about these. It may be in part that they come over a bit flat compared to what we're used to seeing in your colour macro work. However, it may be more that (a personal reflection here) flowers are good in colour because they are intrinsically colourful, and if you want to do a mono then the structure of the subject is what counts.
I have attached an image here, not as a "how to do it" illustration, but because it is the only B&W that I have kept in the "Flowers" folder in my "Nature" catalogue; I liked it because of the rain droplets and the contrasts provided by the vein structures in the petals.