A little of everything that a thistle plant has to offer.
Spent a lot of time experimenting with reflectors - different colors (silver, gold, white, black) & locations - to handle the sunlight shining brightly on the left side of the plant. The bottom, front & right side of each blossom was heavily shaded and looked almost black without some light reflected back into it. Conclusion - don't make shots like this without some sort of reflector; a crumpled sheet of aluminum foil would work just fine. I used an Adorama diffusion disk with a 4-in-1 cover. Gold & silver were both effective; white was marginal and black (just as an experiment) actually seemed to absorb light as the shadows were darker than with no reflector at all.