The poinsettias have a similar problem to a person's face - when you use bounce flash off the ceiling, there are shadows in the areas that can't 'see' the light from the flash. This is typical of a person's eye sockets. I therefore added my second flash to hit the flowers from the front, while my second flash bounced off the ceiling. I took a series of 7 shots to go from 8:1 through 1:8. You can see how the fill flash on the leaves goes from non-existent to overpowering as I run through the ratios. Also the room in the background gets less and less lit as the front flash goes up in comparison.
8:1 (bounce to fill)
This one is getting some detail in the leaves underneath, but starting to cast shadows on the leaves as well. I had the flash to the left of the camera so this could be avoided if I had put the flash on axis, and slightly above the camera position.
Here is a quick setup shot, with the front flash shown on the couch next to my camera position. The other flash is on the end of the fireplace mantel - next to the lampshade. My exposure was short enough in shutter speed to not pick up any ambient light in the shot.