when shooting with a white background, you should move the subject away from it. basically, take a white sheet, and put the flower in a vase. Make sur ethe subject and background are far enough away from each other so you don't get a shadow. :) Keep shooting, this is not meant to be a bad comment, only a little tip!
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A beatifully clear photo. nicely cropped and center. Good exposure. I wonder if moving the backdrop further away might have elliminated those distracting shadows? Perhasp some of the white flowers could have been trimmed to keep everything inside the frame?
I don't like the shadow that some of the stems leave on the background, they are confusing to the eye, making it look like it is out of focus; other than that a very nice shot, the rose seems sharp with pleasing color
If I could advise something, I would recommend to put the flower horizontal, or at least away from the background. Because it's so close this pic is spoiled by unnecessary shadows made by flash.
Also using an external source of light would help. Sory if I'm wrong, but I think you used flash and that makes the pic flat.
Still a nice composition.