Nice photo...but there's a couple of things bugging me. The crop, it's too tight. You actually clip a bit of the flower on the right side, and that's a definite no no, you don't want anything leading the viewers eye out of your picture. Moving a bit backwards would've fixed this. Not too much though, because too much empty space on the sides of the flower wouldn't have worked very well either. The fact that the image is a square would leave me to believe that it was cropped, and if this is the case and you still have the original this can be easily fixed.

Another thing is the composition, it would be nice except for the tree in the background. That blob of dark space against the warm sky draws the eye away from the focus of the shot, which as I stated above is something you never want.
Some changes of your position could have cleared the tree and still left you with an almost identical composition.

All in all nice work but it still needs some tweaking, you're getting there though

The back lighting technique works so well here. I love how you can see all of the little details of the flower's stem. I also like how the sun is so white because of its brightness. It makes the stem of the flower pop but it also sets off the petals because the petals are so dark, you can't help but look at them.

I think a little bit more sharpness would've worked out well here, as well as a tiny bit more contrast. I'd suggest the added contrast simply to really set off the back lighting even more than what was done naturally. Overall though, this is a really beautiful image.