The whole composition is simply stunning! The way the Sunflowers face away from the sunset, as if they're all travelling back home together. The colours in the Sky that add that extra warmth to the flowers and, well the whole image.
My Only issue is perhaps the horizon, where the Flowers meet the sky, especially where the sunflowers are planted in rows on the far right....
It gives the effect that the image has been placed over the skyline, as it's too bright and sharp against the blue sky and the Flowers appear to be cut off as the rows hit the pinkish cloud. Perhaps a bit of bluring would hinder this affect, or darkening the flowers in that area, it could make the horizons meet a little smoother.

Otherwise the image is utterly perfect,
I think i'll also mention how I like that the largest sunflower at the front isnt quite in focus, so your eye is drawn further into the picture rather then being held at the front row of sunflowers