If you want the sunflowers to be the main focus of the painting, then you need to give them MORE IMPORTANCE - in terms of the amount of space they take up as a shape - than the sky. Designing the shapes within the rectangle is really important, and having a 50/59 split between sunflowers and what is above them, diminishes the sunflowers.
I am not sure what is going on in the picture. Is there supposed to be a row of trees behind the sunflowers - with a brushed-off sky above?
I am sorry, but I have to disagree with David, I don't think it works as is.
But if you like it, then consider the idea of cropping to make the sunflowers take up more of the space.
And here is my take on it..........
it's a bit "photoshop blurry" but you get the general idea.