I like how the background, being completely washed out causes your eye to roam ONLY over the subject. And the way the sunlight shining thru the leaves and petals accents their structural details. AND, as you say, it gives it a watercolor effect to boot. Then again, I'm a fan of watercolor in art, so I guess I'd be partial to it for that reason. What is the blue in the image? Looks like it could be a bottle or vase on the windowsill? Whatever it is, just that little touch of additional color is a perfect balance with the red and green. This is just a terrific picture!