Q Why have some of my clematis flowers got green parts on their flowers?
A This is called 'green petal' and it occurs if there is a late cold snap in the spring, while the buds of the plants are forming. It causes some of the petals to become bright green and distorted. Though it might be unsightly, there are no detrimental effects to the plant.
Caption: Green petal looks unsightly but doesn't harm the plant