This is great plant for our deck. When they say dead heading, do you actuallly remove the whole head? I have tried rubbing the head so that the tiny petals fall off. I think i should be cutting off the whole head? Help. I have attached a photo. You will notice the ones that don't have the little purple flowers. Do i cut the heads completely, cut right down at the base of the plant (at the point where the little bush is) or just rub the heada so the dead little leaves fall off? This is a perfect plant for our deck and want to see them thrive.