The terminology "black flowers" is used loosely to refer to the darkest blooms available to growers. If you look closely, you'll usually see that "black flowers" are such a deep purple that they just appear black. I show pictures of black flowers, as well as an example of a plant with dark foliage, in this photo gallery.
|Purple Morning Glory: Almost Black Flowers||Dark Coleus Photo||Dark Foliage of Ajuga||Edens Magic Giant Bergenia Photo|
|Picture of Sand Cherry||Shrubs With Dark Foliage: Smokebush|