One way to grow Black Roses is to water the rose plant with water mixed with black food coloring, gradually darkening the blooms.
There are several rose varieties that have the word black in their name, like Black Magic and Black Prince, but there is no rose plant that will naturally produce truly black flowers. Instead, what is usually called a black rose has very dark red blooms, often with petals tinged with an even darker shade at the edges. Black Roses of this kind often produce flower buds that look almost black, but as the blooms open, the red or purple color becomes more visible.
It has been reported that botanists already have created truly Black Roses in laboratories by manipulating the genes of rose plants, but such a rose plant has not yet been made available to flower growers or the public.
Through cross-breeding, cultivators have been able to produce the very darkly colored rose varieties referred to as black roses. Two of the most well-known and most darkly colored black rose varieties are Black Baccara and Black Jade. Both these roses are a very dark, bluish-black shade of red, and are darkest in color before the blooms open. These varieties of black roses are most commonly available from plant stores and nurseries specializing in roses.
In order to produce as darkly colored blooms as possible, some rose growers suggest growing black roses in somewhat cooler and shadier conditions than other kinds of roses. Growing these roses in a greenhouse, where growing conditions can be more tightly controlled, can help produce darker flowers.
It is possible to darken the color of the blooms of black roses further by adding one teaspoon of black food coloring or dye to five cups of water, and watering the plant with this mixture once a week. The color is absorbed by the roots and will eventually darken the color of the flowers to black.