Roses in rare colors such as blue and black have symbolic meanings to match their odd hues. The black rose in particular has meanings that can potentially create misunderstandings between you and the recipient.
Not Really Black
A black rose that is actually black hasn't been discovered. What passes for black roses are either dyed, or they're red roses with such a deep color that they can look like they're black. A black rose is often darker in bud stage, opening up to show a dark red or scarlet flower. The ends of the petals may be tinged with black and tend to have a velvety sheen. Some have little fragrance. The true red color of black roses can create confusion, as someone might mistake them for regular red roses.
Meaning and Considerations
Black roses, whether a dark red variety or artificially colored, generally represent death, farewells and endings. Of course, those could be negative or positive depending on the situation. For example, a new stage in a project or in life sometimes requires the "death" of the old stage, and the website Sensational Color says that some may see a black rose as representing "rebirth or the beginning of something new." Black roses, because some manipulation might be involved in getting it to a particular shade, can also mean obsession. Be aware, though, that giving someone a black rose generally indicates the end of the relationship.
Black rose symbolism itself isn't new, although the uses have changed somewhat. TattooSymbol.com notes that the black rose was the subject of a song sung by Irish troops fighting the English as far back as the 1600s. It has been used as a symbol for anarchist and other antigovernment organizations as well.
Roses with this color don't grow by chance. Several cultivars exist that are suitable for home gardens, and to make it simple, they tend to have the word "black" as part of their names, such as 'Black Ice,' 'Black Beauty' and 'Black Jade.' No standard meaning regarding growing black rose bushes seems to exist, although you probably don't want to give a potted black rose bush as a gift. These varieties are usually cold hardy to zones 4 and 5, depending on the variety, and suitable for growing in up to zone 9. 'Black Jade' is an exception, with the ability to grow in zones 10 and 11. Bush height ranges from 2 to 10 feet.
If a black rose is still too red for you, and you wonder if the recipient or anyone looking at the rose might think it a plain red rose--thus missing the point--Rose-Works.com suggests placing black dye in the water to make the black roses seem blacker. This is the same procedure some school experiments use to illustrate flower petal xylem systems. The flower will draw the dye up along with the water, and eventually the dye should appear in the petals. How much of the dye will make it up to the petals, or actually make the flower look darker, will depend on the individual flower.