The specific term references a type of heuchera, also known as coral bells, frequently sold at home improvement retailers. These plants are characterized by their deeply colored, often near-black or dark purple, foliage. As an example, a homeowner might purchase several of these plants to provide a dramatic contrast in a garden bed containing lighter-colored flowers or foliage.
The popularity of cultivars with such coloration stems from their aesthetic value in landscaping and container gardening. They offer visual interest throughout the growing season, even when not in bloom. Historically, plant breeders have focused on expanding the color palette of heucheras, leading to the introduction of many varieties, including those with very dark leaves, which are now widely available.