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any species of the genus Empetrum, of the heath family (Ericaceae), particularly E. nigrum, an evergreen shrub native to cool regions of North America, Asia, and Europe. The plant thrives in mountainous regions and rocky soil. It grows about 25 cm (10 inches) tall and is somewhat trailing in habit. The narrow, simple leaves are about 1 cm (0.4 inch) long; the sides curl backward until they meet. The solitary flowers are very small and purplish. The fruit, about 1 cm long, is black, berrylike, juicy, and edible but somewhat acid in taste