The genus Circaea contains 7–10 species of flowering plants, known as Enchanter's nightshade, in the willowherb family Onagraceae. They are woodland plants occurring throughout the temperate regions of the Northern Hemisphere. Two species are widespread, Broad-leaved Enchanter's Nightshade (Circaea lutetiana) and Alpine Enchanter's Nightshade (Circaea alpina). In addition, there is an intermediate hybrid between these two, and several local species or subspecies, with between eight and 14 forms recognised by different authorities. The hybrid is sterile, persisting only by vegetative reproduction and not producing seeds.