C. alpina and C. canadensis. The hybrid is sterile but spreads vigorously by vegetative means. Distribution Members of genus Circaea occur throughout the temperate and boreal forests of the Northern Hemisphere, from near sea level to altitude, and from 10°–70° N latitude. Circaea alpina is the most widespread species, ranging across North America, Europe, and Asia. Likewise Circaea canadensis ranges across continents, in North America, European Russia, and Asia. Circaea lutetiana occurs throughout Europe, ranging eastward to Iran. Three taxa are known to occur in North America: Circaea alpina, Circaea canadensis, and the hybrid Circaea × sterilis. C. alpina is wide ranging across the continent, from California to Alaska in the west, and from Newfoundland to North Carolina in the east, while C. canadensis is confined to the eastern half of North America. The hybrid, C. × sterilis, is found wherever the ranges of its parent species overlap. References External links Natural England. Accessed July 2011 English Country Garden Accessed July 2011 Plant Identification UK Accessed July 2011 Taxa named by Joseph Pitton de Tournefort Plants described in 1753 Taxa named by Carl Linnaeus Onagraceae genera