During the geological evolution, the predecessors of today's Helleborus probably spread west from Southeast Asia, along the ancient Mediterranean Sea. As warm and cold periods alternated during that time, hellebores developed the ability to delay, or even interrupt, their growth and flowering period. Another remainder of that time is their more or less strong ability to lower the pressure inside their cells in response to frost. This effect can be reversed as temperatures rise. You can observe this phenomenon quite well on a morning after a frosty night when the leaves and flowers are bent towards the ground and, as the day unfolds and temperatures climb, gradually rise to their upright positions. 

Distribution of the Helleborus genus is limited to the northern hemisphere including Europe and Asia. Helleborus species are most highly concentrated along the Baltic Sea, but some species are also native to places along the coasts of the Black Sea. 

Only two species, H. vesicarius and H. thibetanus, are of different origin. H. vesicarius grows in the border region between Syria and Turkey. H. thibetanus is native to China.