Holly - more specifically the European holly, Ilex aquifolium - is commonly referenced at Christmas time. In many western cultures, holly is a traditional Christmas decoration, used especially in wreaths and illustrations, for instance on Christmas cards. Since medieval times the plant has carried a Christian symbolism, as expressed in the well-known carol "The Holly and the Ivy". However, the association of holly with winter celebrations almost certainly pre-dates Christianity. Druids wore holly wreaths on their heads.