In cultures across pre-Christian Europe, mistletoe was seen as a representation of divine male essence (and thus romance, fertility and vitality).
According to Pliny the Elder, the Celts considered it a remedy for barrenness in animals and an antidote to poison.
When Christianity became widespread in Europe after the third century AD, the religious or mystical respect for the mistletoe plant was integrated to an extent into the new religion. In some way that is not presently understood, this may have led to the widespread custom of kissing under the mistletoe plant during the Christmas season. The earliest documented case of kissing under the mistletoe dates from 16th century England, a custom that was apparently very popular at that time.
Winston Graham reports a Cornish tradition that mistletoe was originally a fine tree from which the wood of the Cross was made, but afterwards it was condemned to live on only as a parasite.
Mistletoe is commonly used as a Christmas decoration, though such use was rarely alluded to until the 18th century. Viscum album is used in Europe whereas Phoradendron serotinum is used in North America. Both are commercially harvested. According to custom, the mistletoe must not touch the ground between its cutting and its removal as the last of Christmas greens atCandlemas. It may remain hanging throughout the year, often to preserve the house from lightning or fire, until it is replaced the following Christmas Eve. The tradition has spread throughout the English-speaking world, but is largely unknown in the rest of Europe.
The type of Mistletoe used during Christmas celebrations is of the same type as that believed to be held sacred by ancient druids, but, outside northern Europe, the plant used is not of the same species. The mistletoe that is commonly used as a Christmas decoration in North America (Phoradendron flavescens) grows as a parasite on trees in the west as also in those growing in a line down the east from New Jersey to Florida. In Europe, where the custom originates, the 'original' mistletoe, Viscum album, is still used. The European mistletoe is a green shrub with small, yellow flowers and white, sticky berries which are considered poisonous. Ancient druids considered the Viscum album plant holy, but had no knowledge of the Phoradendron flavescens. Modern druids focus on the parasitic habitat on oak (where it is very rarely found) as being the definer of a sacred mistletoe, and use Phoradendron flavescens as well as other mistletoe species.
According to an old Christmas custom, a man and a woman who meet under a hanging of mistletoe were obliged to kiss. The custom may be of Scandinavian origin. It was alluded to as common practice in 1808 and described in 1820 by American author Washington Irving in his The Sketch Book of Geoffrey Crayon, Gent.:
The mistletoe is still hung up in farm-houses and kitchens at Christmas, and the young men have the privilege of kissing the girls under it, plucking each time a berry from the bush. When the berries are all plucked the privilege ceases.