Of all the plants used in holiday decor, few match mistletoe’s interesting history. And few equal its potential for harm.

An evergreen plant with white berries, mistletoe is quite toxic, said David Trinklein, horticulture state specialist for University of Missouri Extension.

American mistletoe (Phoradendron leucarpum) contains a toxic protein in its leaves and branches. However, mistletoe harvested in the U.S. isn’t as toxic as European mistletoe (Viscum album), Trinklein said. The latter contains a mixture of toxic proteins in all parts of the plant, including its berries.

Unfortunately, mistletoe isn’t usually labeled “American” or “European,” and only a trained botanist would be able to identify the difference, he said. In either case, if the plant accidentally is ingested it would be wise to seek immediate medical attention.

Trinklein said the safest choice would be to use artificial mistletoe made from fabric or plastic.

Mistletoe is a hemiparasite, which means it derives some of its food from its host—most often a tree—while carrying on photosynthesis to make the remainder of its food, he said.

Mistletoe’s mysterious powers go back to ancient times

So, how did a toxic, hemiparasitic plant like mistletoe become a part of Christmas? “From the standpoint of human usage, mistletoe has a long and interesting history dating back to ancient times,” Trinklein said.

“The use of mistletoe around the holidays dates back to pre-Christian times, when it was used by Druids in rituals associated with the winter solstice,” he said. “After being harvested by Druid priests with a golden sickle, people placed it over their door as a means of warding off evil in the coming year.”

A cure for war on the battlefield and at home

Where did kissing under the mistletoe begin?

“Various theories exist,” Trinklein said. “In Scandinavia, it was considered a plant of peace under which enemies could declare a truce. Accordingly, mistletoe offered a way for warring spouses to kiss and make up. Each time a kiss was exchanged under the mistletoe, a berry had to be plucked. Once all the berries were gone, the plant lost its magic.”

‘Dung on a twig’ in a former life

What about the name? The word mistletoe, comes from two Anglo-Saxon words that, literally interpreted, mean “dung on a twig,” Trinklein said. This less than romantic name originated after people observed that mistletoe tended to take root on tree limbs where birds left their droppings.

Many might consider stealing a kiss under mistletoe to be socially and hygienically questionable. “Omitting it from holiday décor probably would be prudent,” he said.

But for those who insist on following tradition, give real mistletoe the heave-ho-ho-ho and use artificial mistletoe instead.

Warning: Mistletoe is highly toxic.

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