Mistletoe is hung in doorways at Christmas as an invitation to kiss. The tradition likely traces back to Norse mythology and ancient beliefs about the plant’s power to promote peace, fertility, and protection from evil. Today it’s mostly a lighthearted holiday decoration, but the plant has a surprisingly rich history spanning Druid rituals, Scandinavian legends, and even modern cancer research.
The Kissing Tradition
The custom of kissing under the mistletoe is the plant’s most famous Christmas role, though pinpointing exactly where it started is difficult. One strong thread leads to Norse mythology. An old Norse legend held that mistletoe hung in the house would keep feuding spouses from becoming too hostile toward each other, a “kiss and make up” idea that may have evolved over centuries into the romantic tradition we know today.
A related Scandinavian custom had a more dramatic rule: when two enemies met beneath a tree bearing mistletoe, they were duty-bound to lay down their weapons for a day. That association with truces and goodwill fit naturally into the spirit of Christmas celebrations.
There’s also an older etiquette most people have forgotten. Traditionally, a berry was supposed to be plucked from the sprig for every kiss exchanged beneath it. Once all the berries were gone, the mistletoe’s “kissing power” was spent.
The Norse Legend Behind It
The mythology that most directly connects mistletoe to love and reconciliation is the story of Balder, one of the best-known tales in Norse tradition. Balder’s mother, the goddess Frigg, extracted a promise from every living thing that it would never harm her son. Fire, water, iron, stones, trees, poisons, animals: all swore the oath. But Frigg skipped the mistletoe, thinking it too young and insignificant to matter.
The trickster god Loki discovered this oversight, fashioned a weapon from mistletoe, and guided the blind god Hother to throw it at Balder. The mistletoe struck and killed him. In one version of the story, Frigg persuaded the other gods to restore Balder to life and repaid them with kisses. The mistletoe was then made to promise it would never again do harm and would instead be “consecrated to acts of happiness and usefulness.” Frigg, goddess of love and beauty, was given authority to hold the plant to that pledge. The connection between mistletoe, kissing, and goodwill flows directly from this story.
Druids, Churches, and Holly
Long before Christmas traditions existed, the Druids of ancient Britain and Gaul revered mistletoe. The Roman writer Pliny the Elder recorded that Druids considered nothing more sacred than mistletoe growing on an oak tree, which they viewed as sent from the heavens. When found (it was apparently rare even then), it was harvested with elaborate ceremony on the sixth day of the moon cycle using a golden sickle. Two white bulls were sacrificed beneath the tree, and the plant was believed to cure poisons and grant fertility to sterile animals.
People placed harvested mistletoe over their doorways to ward off evil in the coming year. But this deep association with pagan ritual created a problem once Christianity spread through Europe. Early Christian churches banned mistletoe from their decorations and encouraged followers to use holly instead. That substitution is actually how holly became a Christmas symbol in its own right.
The Plant Itself
The mistletoe you see sold at Christmas is a partial parasite. It grows on the branches of host trees, most commonly apple trees, and taps directly into the host’s water and nutrient supply through specialized root-like structures. It does photosynthesize on its own, so it produces some of its own energy, but it steals water and minerals from its host. Heavy infestations can reduce a tree’s ability to photosynthesize and grow, and when multiple mistletoe plants colonize the same branch, the damage compounds.
Two main species show up during the holidays. In Europe, the classic Christmas mistletoe is Viscum album, recognizable by its white berries (the word “album” means white). In the southern and eastern United States, the common species is Phoradendron leucarpum, sometimes called American or eastern mistletoe. The two look similar and serve the same decorative purpose.
Ecological Value
Despite being parasitic, mistletoe plays an outsized ecological role. A landmark experiment in Australian woodlands tested what happens when mistletoe is removed entirely. Researchers stripped all mistletoe from 17 woodland sites and monitored bird populations over three years. The results were striking: those sites lost nearly 21 percent of their total bird species, 26.5 percent of woodland-dependent species, and almost 35 percent of resident woodland birds. Control sites where mistletoe remained saw moderate increases in diversity over the same period.
The primary mechanism appears to be nutrient enrichment. Mistletoe drops nutrient-rich litter to the forest floor, creating patches of higher productivity that support insects and other food sources for birds. Many bird species also nest directly in mistletoe clumps. This pervasive influence on biodiversity has earned mistletoe the designation of a “keystone resource” in ecology.
Toxicity Concerns
The white berries that make mistletoe look festive are mildly toxic to humans and more dangerous to pets. The plant contains proteins and compounds that can damage cell membranes, inhibit protein production in cells, and interfere with DNA synthesis. Ingestion typically causes irritation of the mouth and digestive tract, vomiting, and diarrhea. More serious symptoms can include changes in heart rhythm, fever, fatigue, skin rashes, and in rare cases, convulsions. Repeated or chronic ingestion can damage the liver and lower blood pressure.
If you have small children or pets, hanging mistletoe high and out of reach (or using artificial versions) is a simple precaution. Most holiday exposures involve only a berry or two and produce mild stomach upset, but the risk is real enough to take seriously with cats and dogs, which may chew on fallen sprigs.
Mistletoe in Medicine
European mistletoe extract has been used as a complementary cancer therapy for decades, particularly in Germany and Switzerland. Pharmaceutical preparations are given by injection alongside conventional treatment. A systematic review of controlled clinical trials found that eight studies showed a statistically significant survival benefit, and several others found improvements in quality of life, including reduced side effects during chemotherapy and radiation. Side effects from the extracts themselves were generally minor: redness or itching at the injection site and mild flu-like symptoms.
This medical use is far more established in Europe than in North America, where it remains outside mainstream oncology. The same compounds that make the raw plant toxic, particularly the lectins and viscotoxins, are the basis for these therapeutic extracts, processed and dosed in controlled ways that bear no resemblance to eating a berry off a holiday decoration.
How Holiday Mistletoe Is Sourced
The commercial mistletoe trade is surprisingly recent, dating only to the mid-1800s when the kissing tradition became widely popular across Britain. Most of the UK’s supply comes from a handful of counties in western England: Herefordshire, Worcestershire, Gloucestershire, and Somerset. Harvesters gather “wraps” of mistletoe primarily from apple orchards, where the plant thrives on older trees. The best-known trading center is Tenbury Wells, on the Worcestershire-Herefordshire border, which has hosted wholesale mistletoe auctions for over a century.
Domestic supply in Britain has never fully met holiday demand. Imports from mainland Europe, especially from apple orchards in Normandy and Brittany, have supplemented the market since the Victorian era. In the United States, wild-harvested American mistletoe from southern states fills a similar seasonal niche, though artificial mistletoe has increasingly replaced the real thing in many households.