When we think of mistletoe, we usually picture a sprig hanging in a doorway, an excuse for an awkward kiss, or a cozy Christmas tradition. But in nature, mistletoe is far less romantic—and far more fascinating.
A Holiday Parasite
Mistletoe is, biologically speaking, a parasite. It attaches itself to a host tree or shrub using a specialized structure called a haustorium. Through this structure, mistletoe siphons off water and nutrients from its host. Unlike true parasites, however, mistletoe can photosynthesize, producing some of its own energy. This makes it a partial parasite rather than a fully dependent one.
Mistletoe species can grow on a wide variety of trees. Some hosts show little effect, but others suffer reduced growth, stunting, loss of outer branches, or—in cases of heavy infestation—even death. One species in particular, Viscum album, is remarkably successful, capable of parasitizing more than 200 different tree and shrub species.
Bird Poop on a Twig
Mistletoe has small, oval evergreen leaves and produces waxy white berries. Its name has a surprisingly literal—and unglamorous—origin. It likely comes from the Anglo-Saxon words mist or mistel (meaning manure) and tan or toe (meaning twig or stick).
Why such a name? Because birds are essential to mistletoe’s life cycle. They eat the berries, fly elsewhere, and “deposit” the seeds after digestion. The seeds are coated in a sticky substance that glues them to whatever branch they land on, where they can sprout and grow. In other words, mistletoe roughly translates to “bird poop on a twig.”
Medicine, Magic, and Mild Toxicity
Despite its festive reputation, mistletoe is mildly toxic to humans. Still, for centuries it has been used in traditional medicine to treat ailments ranging from worms and leprosy to labor pains and high blood pressure. In parts of Europe today, injections of mistletoe extract are prescribed as a complementary therapy to help reduce side effects of chemotherapy in cancer patients.
Beyond medicine, mistletoe has long been steeped in symbolism. The ancient Druids considered oak trees sacred and believed mistletoe growing on them was a divine gift. They harvested it for winter solstice rituals and decorated their homes with it. The Romans associated mistletoe with peace, love, and understanding, hanging it over doorways to protect households. In medieval Europe, it was believed to ward off witches and ghosts when placed over the doors of homes and stables.
From Folklore to Kissing Tradition
By the eighteenth century, mistletoe had firmly embedded itself in Christmas celebrations. The first known reference to kissing beneath it appears in a 1784 English poem. In Victorian England, the tradition was popularized among the servant class, with rules attached: a man could kiss any woman standing under the mistletoe, and it was considered bad luck for her to refuse.
The custom crossed the Atlantic largely thanks to Washington Irving. His bestselling book The Sketch Book included a series of Christmas stories depicting an idealized English holiday season. In one chapter, “Christmas Eve,” Irving described mistletoe hanging in farmhouses, allowing young men to steal kisses from young women. With each kiss, a berry was removed from the sprig, and once the berries were gone, the kissing had to stop. The book’s popularity helped cement the tradition in American culture.
A Modern-Day Mistletoe Hunt
Today, mistletoe still plays a role in regional traditions. In the southern United States, mistletoe hunting is a time-honored winter activity. Harvesters sometimes shoot bunches down from trees, selling them as holiday decorations. The plant’s cultural significance is so strong that mistletoe is even the floral emblem of the state of Oklahoma.
So the next time you find yourself standing under a sprig of mistletoe, remember: you’re not just beneath a symbol of romance, but under a parasitic plant with a history rooted in bird digestion, ancient ritual, folk medicine, and centuries of storytelling.