bizarre, plants

Mistletoe: A Parasitic, Poisonous Plant

Have you ever wondered why it’s a tradition to hang up some mistletoe around this time of year and kiss under it? Or what about the mistletoe plant itself – where does it normally live when it’s not hanging above our doorways? While we now often associate this tradition with Christmastime, like many “Christmas traditions,” the idea of kissing under mistletoe, or having reverence for the plant, likely existed long before it was assimilated by Christianity. Specifically, it’s thought that the tradition may have its roots in centuries-old Norse mythology (or even earlier practices).

mistletoe tree
A “shrub” of parasitic mistletoe can be seen growing on a branch in this tree. (Image credit: 663highland)

The most frequently associated mythological story is how Loki, that infamous Norse god of mischief, tricked another god into using a projectile made of mistletoe to kill Baldur, the son of a Norse goddess, Frigga. Some propose that because of the tragic myth, people were told to henceforth only let mistletoe bring about love instead of death, and the kissing tradition came from this. But the kissing tradition may have had other origins; for example, the mistletoe plant has been long associated with fertility, appears in ancient Greek mythology, and was considered sacred by ancient druids when collected from oak trees. Why so much focus on the mistletoe plant? As it turns out, biologically it really is a fascinating, and unique, kind of plant.

The name “mistletoe” actually refers to hundreds of different species (spanning several families) of evergreen, partially parasitic plants that are poisonous to varying degrees. These plants live up in the branches of trees or shrubs and, amazingly, jab a special type of root (called a haustorium) into the host plant to suck out water and nutrients from it. The European mistletoe (Viscum album), which has oval-shaped leaves and white berries, is the “original” mistletoe plant of European mythology and reverence, and it’s the only mistletoe species throughout most of Europe. Many of the other mistletoe species live in tropical and subtropical climates in different parts of the world. (Interestingly, although we often think of “parasites” as being unwanted, studies have found that the presence of mistletoe plants actually improve the biodiversity around them.) Depending on the exact species of mistletoe, upon consumption the plant may cause gastrointestinal distress, blurred vision, a low pulse, and possibly death, which is why it’s recommended to call poison control if any part of the plant is consumed.

So if you find yourself standing under some mistletoe this holiday season, you could reflect upon what odd circumstances lead to it being a seasonal tradition to hang a poisonous, parasitic plant in our houses and kiss each other under it. At least the plant serves a better use this way than it did in the hands of the cunning Loki.

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